Question

precipitate,
during -
EXERCISE
Chemical Reactions
1. State what is a chemical reaction. A chemical reaction is often accompanied by External
indications or characteristics which include a] Colour change bl Effervescence
or gas evolved c) Evolution or absorption of heat dj Formation of a
With reference to each of the above indications, state the external indication segn
1 Addition of dilute acid to an active metal i] Addition of dilute hydrochloric acid to silva
nitrate iii] Addition of water to quicklime iv] Thermal decomposition of mercury (U) olide
2. State why a direct combination reaction is called a - 'synthesis reaction'.
3. Differentiate between a) Direct combination reaction & a decomposition reaction
b) Displacement reaction & a neutralization reaction
4. Classify the following reactions into a) Direct combination
b] Decomposition
c) Displacement d] Double decomposition The reactions are -
il Zinc hydroside on
heating gives zinc oxide & water ii] Zinc reacts with copper (D) sulphate to give zinc sulphate &
copper ii) Zinc sulphate reacts with ammonium hydroxide to give armonium sulphate &
zinc hydroxide iv) Molten zinc at high temperatures, burns in air to give zinc oxide.
5. Give balanced equations for - 1] A direct combination reaction involving two elements, one
of which is a non-metal ii] A thermal decomposition reaction involving heat on limestone
(calcium carbonate) iii] An electrolytic decomposition reaction involving a neutral liquid
iv) A displacement reaction involving a metal above hydrogen in the activity series with
copper (IT) sulphate solution v] A double decomposition neutralization reaction involving
an acid & a base vi] A white precipitate obtained during a double decomposition reaction
involving a silver salt with a sodium salt.
6. State what is meant by 'reactivity series of metals. With reference to a) Water b] Acids
explain with suitable examples how the reactivity of the metals could be differentiated.
7. A chemical reaction may be 'reversible' in nature. State the meaning of the term in italics.
Give a reason why a catalyst is used in certain chemical reactions. Give a balanced equation
for the following - a) A reversible catalytic reaction involving -
1) nitrogen as one of the reactants ii) sulphur dioxide as one of the reactants.
8. State whích type of chemical reactions proceed with - a] Evolution of heat energy
b) Absorption of heat energy. State in each of the following reactions whether heat is evolved
or absorbed 1) water is added to quicklime ii] two neutral gases on passage through an
electric arc give nitric oxide iii] two neutral gases combine to give - a basic gas.
9. Certain thermal decomposition reactions, result in formation of oxides. Give balanced
equations for the thermal decomposition of the following which result information of a metallic oxide
a) Limestone b] Lead carbonate c) Calcium nitrate d] Calcium hydroxide.
10. State the meaning of the term 'oscide. Give a balanced equation for formation of the following oxides -
a) Sulphur dioxide from a non-metal b] Zinc oxide from a metal c) Lead oxide from a mixed osade
11. Give two examples each of the following oxides - a) Acidic oxides b] Basic oxides
c) Amphoteric oxides d) Neutral oxides. State which of the following oxides i.e. a) to d) -
i] React with water to give a base i] React with a base to give salt & water
ii] React with acids & bases to give salt & water.
12 Give one example each of -a] A peroxide b] A mixed oxide c) A dioxide.
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Answer 1

Answer:

Chemical reactions often involve changes in energy due to the breaking and formation of bonds. Reactions in which energy is released are exothermic reactions, while those that take in heat energy are endothermic.