### Gopal J Male, 37 Years

Associated for 6 Years 11 Months
Class 11 - 12 Tutor

#### Activity Score - 881

Location: Bhopal, India
• Total Experience:
13 Years
• Hourly Fees:
INR 400
Tutoring Experience :
I have been teaching Mathematics, Physics, Chemistry to the students of class VI - X of all boards and Mathematics, Chemistry to the students of class XI - XII of all boards since last nine years. I also teach Mechanical subjects to the engineering students of college level. My teaching style is unique it is beneficial for boards as well as competitive examination.
Tutoring Option :
Home Tuition Only
Tutoring Approach :

I approach tutoring in such a way that I show the students the basics, and then give them a variety of practice exercises and urge them figure out the answers themselves. If in doubt, I would keep prompting them to find the right answers thereby helping them to grasp the right concepts. Simple and Basic approach.

Teaches:
 Class 9 - 10 Mathematics Physics Chemistry ICSE CBSE Local State Board IGCSE INR 250 / Hour Class 11 - 12 Mathematics Chemistry All Boards English Medium INR 400 / Hour Engineering Subjects Mechanical INR 500 / Hour Class 6 - 8 Mathematics Physics Chemistry All Boards INR 200 / Hour

### 4 Notes written by me

• #### TRANSITION METALS

Files: 1

Introduction to transition and Inner transition elements, their corresponding properties, oxidation states etc.

• #### Electro Chemistry

Files: 1

This file is introduction to basic terms related with electrochemistry.

• #### MATERIAL SCIENCE (SOLID STATE)

Files: 2

Notes comprise the fundamentals of Solid state (Chemistry) for 12th standard. Another one is key point about metallurgy of steel from iron

• #### Kinetic Theory Of Gases

Files: 1

Fundamental concept regarding kinetic theory of gases comprising: pressure of ideal gas Ideal gas equation Vander waal\'s gas equation Various Speeds of Gas Molecules Kinetic Energy of Ideal Gas Degree of Freedom Law of Equipartition of Energy Specific ...

• ## Question: Why does water have a high boiling and melting point compared to hydrogen sulphi...

Posted in: Chemistry | Date: 22/09/2015

In water molecule electronegative element oxygen is bonded with hydrogen atom by hydogen bonding due to which at room temperature water is in liquid state and also having high B.P. andM.P. rather than hydogen sulphide.

Hydrogen bond is formed when most electronegative elements (F>O>N) directly attached to H-atom.

• ## Question: How does a sodium atom form its cation?

Posted in: Chemistry | Date: 22/09/2015

Sodium is an alkali metal, present in group 1 of periodic table, having low ionisation energy (losing of electron).

Due to low ionisation enthalpy and metalic nature ,it easily loses electron which is present in its outermost orbit (valence cell) and forms Na+ (sodium ion).

• ## Question: Why chloroacetic acid is more acidic than acetic acid ?

Posted in: Chemistry | Date: 22/09/2015

Due to -ve inductive effect of Cl ionisation of chloroacitic increases and its Ka value becomes higher.Hence, chloroacitic acid becomes stronger acid than acitic acid. Ka for ClCH2COOH =1.3 x10^-3 Ka for CH3COOH = 1.8 x1o^-5

• ## Question: What are polypeptides ?

Posted in: Chemistry | Date: 22/09/2015

Polypeptides are chains of amino acids. Proteins are made up of one or more polypeptide molecules.

The amino acids are linked covalently by peptide bonds. The graphic on the right shows how three amino acids are linked by peptide bonds into a tripeptide.

One end of every polypeptide, called the amino terminal or N-terminal, has a free amino group. The other end, with its free carboxyl group, is called the carboxyl terminal or C-terminal.

• ## Question: What role does cryolite play in Hall Heroult process ?

Posted in: Chemistry | Date: 22/09/2015

Elemental aluminium cannot be produced by the electrolysis of an aqueous aluminium salt because hydronium ions readily oxidize elemental aluminium. Although a molten aluminium salt could be used instead, aluminium oxide has a melting point of over 2,000 °C (3,600 °F) so electrolyzing it is impractical. In the Hall–Héroult process alumina, Al2O3, is dissolved in molten cryolite, Na3AlF6, to lower its melting point for easier electrolysis,it also increases conductivity of the solution.

Pure cryolite has a melting point of 1,012 °C (1,854 °F). With a small percentage of alumina dissolved in it, its melting point drops to about 1,000 °C (1,800 °F). Aluminium fluoride, AlF3 is added to the mixture to further reduce the melting point.

• ## Question: What are the two functions of carbohydrates in plants ?

Posted in: Chemistry | Date: 22/09/2015

Functions of carbohydrates in plants.

(i) Cell walls of plants are made up of cellulose, a polysaccharide.

(ii) Carbohydrates are stored in the form of starch (a polysaccharide) as the reserve food material.

• ## Question: What is fehling's test ?

Posted in: Chemistry | Date: 22/09/2015

Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functional groups, and as a test for reducing sugars and non reducing sugars. It is made initially as two separate solutions, known as Fehling's A and Fehling's B. Fehling's A is a blue aqueous solution of copper(II) sulphate, while Fehling's B is a clear and colorless solution of aqueous potassium sodium tartrate (also known as Rochelle salt) and a strong alkali (commonly sodium hydroxide).

• ## Question: What is meant by invert sugar ?

Posted in: Chemistry | Date: 23/09/2015

A mixture of equal parts of glucose and fructose resulting from the hydrolysis of sucrose. It is found naturally in fruits and honey and produced artificially for use in the food industry.

• ## Question: Can you explain Silver-mirror test of aldehydes ?

Posted in: Chemistry | Date: 23/09/2015

Tollens’ test, also known as silver-mirror test, is a qualitative laboratory test used to distinguish between an aldehyde and a ketone.  It exploits the fact that aldehydes are readily oxidized (see oxidation), whereas ketones are not.  Tollens’ test  uses a reagent known as Tollens’ reagent, which is a colorless, basic, aqueous solution containing silver ions coordinated to ammonia [Ag(NH3)2+].

• ## Question: Can you explain Hall-Heroult process of extraction of Al from Aluminium Oxide?

Posted in: Chemistry | Date: 23/09/2015

The process of extracting a metal from its oxide is, in general, referred to as smelting. The Hall-Heroult process is used industrially for Aluminium production. Aluminium cannot be produced by an aqueous electrolytic process because Hydrogen is electrochemically much nobler than Aluminium. The liquid Aluminium is produced by the electrolytic reduction of Alumina (Al2O3) dissolved in an electrolyte (bath) mainly containing Cryolite (Na3AlF6).

The overall chemical reaction can be written as 2 Al2O3 (dissolved) +3C (s) =4 Al (l) +3 CO2 (g)

• ## Question: Can you explain Tyndal effect ?

Posted in: Chemistry | Date: 23/09/2015

The Tyndall Effect is the effect of light scattering in many directions in colloidal dispersion, while showing no light in a true solution. This effect is used to determine whether a mixture is a true solution or a colloid. "To be classified colloidal, a material must have one or more of its dimensions (length, width, or thickness) in the approximate range of 1-1000 nm."

• ## Question: What is emulsion ? Can you explain various types of emulsion ?

Posted in: Chemistry | Date: 24/09/2015

• An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids.
•  In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrette, milk, mayonnaise, and some cutting fluids for metal working.
• The word "emulsion" comes from the Latin word for "to milk", as milk is an emulsion of fat and water, among other components.
• There are two basic types of emulsions: oil-in-water (O/W) and water-in-oil (W/O).

• ## Question: Can you explain the term peptisation ?

Posted in: Chemistry | Date: 24/09/2015

• Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium. In other words it may be defined as a process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte. The electrolyte used in this process is called as peptizing agent.
• Peptization is also used in nanoparticle synthesis to make a large grouping of particles split into many primary particles. This is done by changing the surface properties, applying a charge, or by adding a surfactant.

• ## Question: What is meant by shape selective catalysis ?

Posted in: Chemistry | Date: 24/09/2015

• Shape-selective catalysis is important for synthesis of organic chemicals and for processing of petroleum fractions and fuels.
• The catalytic reaction that depends upon the structure of pores of the catalyst and the size of the reactant and product molecules is called shape/selective catalysis.
• Zeolites are good shape/selective catalysts because of their honeycomb-like structures. Zeolites are aluminosilicates i.e., three dimensional network silicates in which some silicon atoms are replaced by aluminium atoms.

• ## Question: Why adsorption is always exothermic ?

Posted in: Chemistry | Date: 24/09/2015

• Adsorption is always exothermic. This statement can be explained in two ways.

(i) Adsorption leads to a decrease in the residual forces on the surface of the adsorbent. This causes a decrease in the surface energy of the adsorbent. Therefore, adsorption is always exothermic.       (ii) ΔH of adsorption is always negative. When a gas is adsorbed on a solid surface, its movement is restricted leading to a decrease in the entropy of the gas i.e., ΔS is negative. Now for a process to be spontaneous, ΔG should be negative.                      ΔG= ΔH-TΔS           Since ΔSis negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.

• ## Question: What is brownian motion ? On what factors does it depend ?

Posted in: Chemistry | Date: 24/09/2015

Brownian motion, zigzag, irregular motion exhibited by minute particles of matter when suspended in a fluid. The effect has been observed in all types of colloidal suspensions (see colloid)—solid-in-liquid, liquid-in-liquid, gas-in-liquid, solid-in-gas, and liquid-in gas. It is named for the botanist Robert Brown who observed (1827) the movement of plant spores floating in water.

• ## Question: Can you explain Kohlrausch's law of independent migration of ions ?

Posted in: Chemistry | Date: 24/09/2015

KOHLRAUSCH LAW OF INDEPENDENT MIGRATION OF IONS

In 1874, Kohlrausch formulated the law of independent migration of ions based on the experimental data of conductivities of various electrolytes. This law can be stated as follows:

"At infinite dilution, the dissociation of the electrolyte is complete and hence each ion makes definite contribution to the equivalent conductivity of the electrolyte irrespective of the nature of other ions associated with it."

Therefore the limiting equivalent conductivity of an electrolyte is the algebraic sum of limiting equivalent conductivities of its constituent ions.

• ## Question: Why is it not possible to obtain pure ethanol by fractional distillation ?

Posted in: Chemistry | Date: 24/09/2015

• No, because water and ethanol form what is called an azeotrope. In an azeotrope, the ratio of the liquids is such that distillation cannot separate them, but they boil off together.
• It made possible upto an extent but another technique is also needed. Water and ethanol form an azeotrope so by fractionation alone only about 95% ethanol is obtained but the distillate is then treated with calcium oxide to remove the water and redistilled giving 99%+ ethanol.

• ## Question: What is isotonic solution ?

Posted in: Chemistry | Date: 24/09/2015

An isotonic solution refers to two solutions having the same osmotic pressure across a semipermeable membrane. This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side.

• ## Question: What are meant by colligative properties ?

Posted in: Chemistry | Date: 24/09/2015

Colligative properties of solutions are properties that depend upon the concentration of solute molecules or ions, but not upon the identity of the solute. Colligative properties include freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure.

• ## Question: Can you define Henry's Law ?

Posted in: Chemistry | Date: 24/09/2015

• Henry's law is one of the gas laws formulated by the English chemist William Henry,
• "water takes up, of gas condensed by one, two, or more additional atmospheres, a quantity which, ordinarily compressed, would be equal to twice, thrice, &c. the volume absorbed under the common pressure of the atmosphere."
• In other words, the amount of dissolved gas is proportional to its partial pressure in the gas phase. The proportionality factor is called the Henry's law constant.

• ## Question: Why is the vapour pressure of an aqueous solution of glucose lower than that of ...

Posted in: Chemistry | Date: 24/09/2015

• If a nonvolatile solute such as glucose is added, some fraction of the surface area is occupied by solvated solute molecules.
• As a result, the rate at which water molecules evaporate is decreased, although initially their rate of condensation is unchanged.
• When the glucose solution reaches equilibrium, the concentration of water molecules in the vapor phase, and hence the vapor pressure, is less than that of pure water.

• ## Question: What is denaturation ? What is the biological effect of denaturation of proteins...

Posted in: Chemistry | Date: 28/09/2015

• Denaturation,  in biology, process modifying the molecular structure of a protein. Denaturation involves the breaking of many of the weak linkages, or bonds (e.g., hydrogen bonds), within a protein molecule that are responsible for the highly ordered structure of the protein in its natural (native) state. Denatured proteins have a looser, more random structure; most are insoluble. Denaturation can be brought about in various ways—e.g., by heating, by treatment with alkali, acid, urea, or detergents, and by vigorous shaking.
• Denaturation causes loss in biological activity of the protein. It does not change the primary structure of the protein but results from rearrangement of secondary and tertiary structures

• ## Question: What are the products of complete hydrolysis of Xenon Hexafluoride ?

Posted in: Chemistry | Date: 28/09/2015

Xenon hexafluoride is a noble gas compound with the formula XeF6 and the highest of the three known binary fluorides of xenon, the other two being XeF2 and XeF4. All known are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinating agent of the series. At room temperature, it is a colorless solid that readily sublimes into intensely yellow vapors.

Xenon hexafluoride hydrolyzes stepwise, ultimately affording xenon trioxide:[6]

XeF6 + H2O → XeOF4 + 2 HF

XeOF4 + H2O → XeO2F2 + 2 HF

XeO2F2 + H2O → XeO3 + 2 HF

XeF6 serves as a Lewis acid, binding one and two fluoride anions:

XeF6 + F^- → XeF7^-

XeF7?^- + F− → XeF2−

• ## Question: Can you explain BOP method of steel making ?

Posted in: Chemistry | Date: 28/09/2015

• Basic oxygen steelmaking (BOS, BOP, BOF, and OSM), also known as Linz-Donawitz-Verfahren steelmaking or the oxygen converter process is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into low-carbon steel. The process is known as basic because fluxes of burnt lime or dolomite, which are chemical bases, are added to promote the removal of impurities and protect the lining of the converter.
• The Basic Oxygen Steelmaking process differs from the EAF in that it is autogenous, or self-sufficient in energy. The primary raw materials for the BOP are 70-80% liquid hot metal from the blast furnace and the balance is steel scrap. These are charged into the Basic Oxygen Furnace (BOF) vessel. Oxygen (>99.5% pure) is "blown" into the BOF at supersonic velocities. It oxidizes the carbon and silicon contained in the hot metal liberating great quantities of heat which melts the scrap. There are lesser energy contributions from the oxidation of iron, manganese, and phosphorus. The post combustion of carbon monoxide as it exits the vessel also transmits heat back to the bath.
• The product of the BOS is molten steel with a specified chemical anlaysis at 2900°F-3000°F. From here it may undergo further refining in a secondary refining process or be sent directly to the continuous caster where it is solidified into semifinished shapes: blooms, billets, or slabs.
• Basic refers to the magnesia (MgO) refractory lining which wears through contact with hot, basic slags. These slags are required to remove phosphorus and sulfur from the molten charge.

• ## Question: How is pig iron converted into steel ?

Posted in: Chemistry | Date: 28/09/2015

• The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron prior to the open hearth furnace. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron. The oxidation also raises the temperature of the iron mass and keeps it molten.
• The process is carried on in a large container called the Bessemer converter, which is made of steel and has a lining of silica and clay or of dolomite. The capacity is from 8 to 30 tons of molten iron; the usual charge is 15 or 18 tons. The converter is egg-shaped. At its narrow upper end it has an opening through which the iron to be treated is introduced and the finished product is poured out. The wide end, or bottom, has a number of perforations (tuyeres) through which the air is forced upward into the converter during operation. The container is set on pivots (trunnions) so that it can be tilted at an angle to receive the charge, turned upright during the "blow," and inclined for pouring the molten steel after the operation is complete. As the air passes upward through the molten pig iron, impurities such as silicon, manganese, and carbon unite with the oxygen in the air to form oxides; the carbon monoxide burns off with a blue flame and the other impurities form slag. Dolomite is used as the converter lining when the phosphorus content is high; the process is then called basic Bessemer. The silica and clay lining is used in the acid Bessemer, in which phosphorus is not removed. In order to provide the elements necessary to give the steel the desired properties, another substance (often spiegeleisen, an iron-carbon-manganese alloy) is usually added to the molten metal after the oxidation is completed. The converter is then emptied into ladles from which the steel is poured into molds; the slag is left behind. The whole process is completed in 15 to 20 min.

• ## Question: What are carbon nanotubes ?

Posted in: Chemistry | Date: 29/09/2015

Carbon nanotubes (CNTs) are tubular cylinders of carbon atoms that have extraordinary mechanical, electrical, thermal, optical and chemical properties At the individual tube level, these unique structures exhibit: 200X the strength and 5X the elasticity of steel; 5X the electrical conductivity ("ballistic transport"), 15X the thermal conductivity and 1,000X the current capacity of copper; at almost half the density of aluminum. As a carbon based product, CNTs have almost none of of environmental or physical degradation issues common to metals—thermal expansion and contraction, corrosion and sensitivity to radiation—all of which result in greater system failure in performance-sensitive applications in aerospace and defense, aviation, automotive, energy and consumer products.

• ## Question: What do you mean by homogeneous mixture ?

Posted in: Chemistry | Date: 29/09/2015

A mixture which has uniform composition and properties throughout. For example, air is a homogeneous mixture of gases. A teaspoonful of table salt stirred into a glass of water also makes a homogeneous mixture.

• ## Question: What is solubility ?

Posted in: Chemistry | Date: 29/09/2015

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a solution of the solute in the solvent. The solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure and the pH of the solution. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute.

• ## Question: What is a saturated solution ?

Posted in: Chemistry | Date: 29/09/2015

The term saturated solution is used in chemistry to define a solution in which no more solvent can be dissolved. It is understood that saturation of the solution has been achieved when any additional substance that is added results in a solid precipitate or is let off as a gas.

• ## Question: Can you define molarity ?

Posted in: Chemistry | Date: 29/09/2015

Molar concentration, also called molarity,molarity is most commonly expressed in units of moles of solute per litre of solution. For use in broader applications, it is defined as amount of solute per unit volume of solution, or per unit volume available to the species.

• ## Question: How does washing soda remove hardness of water?

Posted in: Chemistry | Date: 29/09/2015

Hard water can be softened by adding washing soda (sodium carbonate) which removes the calcium ions in a precipitation reaction. Alternatively, the hard water can be passed through an ion-exchange resin in a column. Sodium ions replace the calcium ions in the water as it passes through the column.

• ## Question: Why does ice float on water?

Posted in: Chemistry | Date: 29/09/2015

As water is cooled down, however, the molecules have less energy and hydrogen bonding takes over. The molecules form a ordered crystal through hydrogen bonding that spaces the molecules farther apart than when they were in a liquid. This makes ice less dense than water allowing it to float.

• ## Question: Explain the following factors affecting the rate of corrosion.

Posted in: Chemistry | Date: 29/09/2015

Four elements need to be present for corrosion to occur and collectively referred to as the corrosion cell: an anode (+), a cathode (-), a metallic conductor and an electrolyte. Changing the potency of the electrolyte affects the rate of corrosion. Corrosion rates are determined by a variety of factors; however, five factors do play an overwhelmingly important role in determining corrosion rates.

• Oxygen: Like water, oxygen increases the rate of corrosion. Corrosion can take place in an oxygen-deficient environment, but the rate of the corrosion reaction (and destruction of the metal) is generally much slower. In immersed conditions, if an electrolyte is in contact with one area of metal containing more oxygen than the electrolyte in contact with another area of the metal, the higher oxygen-concentration area is cathodic relative to the remaining surface. An oxygen concentration cell then forms, which results in rapid corrosion.
• Temperature: Corrosion reactions are electrochemical in nature and usually accelerate d with increasing temperature; therefore, corrosion proceeds faster in warmer environments than in cooler ones.
• Chemical Salts: Chemical salts increase the rate of corrosion by increasing the efficiency (conductivity) of the electrolyte. The most common chemical salt is sodium chloride, a major element of seawater. Sodium chloride deposited on atmospherically exposed surfaces also acts as a hygroscopic material (i.e., it extracts moisture from the air), which then increases the corrosion in non-immersed areas.
• Humidity: Humidity and time-of-wetness play a large role in promoting and accelerating corrosion rates. Time-of-wetness refers to the length of time an atmospherically exposed substrate has sufficient moisture to support the corrosion process. The wetter the environment, the more corrosion is likely to occur.
• Pollutants: Acid rain (a chemical by-product from manufacturing and processing plants), and chlorides (in coastal areas) promote corrosion. Acid gases, such as carbon dioxide, can also dissolve in a film of moisture in contact with the metal.

• ## Question: Explain the differential metal and stress corrosions.

Posted in: Chemistry | Date: 29/09/2015

1. Galvanic corrosion or differential metal corrosion:

It occurs when two dissimilar metals (galvanic couples) are in contact with each other in a corrosive conductive medium; a potential difference is set up resulting in a galvanic current. The two metals differ in their tendencies to undergo oxidation. The metal with lower electrode potential or more active metal acts as anode and the metal with higher electrode potential acts as cathode. The potential difference is main factor for corrosion to take place. The anodic metal undergoes corrosion where as cathodic metal gets unaffected.

Egs: When iron is in contact with copper, iron has lower electrode potential acts as anode and  undergo oxidation as, Fe

Copper having higher electrode potential acts as cathode & is unaffected. Depending on the corrosive environment near the cathode either hydrogen evolved or oxygen absorbed resulting in hydroxide ion formation.

2. Stress corrosion

The stress on the metal may be internal or external and the stress is due to some mechanical or service conditions. The metal atoms under stress are always at higher energy level so acts as anode and stress free parts of metal acts as cathode under specific corrosive environmental conditions corrosion process starts.

Egs: The best example for stress corrosion is caustic embrittlement.

• ## Question: What is reformation of petrol? Write the reactions involved in it.

Posted in: Chemistry | Date: 29/09/2015

Catalytic reforming is a chemical process used to convert petroleum refinery naphthas distilled from crude oil (typically having low octane ratings) into high-octane liquid products called reformates, which are premium blending stocks for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.

• ## Question: How does water get polluted?

Posted in: Chemistry | Date: 29/09/2015

Atmospheric deposition is the pollution of water bodies caused by air pollution. Each time the air is polluted with sulphur dioxide and nitrogen oxide, they mix with water particles in the air and form a toxic substance. This falls as acid rain to the ground, and gets washed into water bodies.

• ## Question: Which isotope of uranium can undergo fission readily.

Posted in: Chemistry | Date: 28/10/2015

U235 is the fissionable isotope of Uranium. Natural Uranium contains only about 0.7 percent U235, which is enough to produce fission only with a good moderator such as graphite or heavy water. In light water reactors the Uranium has to be enriched to about 4 percent U 235. Also the artifficial isotope 233U.

• ## Question: How are metals low in activity series extracted from their ores?

Posted in: Chemistry | Date: 28/10/2015

Metals that are low in the activity series are very un-reactive. The oxides of these metals can be reduced to metals by heating alone. For example, mercury is obtained from its ore, cinnabar (HgS), by the process of heating.

Copper can also be obtained in a similar manner from its sulphide ore (Cu2S).

• ## Question: Why does milk turns sour if kept outside for a long time?

Posted in: Chemistry | Date: 28/10/2015

Like many other things, milk contains bacteria, the tiny little critters that live naturally in and on lots of things and are so small you can only see them if you use a microscope. Milk also naturally contains a kind of sugar known as “lactose.” The bacteria that live in milk get energy from this special sugar and use it to reproduce to make even more bacteria!

When the bacteria use the lactose sugars to reproduce, they change it from “lactose sugar” into “lactose acid,” which tastes sour. When this happens, the milk curdles and is no longer the smooth, tasty liquid that you're used to drinking!

• ## Question: Give one example of zero order reaction.

Posted in: Chemistry | Date: 21/11/2015

All photochemical reactions are zero order reaction.

For example,

Chlorination of alkanes in presence of sun light

Photosynthesis

Write a Review

### Afsar Rza

Amazing explaining capacity. He is also very calm and cooperative.

Gopal sir is ana amazing teacher. He explains very well.

### Ravendra Dwivedi

I took classes for Engineering Mechanics. He has a unique style of teaching.

### Md Shoaib

I am taking classes from Gopal Sir for Mechanical Engineering subjects. He teaches really well. He is a great teacher.

Gopal sir is the best teacher for Chemistry & Mathematics. I have taken classes for two years. His way of teaching is very good.

### Prashant Kumar Bajpayee

I am taking Chemistry tuition from Sir for more than two years. He teaches very well. He is a very good teacher.

### Rajiv Pandey

My daughter took Chemistry and Physics tuition from Gopal Sir for more than Six months. He is a very sincere teacher and has a great knowledge. My daughter has improved a lot in her results.

Sir taught me Chemistry and Mathematics for more than two months. He has a vast knowledge in this field. I have improved a lot.

### Pakhi Shrivastav

I took Chemistry and Mathematics tuition from Sir. He is a very nice teacher. He is very friendly and gives proper attention to each and every student.

### Mubeen Khan

As a teacher, he is very nice. He teaches very well and explains well.

### Ravi Malviya

I took Physics, Chemistry and Mathematics tuition from Sir for more than two years. He is a great teacher. Highly knowledgeable.

### Mukesh Mishra

He taught my son Chemistry for more than a year. He is a nice teacher. He has a unique style of teaching.

### Krishna Kumar

He is a very good teacher. I took tuition for four years . He explains very well and as a teacher he is excellent. He has a unique way teaching.

My daughter took tuition from him for a year. She took tuition for all subjects while she was in her 11th standard. He is a very good tutor and extremely dilligent.