Chemical Reaction And Equation Previous Year Questions
Chemical Reaction And Equation Previous Year Questions
2020
1. Identify ‘x’, ‘y’ and ‘z’ in the following reaction :
2 KClO3 (x) ---(y)---- 2 KCl (x) + O2(z)
(a) x = gas ; y = reaction condition, z = gas
(b) x = solid ; y = liquid; z = gas
(c) x = number of moles of KClO3 ; y = reaction condition; z = no. of molecules of oxygen.
(d) x = physical state of KClO3 and KCl; y = reaction condition; z = physical state of O2.
2.A compound ‘A’ is used in the manufacture of cement. When dissolved in water, it evolves a large amount of heat and forms compound ‘B’.
(i) Identify A and B.
(ii) Write chemical equation for the reaction of A with water.
(iii) List two types of reaction in which this reaction may be classified.
3.Mention with reason the colour changes observed when :
(i) silver chloride is exposed to sunlight.
(ii) copper powder is strongly heated in the presence of oxygen.
(iii) a piece of zinc is dropped in copper sulphate solution.
4.In which of the following, the identity of initial substance remains unchanged ?
(a) Curdling of milk
(b) Formation of crystals by process of crystallisation
(c) Fermentation of grapes
(d) Digestion of food
5.Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Assertion (A) : Following is a balanced chemical equation for the action
of steam on iron :
3Fe + 4H2O ------ Fe3O4 + 4H2
Reason (R) : The law of conservation of mass holds good for a chemical
equation.
6.Lead nitrate solution is added to a test tube containing potassium iodide solution.
(a) Write the name and colour of the compound precipitated.
(b) Write the balanced chemical equation for the reaction involved.
(c) Name the type of this reaction justifying your answer.
7.What happens when food materials containing fats and oils are left for a long time ? List two observable changes and suggest three ways by which this phenomenon can be prevented.
8.Strong heating of ferrous sulphate leads to the formation of a brown solid and two gases. This reaction can be categorised as
(A) displacement and redox.
(B) decomposition and redox.
(C) displacement and endothermic.
(D) decomposition and exothermic.
9.A shining metal ‘M’, on burning gives a dazzling white flame and changes to a white powder ‘N’.
(a) Identify ‘M’ and ‘N’.
(b) Represent the above reaction in the form of a balanced chemical equation.
(c) Does ‘M’ undergo oxidation or reduction in this reaction ? Justify.
10.In the electrolysis of water
(a) Name the gases liberated at anode and cathode.
(b) Why is it that the volume of gas collected on one electrode is two times that on the other electrode ?
(c) What would happen if dil. H2SO4 is not added to water
