12
MCQ (Single Correct Answer)
Which of the following statements about a compound is incorrect?
A
A molecule of a compound has atoms of different elements
B
A compound cannot be separated into its constituent elements by physical methods of separation
C
A compound retains the physical properties of its constituent elements
D
The ratio of atoms of different elements in a compound is fixed
13
MCQ (Single Correct Answer)
Which of the following statements is correct about the reaction given below?
$$4 \mathrm{Fe}(s)+3 \mathrm{O}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{Fe}_2 \mathrm{O}_3(\mathrm{~g})$$
A
Total mass of iron and oxygen in reactants $=$ total mass of iron and oxygen in product therefore it follows law of conservation of mass
B
Total mass of reactants $=$ total mass of product, therefore, law of multiple proportions is followed
C
Amount of $\mathrm{Fe}_2 \mathrm{O}_3$ can be increased by taking any one of the reactants (iron or oxygen) in excess
D
Amount of $\mathrm{Fe}_2 \mathrm{O}_3$ produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess
14
MCQ (Single Correct Answer)
Which of the following reactions is not correct according to the law of conservation of mass?
A
$2 \mathrm{Mg}(\mathrm{s})+\mathrm{O}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{MgO}(\mathrm{s})$
B
$\mathrm{C}_3 \mathrm{H}_8(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g})+\mathrm{H}_2 \mathrm{O}(\mathrm{g})$
C
$\mathrm{P}_4(\mathrm{~s})+5 \mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{P}_4 \mathrm{O}_{10}(\mathrm{~s})$
D
$\mathrm{CH}_4(\mathrm{~g})+2 \mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{g})$
15
MCQ (Single Correct Answer)
Which of the following statements indicates that law of multiple proportion is being followed?
A
Sample of carbon dioxide taken from any source will always have carbon and oxygen in the ratio $1: 2$
B
Carbon forms two oxides namely $\mathrm{CO}_2$ and CO , where masses of oxygen which combine with fixed mass of carbon are in the simple ratio $2: 1$
C
When magnesium burns in oxygen, the amount of magnesium taken for the reaction is equal to the amount of magnesium in magnesium oxide formed
D
At constant temperature and pressure 200 mL of hydrogen will combine with 100 mL oxygen to produce 200 mL of water vapour
16
MCQ (Multiple Correct Answer)
One mole of oxygen gas at STP is equal to .........
A
$6.022 \times 10^{23}$ molecules of oxygen
B
$6.022 \times 10^{23}$ atoms of oxygen
C
16 g of oxygen
D
32 g of oxygen