Which of the following contain the same number of atoms?

(Given : Molar mass in $\mathrm{g} \mathrm{mol}^{-1}$ of $\mathrm{H}, \mathrm{He}, \mathrm{O}$ and S are 1, 4, 16 and 32 respectively)

A. 2 g of $\mathrm{O}_2$ gas

B. 4 g of $\mathrm{SO}_2$ gas

C. 1400 mL of $\mathrm{O}_2$ at STP

D. $0.05 \mathrm{~L}$ of He at STP

E. $ 0.0625 \mathrm{~mol}$ of $\mathrm{H}_2$ gas

Choose the correct answer from the options given below :

An oxide of iron contains $69.9 \%$ iron, its empirical formula, is :

(Given : Molar mass of Fe and O are 56 and $16 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively.)

What volume of hydrogen gas at STP would be liberated by action of 50 mL of $\mathrm{H}_2 \mathrm{SO}_4$ of $50 \%$ purity (density $=1.3 \mathrm{~g} \mathrm{~mL}^{-1}$ ) on 20 g of zinc?

Given : Molar mass of $\mathrm{H}, \mathrm{O}, \mathrm{S}, \mathrm{Zn}$ are 1, 16, 32, $65 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively.

How many grams of residue is obtained by heating 2.76 g of silver carbonate?

(Given : Molar mass of $\mathrm{C}, \mathrm{O}$ and Ag are 12, 16 and $108 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively)