EASY
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A gas is always evolved in a chemical reaction.

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Important Questions on Chemical Reactions

MEDIUM
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
In certain reactions a change of state is observed i.e. solid to liquid, liquid to gas etc. State the change of state of the reactants to give the respective products in each case.
(a) C+2S→ CS2
(b) NH3+HCl⇌ NH4Cl
(c) 2H2+O2→2H2O
(d) 2H2O→Electric current2H2+O2
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Gas evolved when potassium chlorate is heated:
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
A _____ is an insoluble solid formed during a chemical reaction. 
HARD
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions

Explain the following:

The mass of reactants in a chemical reaction does not change.

EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Which one of these reactions show the formation of precipitate?
HARD
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Aqueous solution of which of the following is colourless?
MEDIUM
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
In certain reactions, a change of smell is observed. Give two examples from the daily life of the same.
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
The formation of gas bubbles in a liquid during a reaction is called _____.
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Which of these is an indication of the evolution of gas in a reaction?
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
The gas evolved indicated with _____ in the chemical equation.
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Name the gas formed when aluminium carbide is treated with water.
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions

Which one of these is a characteristic of a chemical reaction? 

MEDIUM
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
An iron nail is suspended in copper sulphate solution and kept for a while. It is observed that the solution:
HARD
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
A chemical reaction is generally accompanied by certain external indications or characteristics. These include - change of - a] colour b] state c] smell d] evolution of gas e] formation of precipitate f] evolution or absorption of heat. With reference to change of colour - state the change in colour seen when the following are heated.
(i) Copper carbonate
(ii) Zinc carbonate
(iii) Mercury[II] oxide
(iv) Lead [IV] oxide.
MEDIUM
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
A chemical reaction in which heat is given out is called an _____ reaction. (exothermic/endothermic)
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Sodium reacts with water to liberate _____ gas.
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
When one or more substances (elements or compounds), undergo a chemical change, with the absorption or release of energy, so as to form one or more products, the changes taking place collectively is called a _____.
MEDIUM
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Endothermic reactions are characterised by _____ of energy.
HARD
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Rekha took two solutions, 10 mL each separately in two test tubes A and B. The solutions were of FeSO4 and Al2SO43, respectively. The colours of the two solutions were:
EASY
Science>Chemistry>Chemical Reactions>Characteristics of chemical reactions
Write the chemical reactions involved when Zn(s) reacts with sulphuric acid.