Question

The maximum number of molecules is present in

• A. 10 g of $O_2$ gas
• B. 15 L of $H_2$ gas at S.T.P
• C. 5 L of $N_2$ gas at S.T.P
• D. 0.5 g of $H_2$ gas

Answer 1

Answer: (B)

15 L of $H_2$ gas at S.T.P

Answer 2

Calculate number of molecules (n) for each of the given options,

In 15 L of H2 gas at STP,

n = $\frac{6.023 \times 10^{23}}{22.4} \times 15 = 4.033 \times 10^{23}$

In 0.5 g of H2 gas,

n = $\frac{6.023 \times 10^{23} \times 0.5}{2} = 1.505 \times 10^{23}$

In 5 L of N2 gas at STP,

n = $\frac{6.023 \times 10^{23} \times 5}{22.4} = 1.344 \times 10^{23}$

In 10 g of O2 gas,

n = $\frac{6.023 \times 10^{23} \times 10}{32} = 1.882 \times 10^{23}$

**The maximum number of molecules are present in 15 L of H 2 gas at STP, hence option B is correct. **

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