Question

What is the mass of 40.34 x 10^23 H2 molecules at stp?

Answer 1

Answer: The mass of hydrogen gas for the given number of molecules is 13.4 g

Explanation:

We are given:

Number of hydrogen gas molecules = $40.34\times 10^{23}$

At STP conditions:

$6.022\times 10^{23}$ number of molecules are contained in 1 mole of a gas.

So, $40.34\times 10^{23}$ number of molecules will be contained in =  $\frac{1}{6.022\times 10^{23}}\times 40.34\times 10^{23}=6.7mol$ of hydrogen gas.

To calculate the mass of hydrogen gas, we use the equation:

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

Moles of hydrogen gas = 6.7 moles

Molar mass of hydrogen gas = 2 g/mol

Putting values in above equation, we get:

$6.7mol=\frac{\text{Mass of hydrogen gas}}{2g/mol}\\\\\text{Mass of hydrogen gas}=13.4g$

Hence, the mass of hydrogen gas for the given number of molecules is 13.4 g

Answer 2

Every mol=6.22*10^23 molecules and every mol of H2 Is 2 gram
40.34*10^23/6.22*10^23=6.48 or 6.5
6.5*2=13 gram