10
MCQ (Single Correct Answer)
The empirical formula and molecular mass of a compound are $\mathrm{CH}_2 \mathrm{O}$ and 180 g respectively. What will be the molecular formula of the compound?
A
$\mathrm{C}_9 \mathrm{H}_{18} \mathrm{O}_9$
B
$\mathrm{CH}_2 \mathrm{O}$
C
$\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$
D
$\mathrm{C}_2 \mathrm{H}_4 \mathrm{O}_2$
11
MCQ (Single Correct Answer)
If the density of a solution is $3.12 \mathrm{~g} \mathrm{~mL}^{-1}$, the mass of 1.5 mL solution in significant figures is ............. .
A
4.7 g
B
$4680 \times 10^{-3} \mathrm{~g}$
C
4.680 g
D
46.80 g
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
$\mathrm{CH}_4(\mathrm{~g})+2 \mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{CO}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{g})$