PREVIOUS YEAR QUESTIONS
CHEMICAL REACTIONS AND EQUATIONS
1.
What happens chemically when quicklime is added to water filled in a bucket?
2.
Write balanced chemical equations for the following reactions :
(a) Silver bromide on exposure to sunlight decomposes into silver and bromine.
(b) Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.
3.
Identify the type of reaction from the following equations :
(a) CH4 + 2O2 CO2 + 2H2O
(b) Pb(NO3)2 + 2KI PbI2 + 2KNO3
(c) CaO + H2O Ca(OH)2
(d) CuSo4 + Zn ZnSO4 + Cu
4.
Write balanced equations for the reactions between Magnesium and hydrochloric acid. Name the
product obtained, identify the type of reaction.
5.
Describe an activity to observe what happens when quick lime is added to water taken in a beaker.
State two important observation and name the type of reaction taking place.
6.
(a) What is the colour of ferrous sulphate crystals? How does this colour change after heating?
(b) Name the products formed on strongly heating ferrous sulphate crystals. What type of chemical
reaction occurs in this change?
7.
Using balanced chemical equation explain the difference between a displacement reaction and a
double displacement reaction.
8.
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.
(a) State the reason for changes observed on the zinc plate.
(b) Write the chemical equations for the reactions involved.
9.
When the powder of a common metal is heated in an open china dish, its colour turns black.
However, when hydrogen is passed over the hot black substance so formed, it regains its original
colour. Based on the above information answer the following questions:
(a) What type of chemical reaction takes place in each of the two given steps?
(b) Name the metal initially taken in the powder form. Write balanced chemical equations for both
reactions.
10.
A reddish brown coloured metal, used in electrical wires, when powdered and heated strongly in
an open china dish, its colour turns black. When hydrogen gas is passed over this black substance,
it regains its original colour. Based on the above information answer the following questions. (i)
Name the metal and the black coloured substance formed. (ii) Write balanced chemical equations
for both the reactions.
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11.
Write balanced chemical equation for the reactions that take place during respiration. Identify the
type of combination reaction that takes place during this process and justify the name. Give one
more example of this type of reaction.
12.
What is redox reaction? Identify the substance oxidised and the substance reduced in the following
reactions:
(a) 2PbO + C Pb + CO2
(b) MnO2 + 4HCI MnCI2 + 2H2O + CI2
13.
2 g of lead nitrate powder is taken in a boiling tube. The boiling tube is heated over a flame. Now
answer the following:
(a) State the colour of the fumes evolved and the residue left.
(b) Name the type of chemical reaction that has taken place stating its balanced chemical equation.
14.
What is meant by:
(a) displacement reaction
(b) Reduction reaction
(c) Combination reaction.
Write balanced chemical equation for each reaction:
15.
Identify the type of chemical reaction taking place in each of the following :
(a) Barium chloride solution is mixed with copper sulphate solution and a white precipitate is
observed.
(b) On heating copper powder in air in a China dish, the surface of copper powder turns black.
(c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a
gas having odour of burning sulphur is experienced.
(d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the
blue colour of copper sulphate fades away.
(e) Quicklime reacts vigorously with water releasing a large amount of heat.
16.
Write he balanced chemical equations for the following reactions and identify the type of reaction
in each case.
(a) Thermite reactions, iron (III) oxide reacts with aluminium and gives molten iron and aluminium
oxide.
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride
solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
17.
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?
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