Question

How many number of atoms are there in four grams of hydrogen gas at $STP$ ?

• A. $6.02\times {10}^{23}$ atoms
• B. $12.04\times {10}^{23}$ atoms
• C. $12.04\times {10}^{46}$ atoms
• D. $1.2\times {10}^{23}$ atoms
• E. $2.40\times {10}^{24}$ atoms

Answer 1

The correct option is E $2.40\times {10}^{24}$ atoms

The molar mass of hydrogen is 2 $g/mol$.
4 grams of hydrogen corresponds to $\frac{4}{2}=2$ moles.
4 grams (2 moles) of hydrogen molecules contains 4 moles of hydrogen atoms.
1 mole of hydrogen atoms corresponds to $6.023\times {10}^{23}$ atoms.
$4\times 6.023\times {10}^{23}=2.40\times {10}^{24}$ hydrogen atoms