35. What happens when sodium sulphate and barium chloride solutions are mixed together ? Write reaction with

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.

Due to paucity of time it would not be possible for us to provide the answers to all your queries. We are providing solutions to some your good queries. Try solving rest of the questions yourself and if you face any difficulty then do get back to us.

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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