Question

maximum number of molecules is present in 15 l of h2 gas at stp

Answer 1

no. of molecules=no. of moles×Na
and no.of moles=given volume(in litre)/22.4
so,
no. of molecules=vol. ×Na/22.4
no. of molecules=15×Na/22.4
is the answer
where Na is Avogadro's no

Answer 2

Answer: $4.03\times 10^{23}$ molecules.

Explanation: According to Avogadro's law, 1 mole of every substance occupies 22.4 Liters at NTP and contains avogadro's number  of particles.

$\text{Number of moles}=\frac{\text{Given volume}}{\text {Molar volume}}$

$\text{Number of moles}=\frac{15L}{22.4L}=0.67moles$

Now 1 mole of $H_2$ molecule contains = $6.023\times 10^{23}$ molecules

0.67 moles of $H_2$ molecule contains =$\frac{6.023\times 10^{23}}{1}\times 0.67=4.03\times 10^{23}$ molecules.