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MPT 185088
  • Female, 39 Years
  • Activity Score354

Dr. U

Associated for 3 Years 5 Months
Teaching Is My Passion
  • I teach at My Home
  • Online
  • Experience:
    I love to teach and have been teaching since quite a long time (around 10 years, since my P.G. days). I have worked in the industry as well (before and after my doctoral period), but I find teaching a more satisfying experien... More [+]
  • Teaches:
    Zoology, English, Chemistry, Biology, Botany
  • Board:
    All Boards
  • Pincode:
    412207
Profile Details
Profile Details

Qualification :

0

Total Experience :

13 Years

I love to teach and have been teaching since quite a long time (around 10 years, since my P.G. days). I have worked in the industry as well (before and after my doctoral period), but I find teaching a more satisfying experience than any other job. I have been teaching Chemistry in a college but currently, I am looking forward to teaching on my own to share more of my knowledge.

Tutoring Option:

I Can Manage Both

Tutoring Approach:

Teaching to me is guiding a student in his/her endeavor towards achieving quality education. It is more about making the student feel comfortable about the subject and not develop unnecessary phobia for that subject or topic. In order to achieve the above mentioned target, I first of all split a particular lesson into smaller sections, teach the concept giving examples and then approach to solve problems based on the concept taught. This makes the student breathe easy while studying. I prefer to teach on a one to one basis and thus limit the batch size to 3-4 students per batch.

Hourly Fees [INR]:

400.00

Class 9 - 10 English, Chemistry, Zoology, Biology, All Boards, All Medium INR 350.00 /hour
Class 11 - 12 English, Chemistry, Biology, All Boards, All Medium INR 400.00 /hour
College Level Botany, Chemistry, Zoology, Biology INR 350.00 /hour
Answer
Answer
  • Question: What is the difference between mixture and compound?

    Posted in: Chemistry | Date: 19/02/2016

    Answer:

    Matter is broadly classified at the macroscopic level into two types of substances - pure substances and mixtures. Pure substances are further classified as elements and compounds.

    A compound is made up of two or more elements combined together in a fixed ratio. Composition of a compound is fixed and its components cannot be separated by physical methods. Examples are - water (H2O), carbon dioxide (CO2), hydrochloric acid (HCl), urea (NH2.CO.NH2) etc.

    Mixture, as the name suggests, is a mix of two or more pure substances in any ratio. The composition of a mixture is variable and its components can be separated by physical methods. Examples are - sugar or salt solution in water, milk, air, oil in water, biscuit etc.

  • Answer:

    Magnetic separation is used to separate iron pins fron sand.

  • Question: What are the various laws of chemical combination?

    Posted in: Chemistry | Date: 19/02/2016

    Answer:

    The laws of chemical combination are as follows -

    • Law of conservation of mass
    • Law of definite/constant proportions
    • Law of multiple proportions
    • Law of reciprocal proportions
    • Gay Lussac's law of combining volumes

  • Answer:

    The difference between phenol, alcohol and ether lies in their different functional groups.

    Phenol is indicated by a phenyl group and a hydroxyl group as C6H5OH. Other examples - catechol, resorcinol, hydroquinone (ortho, meta and para isomers respectively).

    Alcohol too has a hydroxyl group but not as phenol. It is indicated as R-OH, where R = any alkyl group. Examples - C2H5OH (ethyl alcohol), PhCH2OH (benzyl alcohol) etc.

    Ether is characterized as R-O-R where R = any alkyl group. -O- is the typical ether linkage. Examples - C2H5-O-C2H5 (diethyl ether), PhCH2-O-CH2Ph (dibenzyl ether).

     

     

  • Answer:

    Steam produces more severe burns because the latent heat of vapourisation of steam is more than boiling water.

    This means that steam has more heat energy than boiling water. Latent heat of steam (vapourisation of water) = 2264.7 kJ/kg.

     

  • Question: What is popoff's rule in organic chemistry?

    Posted in: Chemistry | Date: 22/02/2016

    Answer:

    Popoff's rule states that during the oxidation of an unsymmetrical ketone, the cleavage of the C-CO bond is such that the keto group always stays with the smaller alkyl group.

    Example: CH3COCH2CH2CH3 on oxidation gives two carboxylic acids --- CH3COOH and CH3CH2COOH. The keto group remains with the smaller alkyl group which is -CH3 while the -COOH group of the other carboxylic acid comes from the oxidation of -CH2 group of the bigger alkyl chain.  

  • Answer:

    Sublimation is the method of separating naphthalene from common salt. Sublimation involves the conversion of a solid directly into its vapour state without being converted in the liquid state. Naphthalene vapours can be collected after sublimation and the salt remains as residue.

  • Question: What are the factors that affect evaporation?

    Posted in: Chemistry | Date: 22/02/2016

    Answer:

    The following factors affect evaporation -

    1. Temperature - Higher is the temperature, greater is the rate of evaporation.

    2. Wind velocity - Greater is the wind velocity, higher is the rate of evaporation.

    3. Humidity - High humidity lowers the rate of evaporation. E.g. clothes dry very slowly during rainy season.

    4. Surface area of the material - Greater surface area fecilitates evaporation.

    5. Vapor pressure - More vapour pressure on the liquid surface hinders evaporation.

     

  • Question: Which factors affect evaporation?

    Posted in: Chemistry | Date: 23/02/2016

    Answer:

    The following factors affect evaporation -

    1. Temperature - Higher is the temperature, greater is the rate of evaporation.

    2. Wind velocity - Greater is the wind velocity, higher is the rate of evaporation.

    3. Humidity - High humidity lowers the rate of evaporation. E.g. clothes dry very slowly during rainy season.

    4. Surface area of the material - Greater surface area fecilitates evaporation.

    5. Vapor pressure - More vapour pressure on the liquid surface hinders evaporation.

     

  • Question: Why does a desert cooler cool better on a hot dry day?

    Posted in: Chemistry | Date: 23/02/2016

    Answer:

    The desert cooler cools better on a hot dry day because of evaporation which causes cooling effect. During a hot dry day, the temperature is high and humidity is low. This causes the rate of evaporation to be much higher as compared to any other cooler day. As the rate of evaporation increases, cooling effect also increases.

  • Question: What is the numerical value of Avogadro number?

    Posted in: Chemistry | Date: 23/02/2016

    Answer:

    The numerical value of Avogadro number (N) is 6.022 x 10^23

  • Question: What is solution and what are its characteristics?

    Posted in: Chemistry | Date: 23/02/2016

    Answer:

    A solution is a homogeneous mixture of two or more substances. The characteristics of a solution are as follows-

    1. A solution mainly consists of two components - a solute and a solvent. A solute is the one which gets dissolved in        the solvent. E.g. sugar (solute) in water (solvent).

    2. The particles of solute in a solution are of extremely small size  even to be seen by a microscope.

    3. The solute particles cannot be separated from the soloution by any physical means like filtration, centrifugation,             sedimentation etc.

    4. The amount of solute in a given quantity of solution represents its concentration. More solute indicates more                 concentration (concentrate) and less solute indicates dilute solution.

    5. Addition of solute affects the boiling point, freezing point and vapour pressure of solution.

    6. A solution does not allow scattering of light beams through it. 

  • Answer:

    The mass of an atom is determined by protons and neutrons present in the nucleus of an atom. The electrons present in the outer shell (energy levels) do not contribute to the mass of an atom as electrons are very much lighter as compared to protons and neutrons (a proton is 1836 times heavier than an electron). For reference we may note -

    mass of proton = 1.6726 x 10^-27 kg,

    mass of neutron = 1.6750 x 10^-27 kg,

    mass of electron = 9.11 x 10^-31 kg. 

  • Question: What are the differences between weight and mass?

    Posted in: Physics | Date: 25/02/2016

    Answer:

    The differences between mass and weight are as follows - 

    1. Mass is the amount of matter present in a substance while weight is the gravitational force that acts upon the mass.  Thus, weight (W) = mass x gravity (g)

    2. Mass of a substance is same everywhere while weight varies according to the location of the substance.

    3. Mass of a substance can never be zero while weight can be zero for an object where gravitational force is zero, e.g. in space.

    4. Mass is usually measured in kg and g while weight has a unit of Newton.

    5. Mass is a scalar quantity while weight is a vector quantity having both magnitude as well as direction.

  • Question: What is the mass number of an element?

    Posted in: Physics | Date: 25/02/2016

    Answer:

    Mass number (A) of an element = number of protons + number of neutrons (together known as nucleons in the nucleus of an atom).

    For a quick reference,

    number of electrons = number of protons  = atomic number

    number of neutrons = mass number - atomic number

    Example - mass number of Carbon = 12 (no. of protons = 6, no. of neutrons = 6)

                   mass number of Oxygen = 16 (no. of protons = 8, no. of neutrons = 8)

                   mass number of Sodium = 23 (no. of protons = 11, no. of neutrons = 12)

  • Answer:

    Quenching, annealing and tempering, all are the methods of treatment of a metal which are performed to provide the desired characteristics to a metal. Tempering and annealing are the major processes of heat treatment of steel.

    In annealing, steel is heated to very high temperatures and then it is cooled slowly to room temperature. Annealing gives steel its ductility and toghness.

    Tempering involves heating steel below its critical temprature after it is quenched and hardened. Tempering of steel enhances its ductility but decreases hardness.

    Quenching involves quick cooling of steel after being heated. It is a method of hardening and generally produces a harder material. 

  • Question: Why is neoprene considered superior to natural rubber?

    Posted in: Chemistry | Date: 28/02/2016

    Answer:

    Neoprene and natural rubber are both polymers chemically, but neoprene is synthetic while natural rubber is obtained from trees.

    Neoprene is superior as compared to natural rubber because - 

    1. Natural rubber is temperature sensitive - it becomes sticky at high temperature while hard and stiff at low temperature. Neoprene resists to a wide range of temperature changes.

    2. Neoprene is also resistant to some cemicals like few organic solvents, inorganic chemicals, animal fats and oils.

    3. Neoprene provides better resistance to burning.

  • Question: What are metallic minerals?

    Posted in: Chemistry | Date: 28/02/2016

    Answer:

    Metallic minerals are the minerals which contain any metal in their chemical composition. Example - chalcopyrites which is a copper mineral and contains iron-copper suphide in its chemical set up. Other examples include bauxite, tin, manganese, gold etc. 

    Metallic minerals have a shine or lustre of their own because of the matal present in them. Metallic minerals generally originate from igneous rocks and they are malleable and ductile and not brittle.

  • Question: What is inductive effect?

    Posted in: Chemistry | Date: 29/02/2016

    Answer:

    Inductive effect is a charge transfer effect through atoms resulting in bond polarity.

    More elaborately, when two covalently bonded atoms differ in their electronegativities (two unlike atoms), then the bonded electrons are shifted slightly more towards the atom which has a greater electronegativity. This develops a polarity in the bond (bond polarization) resulting in inductive effect.

    Example: 

    δ+        δ-

    CH3 – Cl

    In the above exapmle, the C-Cl bond is a polar covalent bond as the electron is shifted more towards the more electronegative chlorine atom and it thus develops a slight negative charge leaving a slight positive charge in carbon.

    Inductive effect is of two types, the +I and -I effect depending on the nature of electron withdrawing and electron donating effects.

     

  • Answer:

    Haber's process (developed by Fritz Haber and Carl Bosch) is a method of production of ammonia by using atmospheric nitrogen and hydrogen derived mainly from natural gas (methane) under high temperature and pressure conditions in the presence of a metal catlyst. The balanced reaction for Haber's process is given as - 

    N2 (g) + 3H2 (g) -------------->  2NH3 (g)

    Reaction conditions - 

    • ratio of nitrogen and hydrogen = 1:3
    • reaction is exothermic (ΔH = -92.4 kJ/mol)
    • temperature is around 400 - 500 °C
    • pressure is between 150 - 250 atmospheres
    • catalyst - pure iron together with promoter - KOH or K2O, CaO, SiO2 etc.

  • Answer:

    Out of colloids, solution and suspension, solution has particles of smallest size. The size of particles in solution is of the atomic or molecular or ionic level. Particle size ranges between 0.1 to 2 nm (approx.) E.g. sugar and water solution, water and ethanol solution etc.

    Colloids have a particle size ranging between 2 - 1000 nm. E.g. fog, milk etc.

    Suspensions have particle size ranging between 1000 nm to 10-6 m E.g. oil and water, aerosol sprays etc.

  • Answer:

    The name of the days when sun rises exactly east and sets exactly west is EQUINOX.

  • Answer:

    There are several ways of expressing the concentration of a solution, namely - 

    mass percentage, volume percentage, parts per million (ppm), molarity, molality, mole fraction, normality etc.

    Most commonly, the concentration of a solution is expressed as mass or volume percentage and molarity or molality, although molarity is temperature dependent, it is used quite commonly used to express the concentration of a solution.

  • Answer:

    It is easy to test whether a given solution is saturated or not. We just have to keep on adding the same solute to the solvent and if the solute gets dissolved, saturation is not achieved. This means, the solvent has a capacity to hold more solute. As we continue adding the solute to the solvent, a stage comes when the solute can no longer dissolve in the solvent. The solute at this stage can be seen settling at the bottom of the container and not getting dissolved. At this stage the solution is said to completely saturated. 

    We can do a saturation test easily at home using sugar and a glass of water.

  • Question: What is aerosol?

    Posted in: Chemistry | Date: 02/03/2016

    Answer:

    An aerosol is a colloidal system containing solid or liquid particles in air or any other gaseous environment. These may be natural or man-made. Some natural aerosols are - fog, mist, hot water geysers, fumes from forest fires etc. The artificial aerosols include dust, haze, smoke, air pollutants, perfumes, sprays, deodorants etc.

  • Answer:

    When methanal (formaldehyde) reacts with hydrogen cyanide (HCN), it gives rise to a cyanohydrin. It is a classic example of base catalysed nucleophilic addition reaction of aldehydes. The reaction can be shown as -

    H – CHO    +   H – CN -------------> H – CHOH – CN  

    The CN- ion acts as the nucleophile and it adds across the carbonyl group of the aldehyde.

    The product is hydroxymethanenitrile or formaldehyde cyanohydrin.

  • Question: What is mean by the term ‘alloy’?

    Posted in: Chemistry | Date: 02/03/2016

    Answer:

    An alloy is a mixture of two or more metals. Alloying imparts special characters to the metal mixtures making them useful in a variety of applications. Examples of some common alloys are - steel (alloy of iron and carbon), brass (alloy of copper and zinc), bronze (alloy of copper and tin), amalgam (alloy of mercury with any other metal), duralium (alloy of aluminium with copper, manganese, magnesium), 18 - carat gold (alloy of gold with minor quantities of nickel, copper and zinc) etc. 

  • Answer:

    Soap solution should scatter light because the solution is not a homogeneous mixture while sugar solution is a homogneous mixture where the solute particles are evenly distributed and forms a single phase. Soap solution forms a colloidal mixture and it is well known that colloidal particles scatter light (Tyndall effect).

  • Answer:

    Colloidal particle size = 2 - 1000 nm.

    Solution particles size = 0.1 to 2 nm (approx.) (size ranges at the molecular, atomic or ionic level).

    Suspension particle size = 1000 nm to 10-6 m 

    Thus, suspension particles have largest size.

  • Answer:

    Fractional distillation is used to separate a mixture of liquids whose boiling points differ by less than 25 deg C. In fractional distillation, the mixture of liquids is distilled through a fractionating column where the liquid with the lowest boiling point is distilled first and then the next liquid with next higher boiling point and so on with the last liquid to be distilled having the highest boiling point.

    Fractional distillation finds application in the separation of components of crude oil and in the separation of nitrogen and oxygen from liquid air.

  • Answer:

    Sublimation is the best method for separating iodine from common salt (NaCl). Since iodine is sublimable, it will change to vapour state directly from solid when heated slightly and the iodine vapours can be collected while common salt remains as such.

  • Question: What will happen if saturated solution is cooled?

    Posted in: Chemistry | Date: 03/03/2016

    Answer:

    If a saturated solution is cooled below a temperature at which the solution is prepared, then it will lead to a decrease in solubility of the solute. This decrease in solubility will result in some of the dissolved solute to precipitate out as solid crystals which can be easily observed in the container carrying the solution. Again, if this solution is heated, the crystals would dissolve in the solution and no longer be visible.

  • Answer:

    Sublimation is basically a change of state from solid directly to vapour/gas without undergoing the liquid state.

    The mixtures of solid substances with one sublimable material and other non-sublimable material can be separated by sublimation. Examples of sublimable substances- ammonium chloride, camphor, iodine, naphthalene, anthracene etc.

  • Answer:

    Solubility of solids in liquid increases with increase in temperature. Thus, solubility of solids in liquid is directly proportional to temperature.

  • Answer:

    Raw natural rubber is obtained from the sap of rubber tree and it is derived from latex. Vulcanized rubber is obtained by treating natural rubber with sulphur which leads to highly altered properties as compared to natural rubber. The differences between the two are -

    • natural rubber is soft and sticky during summers while vulvanized rubber is hard and non-sticky
    • vulcanized rubber has high tensile strength and resistance to wear and tear than natural rubber
    • vulcanized rubber has a wide temperature range 
    • vulcanized rubber is resistant to most of the chemical solvents

     

  • Answer:

    When a beam of light is passed through a colloidal solution, there is scattering of light by the colloidal particles. This scattering of light by colloidal particles is known as Tyndall effect. Example - A beam of light is scattered by a glass of milk but it passes clean and unscattered through a sugar-water solution.

  • Question: Why should we wear cotton clothes in summer?

    Posted in: Chemistry | Date: 04/03/2016

    Answer:

    We shoud wear cotton clothes in summer because during summers we tend to sweat a lot and cotton fabric absorbs this sweat and helps the body to cool down. Cotton clothes provide better air circulation leading to more absorption of sweat and thus gives a cooling effect to us. 

  • Answer:

    Steam produces more severe burns than boiling water because the LATENT HEAT of steam is greater than water. It means that steam has greater heat energy than boiling water which causes more severe burns.

  • Question: What is the melting point of ice?

    Posted in: Chemistry | Date: 04/03/2016

    Answer:

    The melting point of ice is the same as freezing point of water that is, zero deg. C. The temperature for freezing and melting in case of water is same because it involves a change of phase although in a direction opposite to each other. When water freezes to ice, it releases some energy. The same amount of energy is required to melt it from ice to water. This energy is latent heat which causes phase change without changing temperature.

  • Question: What is 'matter'?

    Posted in: Chemistry | Date: 04/03/2016

    Answer:

    Anything that occupies space and has mass is known as matter. Anything that has a physical existence is matter. We are surrounded by matter.

  • Answer:

    The rate of evaporation is affected by the following factors:

    1. Temperature - Higher the temperature, higher the rate of evaporation

    2. Humidity - Higher the humidity, lower the rate of evaporation

    3. Wind velocity - High wind velocity results in more evaporation

    4. Surface area - more surface area of the material, more evaporation

    5. Vapour pressure - more vapour pressure on the liquid surface, less evaporation 

  • Question: Which substance is used as a filler in rubber objects?

    Posted in: Chemistry | Date: 04/03/2016

    Answer:

    Amorphous silica and carbon black are used mainly as filler materials in rubber items. These provide long-life and strength to sustain wear and tear in rubber objects.

  • Question: What is the full form of CNG?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    CNG is Compressed Natural Gas.

    It is actually methane (natural gas) stored at high pressure and its combustion produces less hazardous gases as compared to petrol, diesel, LPG etc.

  • Question: What is sublimation?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    Sublimation is a change of state in which a substance upon heating transforms from solid directly to vapour/gaseous state without undergoing the liquid state.

    Few sublimable substances - iodine, naphthalene, camphor, anthracene, ammonium chloride etc. 

  • Question: What do you understand by the term ‘latent heat’?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    Latent heat is the amount of heat absorbed or released by a substance during a phase change without undergoing change in temperature. 

    Phase change refers to the change in state, e.g. heat is absorbed when water changes from liquid to vapour state and this is known as latent heat of vapourization.

    Similarly, heat is released when ice (solid) melts to water (liquid), which is known as the latent heat of fusion.

  • Question: What are the characteristics of matter?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    Matter is anything that occupies space and has mass. Every entity that has a physical existence is matter. 

    Matter is characterised by both Physical and Chemical properties.

    1. Physical properties of matter - This is classified into two categories -

    a. Extensive properties - These include mass, volume, length and all physically defined dimensions of matter.

    b. Intensive properties - These include colour, odour, temperature, conductivity, lustre and other qualitative properties.

    2. Chemical properties - These are related to the chemical changes that matter can undergo to generate new substances. These include acidity, basicity, oxidation, reduction, combustion etc.

  • Answer:

    A positron is the antiparticle of electron. It can also be called as a "positive electron" because it resembles electron in all respect except the sign which is positive in positron and negative in electron.Represented as β+ 

    Neutrino on the other hand is a neutral particle (no charge) with such an exceptionally small rest mass that it is ignored. Represented as ν.

  • Question: What is SI unit of temperature?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    Kelvin is the primary unit of temperature (absolute scale). But degree celcius is very commonly used along with kelvin. Adding 273.15 to degree celcius value gives kelvin temperature.

    K =  °C + 273.15 

     

  • Question: Why is light not considered matter?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    Light is not considered matter because, light is just a form of energy. It neither occupies space (no volume), nor does it have any mass, which are the two essential characteristics of matter.

  • Question: What is 'Volatile Liquid'?

    Posted in: Chemistry | Date: 05/03/2016

    Answer:

    The meaning of the term "volatile" is something which can vapourize easily. It is generally applied for liquids. Volatile liquids are those liquids which can easily change to their vapour state at a particular temperature. The liquids with higher vapour pressure are volatile.

    Example: alcohol, acetone, perfumes etc. are volatile at room temperature. 

  • Answer:

    Naturally occuring uranium contains almost 99.3% U - 238 and 0.7% U - 235 which are the two naturally occuring isotopes of uranium. Out of these two isotopes, only U-235 is fissile in nature. This means that only U-235 is capable of undergoing a fission chain reaction (splitting up of the uranium atom) in the nuclear reactor.

    Thus, the naturally occuring uranium needs to be 'enriched' with U-235 isotope. Enrichment means that the percentage of U-235 isotope has to be increased in the naturally occuring uranium ore before it can be used as a nuclear fuel. The process of enrichment is done by isotope separation based on the difference in masses of the two isotopes.

  • Answer:

    Latent heat is the amount of heat which is utilised in changing the phase of a substance, that is from solid to liquid (latent heat of fusion) and from liquid to gas (latent heat of vapourisation). Latent heat does not cause a rise in temeperature of a substance because all heat is utilised for change of phase which takes place by overcoming the forces of interaction between the molecules. 

    In case of phase change from solid to liquid, the intermolecular forces between the solid particles has to be weakened to convert it to liquid and this requires energy which is provided by latent heat. Similarly, during vapourisation, the conversion of liquid to gas also requires energy to overcome intermolecular forces, again provided by latent heat. Thus, there is no rise in temperature.

  • Answer:

    The intermolecular forces of attraction which bind the molecules of solids, liquids and gases are weakest in case of gases. Thus, the gas molecules are far away from each other and free to move in any direction. Hence, gases can acquire any shape and volume unlike liquids in which these intermolecular forces are also weak but stronger than gases which leads to liquids also to acquiring any shape but their volume is fixed.  

  • Answer:

    Chair conformation of cyclohexane is more stable than boat form because in chair conformaion the C-H bonds are equally axial and equatorial, i.e., out of twelve C-H bonds, six are axial and six are equatorial and each carbon has one axial and one equatorial C-H bond. This leads to a staggered conformation in chair form, reducing torsional strain. 

    In boat form, there are eclipsing interactions which enhance torsional strain. In addition to this, the two hydrogens at the top corners of the boat experience steric hindrance (the flagpole hydrogens). This also adds to less stability of boat conformation as compared to chair.

  • Question: What is structural isomerism?

    Posted in: Chemistry | Date: 08/03/2016

    Answer:

    Structural isomerism (constitutional isomerism) is a phenomenon in which two compounds have same molecular formula but they are arranged or bonded differently. This excludes stereoisomers in which the arrangement of atoms is considered in 3-D space. 

    There are several types of structural isomerism -

    1. Chain isomerism, 2. Position isomerism, 3. Functional group isomerism

    Example - butane and 2-methylpropane (chain isomers, same molecular formula C4H10 but differ in arrangement due to branching).

  • Question: What is stereochemistry?

    Posted in: Chemistry | Date: 08/03/2016

    Answer:

    Isomers are basically of two types - constitutional isomers and stereoisomers. Stereoisomers are the molecules which have same molecular formula but they differ in the arrangement of atoms in space. Thus, stereoisomers are spatial isomers (differ in arrangement in 3-D space). They are further classified  into diasteriomers and enantiomers.

    Stereochemistry is a branch of chemistry which is focussed on the study of stereoisomers. Steroisomers are huge in number and thus a special branch is needed to study and classify them and understand their properties.

  • Answer:

    Unsaturated hydrocarbons are mainly identified by two unsaturation tests - 

    1. Bromine water test - If an unsaturated hydrocarbon is added to bromine water, then it decolourises bromine water, that is, the brown colour of bromine water vanishes. This is due to addition of Br2 across multiple bond of unsaturated alkene.

    2. Baeyer's test - When an unsaturated hydrocarbon is added to cold alkaline KMnO4 solution, then there is decolourisation of KMnO4 solution. This is also an addition reaction across multiple bond.

    Saturated hydrocarbons do not give any of the above tests.

  • Question: What is Diels-Alder reaction?

    Posted in: Chemistry | Date: 08/03/2016

    Answer:

    Diels - Alder reaction is a [4+2] cycloaddition reaction between a conjugated diene and a substituted alkene (known as dienophile) which results in the formation of a cyclohexene system. It utilises 4π electrons of the diene and 2π electrons of the dienophile resulting in the formation of new σ bonds.

    This reaction is useful mainly in the synthetic organic chemistry for the formation of 6-membered rings which can be stereochemically controlled.

  • Question: What are the functional groups in phthallic acid?

    Posted in: Chemistry | Date: 08/03/2016

    Answer:

    Phthalic acid is an aromatic dicarboxylic acid. It contains two carboxylic acid groups adjacent to each other on the benzene ring. IUPAC name: benzene-1,2-dicarboxylic acid.

  • Answer:

    The intermolecular forces of attraction in case of solids is strongest and it is weakest in case of gases. Thus, solids have a fixed shape and volume but gases do not have fixed shape and volume. Liquids are intermediate between the two and have fixed volume but not shape. 

    The molecules of solids are very close to each other and no movement is possible between them, thus solids are more compact and dense. In liquids the molecules are not so close and are free to move, thus liquids can flow. In gases the molecules are farthest and free to move anywhere.  

  • Question: What is meant by freezing point?

    Posted in: Chemistry | Date: 09/03/2016

    Answer:

    The temperature at which a substance undergoes a phase change from liquid to solid is known as its freezing point.  

    Example - the freezing point of water is 0 °C.

  • Answer:

    The priority order of organic compounds functional group is -

    [Highest priority]  carboxylic acid (-COOH) > sulphonic acid (SO3H) > ester (-COOR) > acid halide (-COX) > amide (-CONH2) > nitrile (-CN) > aldehyde (-CHO) > ketone (-CO) > alcohol (-OH) > amine (-N-) > ether (-O-), alkene > alkyne [lowest priority]. 

  • Answer:

    E-Z configuration of organic compounds is an extension of cis-trans notation. It describes the absolute stereochemistry of the compound rather than relative stereochemistry as described by cis-trans notation.

    E-Z notation is useful when the carbon atoms of the double bonds have more number of unlike/different substituent attached to them. In this condition it cannot be named by a cis-trans notation, but named according to a priority order (based on Cahn-Ingold-Prelog system) given to each of the substituents.

    Accordingly, when the two high priority groups are on the same side of the double bond, the configuration is z ("Zusammen" = together).

    Similarly, when the two high priority groups are on the opposite side of the double bond, the configuration is E ("Entgegen" = opposite)

     

  • Answer:

    Degree of unsaturation (hydrogen deficiency index) is a useful method in determining the number of double and triple bonds and rings in a molecule. This is useful in predicting the structure of a compound using spectroscopic methods. It is determined using the following formula - 

    degree of unsaturation = n+1 - [(m - t)/2]

    where n = number of tetravalent atoms (carbon) in the compound

    m = number of monovalent atoms (Hydrogen and halogen), t = number of trivalent atoms (Nitrogen, phosphorus)

    oxygen and sulphur are ignored in this calculation.

  • Answer:

    Gravitational force (g). Its value is approximately 9.8 m/s2 on earth.

  • Answer:

    Simple microscope                                                                         Compound microscope

    It uses only a single lens                                                             It uses two lenses – objective and eyepiece

    Its magnification is less, based on only one lens                            Higher magnification as multiplied by eyepiece                                                                                                  and objective lenses

    Its use is limited to simple things as reading small letters etc.        Widespread use as studying the structure of micro                                                                                                    organisms, cells, tissues etc.

  • Answer:

    When methanal (formaldehyde) is reduced in the presence of palladium (catalytic hydrogenation) then we get methanol (an alcohol) as the major product.

                        Pd (catalyst)

    HCHO + H2 -------------------------> CH3OH 

  • Answer:

    Aldehydes and ketones add to HCN to form compounds known as cyanohydrins or hydroxynitriles.

    Similarly when propanone (acetone) adds to HCN, it forms 2-hydroxy-2-methylpropanenitrile or acetone cyanohydrin as -

    CH3COCH3 + HCN ------------------> CH3COHCNCH3

  • Question: What is formalin?

    Posted in: Chemistry | Date: 12/03/2016

    Answer:

    Formalin is a colourless solution of formaldehyde in water, generally used for the preservation of biological specimens.

    Formalin is actually 37% formadehyde solution and an additional 10-15% methanol is also added to prevent polymerisation of formaldehyde. 

  • Answer:

    24-carat gold or pure gold is a soft metal. It is very malleable and ductile but brittle as well. These features makes pure gold susceptible to wear and tear and it is not strong enough to be moulded into various shapes and designs. It easily breaks and thus cannot be used in making ornaments. 

    Thus, pure gold is alloyed with other metals (like copper) (22-carat gold) to provide proper hardness to gold for making ornaments.

  • Answer:

    Metals that are liquids at room temperature are mercury (Hg) and gallium (Ga).

    Non-metals liquid at room temperature - bromine (Br).

    However, other elements such as caesium (Cs), rubidium (Rb) and francium (Fr) also become liquids at a few degrees above room temperature.

  • Question: How are metalloids different from metals?

    Posted in: Chemistry | Date: 13/03/2016

    Answer:

    Metalloids are intermediate between metals and non-metals.

    Metalloids are semi-conductors (like silicon) while metals are good conductors of electricity.

    Metalloids may or may not have lustre, but all metals have lustre (shine)

    Malleability in metalloids is quite less than metals 

    Examples of matalloids - silicon, germanium, arsenic, antimony, tellurium, polonium etc.

    Examples of metals - iron, silver, gold, copper, aluminium, tin etc.

  • Answer:

    1. In roasting, an ore is heated in the presence of excess of air/oxygen while in calcination the ore is heated in the absence/limited supply of oxygen.

    2. Roasting is used for sulphide ores while calcination is used for carbonate ores.

    3. Along with metal oxide SO2 is produced in roasting while CO2 is produced in calcination.

    4. Calcination removes moisture from the ore (dehydrating effect) while roasting has no dehydrating effect.

  • Answer:

    Sulphuric acid is largely used for making phosphoric acid which in turn is used for the manufacture of phosphate fertilizers.

    Thus, fertilizer industry is hugely dependent on sulphuric acid.

  • Answer:

    The name of the organic acid present in vinegar is acetic acid.

    Chemical formula - CH3COOH

  • Answer:

    Carbon monoxide is more harmful and dangerous because it is an extremely toxic, colourless and odourless gas. It is difficult to detect this gas in the environment. It cannot be used by plants unlike CO2 which is utilized by plants for photosynthesis.

    For human beings also it is dangerous because it combines with the haemoglobin of the blood to form a stable compound called oxyhaemoglobin which reduces the oxygen carrying capacity of blood, thus affecting respiration and causing death. CO2 has no such property.

  • Question: What does 'slaking of lime' stand for?

    Posted in: Chemistry | Date: 16/03/2016

    Answer:

    'Slaking of lime' is the conversion of quicklime/lime, which is CaO into Ca(OH)2 or slaked lime by addition of water.

    Quicklime is highly caustic and addition of water makes it less caustic but more alkaline hydrated lime/ slaked lime.

    CaO + H2O -------------> Ca(OH)2 

    quicklime                    slaked lime

     

  • Question: Which functional group present in the compound CH3NH2?

    Posted in: Chemistry | Date: 16/03/2016

    Answer:

    CH3NH2 is methylamine.

    It is the simplest primary amine.

    The functional group is -NH2 (amino group)

  • Answer:

    CH3COONa         +     NaOH ----------------> CH4 + Na2CO3

    sodium ethanoate       soda lime             methane   sodium carbonate

    It is a decarboxylation reaction (loss of carboxyl group, replaced by a hydrogen)

  • Answer:

    When dry blue crystals of copper sulphate are added to conc. H2SO4, then it undergoes dehydration because, H2SO4 is a strong dehydrating agent. Thus, the crystal becomes white from blue as it loses its water of hydration.

    CuSO4.5H2O + H2SO4 --------------------> CuSO4 + 5H2O + H2SO4

    hydrated CuSO4 (blue)                      anhydrous CuSO4 (white)

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