Question

27:

27 Number of molecules in 100 ml of each of O2,NH₃ and CO₂ at STP are
(a) In the order CO₂ < O₂ < NH₃
(b) In the order NH₃ < O₂ < CO₂
(c) The same (d) NH₃ = CO₂ < O₂

Answer 1

Dear Student

1 mole of any gas occupies a volume of 22.4 L at STP

So, 0.1 L (or 100 ml) of any gas at STP will have $\frac{1}{22.4L}$ x 0.5 L moles (volume would be same for all the 3 gases)
Now, 1 mole of any substance contains 6.022 x 10²³ molecules
So, $\frac{0.5}{22.4L}$moles will include $\frac{0.5x6.023x{10}^{23}}{22.4}$ molecules (for all the 3 gases) = 0.1344 x 10²³ molecules

Therefore, the answer would be (c).

Regards