1. Write observation for the following reaction : Granulated zinc reacts with dil. sulphuric acid 2. (a) Identify the substance oxidized, substance reduced, oxidizing agent and reducing agent in the following reaction : ZnO + C = Zn + CO 3. Balance the following chemical equation : FeSO4 (s) .Fe2O3 (s).+ SO2 (g).+ .SO3 (g) 4. A light sensitive compound „X. of silver is used in black and white photography. On exposure to sunlight its colour changes to gray : (a) Identify „X. (b) Write a chemical equation to express the above change (c) Identify the type of chemical reaction. 5. A white compound on heating decomposes to give brown fumes and a yellow residue is left behind. Name the compound. Write the chemical equation of the reaction stating its type. 6. A brown substance „X. on heating in air forms a substance „Y.. When hydrogen gas is passed over heated „Y., it again changes back into „X.. (i) Name the substance X and Y. (ii) Name the type of chemical reactions occurring during both the changes. (iii) Write the chemical equations of the reactions. 7. Balance the following chemical equation. Fe + H2O . Fe3O4 + H2 8.Write the chemical equation for reactions that takes place when lead nitrate and potassium iodide solutions are mixed. 9. What is meant by a skeletal chemical equation ? Using suitable chemical reaction, differentiate between a skeletal chemical equation and balanced chemical equation. 10. A green coloured hydrated metallic salt on heating loses its water of crystallisation and gives the smell of burning sulphur. Identify the salt and write down the reaction involved. 11. Name the type of following reaction : N2+ 3H2= 2NH3 12. (a) What is corrosion ? Name the compound formed when : (i) silver corrodes (ii) copper corrodes : 13. What happens when quicklime is added to water ? 14. What do you observe when a magnesium ribbon is burnt in air ? Is magnesium oxidised or reduced in this reaction ? Justify your answer 15. Balance the following chemical equation. MnO2(s).HCl(aq). MnCl2(aq)+H2O(l)+Cl2(g) . . 16. Name and state the law which is kept in mind while we balance a chemical equation . 17. Write observation with chemical equation for the following reaction : Carbon dioxide is made to pass through lime water. 18. Explain why : All decomposition reactions are endothermic reactions. 19. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction. 20. A water insoluble calcium compound (A) on reacting with dil. H2SO4 released a colourless and odourless gas (B) with brisk effervescence. When gas (B) is passed through lime water, lime water turns milky and again formed compound A. Identify A and B and write the chemical equations for the reactions involved. 21. State one basic difference between a physical change and a chemical change. 22. Using a suitable chemical equation justify that some chemical reactions are determined by : (i) change in colour, (ii) change in temperature. 23. a) Classify the following reactions into different types (i) AgNO3 (aq)+ NaCl(aq) AgCl(s)+NaNO3(aq) (ii) CaO(s)+H2O. Ca(OH)2 (iii) 2KClO3 (s). 2KCl+ 3O2 (b) Which of the above reaction(s) is/are precipitation 24. Write balanced equations for the following mentioning the type of reaction involved. (i) Aluminium + Bromine ® Aluminium bromide (ii) Calcium Carbonate ® Calcium Oxide + Carbon dioxide (iii) Silver Chloride ® Silver + .Chlorine 25. Consider the above mentioned two chemical equations with two different kinds of arrows along with product. What do these two different arrows indicate ? i) AgNO3 + NaCl . AgCl. +NaNO3 ii) FeS +H2SO4 . FeSO4+H2S . 26. A solution of substance ‘X’ is used for white washing. What is the substance ‘X’ ? 27. Identify the substance that is oxidised and reduced in the reaction : CuO(s) + Zn(s) . Cu(s) + ZnO(s) 28. Write the balanced equation for the following reaction and identify the type of reaction in each case. i) Potassium bromide + Barium Iodide ® Potassium iodide + Barium bromide. ii) Hydrogen (g) + Chlorine(g) ® Hydrogen Chloride (g) 29. What is meant by (i) precipitation reaction. (ii) exothermic reaction. (iii) oxidation reaction. Write balanced chemical equations for an example of each. 30. A zinc plate was put into a solution of copper sulphate kept in a glass container. It was found that blue colour of the solution gets fader and fader with the passage of time. After few days when zinc plate was taken out of the solution, a number of holes were observed on it. (i) State the reason for changes observed on the zinc plate. (ii) Write the chemical equation for the reaction involved 31. A student dropped few pieces of marble in dilute HCl contained in a test tube. The evolved gas was passed through lime water. (i) What change would be observed in lime water ? (ii) Write balanced chemical equation for the above change. 32. You might have noted that when copper powder is heated in a china dish, the surface of copper powder becomes coated with a black colour substance. (i) How has this black coloured substance formed ? (ii) What is that black substance. (iii) Write the chemical equation of the reaction that takes place. 33.Name 2 salts that are used in black and white photography. 34. Is burning of a candle wax a physical change or a chemical change ? 35. What happens when sodium sulphate and barium chloride solutions are mixed together ? Write reaction with observation. 36. An aluminium can is used to store ferrous sulphate solution. It is observed that in a few days holes appeared in the can. Explain the cause for this observation and write chemical equation to support your answer. 37. Why is photosynthesis considered an endothermic reaction ? 38. A few drops of sulphuric acid are added into water before electrolysis. Why ? 39. Balance the following chemical equations : (i) BaCl2 +H2SO4BaSO4+HCl (ii) Ca(OH)2+HNO3Ca(NO3)2+H2O (iii) Pb(NO3)2 PbO+NO2+O2 (iv) MnO2+HClMnCl2+H2O+Cl2 40. State the chemical change that takes place when lime stone is heated strongly. 41. An element ‘X’ on reaction with dilute acid evolves a gas that burns with a pop sound, while a compound ‘Y’ on reaction with dilute acid evolves a gas that turns lime water milky. Identify X and Y. 42. A copper coin was kept dipped in AgNO3 solution for few hours, as shown in the figure. What will happen to the : (a) copper coin’ (b) colour of the solution ? 43. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction ? 44. A white salt on heating decomposes to give brown fumes and a residue is left behind. (i) Name the salt. (ii) Write the equation for the decomposition reaction. 45. Which one is a chemical change-rusting of iron or melting of iron ? 46. Why do silver articles become black after some time when exposed to air? 47. (a) If an iron nail is immersed in the aqueous solution of copper sulphate, what are the changes happening to the nail and to the solution? (b) Write the balanced chemical equation for the reaction between iron metal and aqueous copper sulphate solution. 48. Give an example each for thermal decomposition and photo chemical decomposition reactions. Write relevant balanced chemical equations also. 49. (a) Oil and fat containing food items are flushed with nitrogen while packing them why ? (b) Why do we apply paint on iron articles ? 50. What would you observe when. (i) calcium oxide is added to water ? (ii) barium chloride solution is added to sodium sulphate solution ? Write the reaction involved in each case.

You are not supposed to ask so many questions in a single query. Ask each question separately.

I am answering your 15th and 20th question.

15. The balanced equation is:

MnO2 (s) + 4HCl (aq) ==> MnCl2 (aq) + 2H2O (l) + Cl2 (g)

20. The water insoluble substance (A) is calcium carbonate CaCO3. On reacting with dilute H2SO4 released a colourless and odourless gas accompanied by a brisk effervescence which is carbon dioxide (B).

CaCO3 (s) + H2SO4 (aq) ---------> CaSO4(aq) + H2O (aq) + CO2 (g)

  (A)   (B) 

On bubbling the CO2 gas (B) through lime water (calcium hydroxide) the solution became milky and again forms compound (A) i.e calcium carbonate.

Ca(OH)2 + CO2 (g)----------------->CaCO3 (s) + H2O (l)

   (B)  (A) (milky)

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A-16) Law of Conservation of Mass is a main law to be kept in mind while balancing equations


which states mass neither can be destroyed nor created.It means no of atoms of each element on left hand side should be equal to the no of atoms of each element on right hand side.

A-17) when carbon dioxide is passed through lime water, a white precipitate of calcium carbonate is formed.

If excess CO2 is added, the following reaction takes place:

CaCO3 + H2O + CO2 Ca (HCO3)2


The product formed Ca (HCO3)2 is colorless and is soluble in the solution.

A- 18) 

Decomposition reactions are endothermic in nature. Even if any heat is released, the heat required is much more. So, any ways it comes out to be endothermic.


Reaction: KCl + AgNO3 --> KNO3 + AgCl

Type: Double Displacement Reaction


A-33) Silver bromide and silver chloride are used in black and white photography.

A-34) Burning of a candle is both a physical and a chemical change. Candle is made up of a solid block of wax with a wick embedded in it.

1) Physical Change

When candle is lit, the heat of the flame melts the solid wax to liquid wax. This signifies a physical change from solid state to liquid state.

2) Chemical Change

The wax acts as a fuel when we light the candle and is basically carbon. The carbon combines with oxygen to form another chemical substance which is carbon dioxide. Also the unburnt carbon is deposited as black substance called soot. This signifies a chemical change.

A-35) When solutions of barium chloride and sodium sulphate are mixed together, then an insoluble precipitate of barium sulphate and solution of sodium chloride is obtained. Hence, this reaction is a precipitation (a kind of double displacement reaction) reaction. The chemical equation for reaction between barium chloride and sodium sulphate is represented as follows

BaCl2 + Na2SO4 → BaSO4 + 2NaCl

A-38) Pure water is very weakly ionised and hence does not conduct electricity very well. Sulphuric acid basically increases the conductivity of water, and thereby speeds up the process of electrolysis. However it does not affect the chemical composition of the reactant or products, it only increases the speed of the reaction. Thus it plays the role of a catalyst.

A-44) The said compound is lead nitrate. It is white in colour. When lead nitrate is heated, it decomposes to give lead oxide, nitrogen dioxide and oxygen. Nitrogen dioxide is a brown coloured gas. The chemical equation involved in the reaction is :


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1. Zn+ H2SO4= ZnSO4+ H2

2. Zn oxidised C is reduced

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