Question

how many atoms of hydrogen are thete in 2.57×10^-6g of hydrogen

Answer 1

no. of atoms in 1g of hydrogen= 6.022×10^23
no. of atoms in 2.57×10^-6 of hydrogen= 6.022×10^23 × 2.57×10^-6
= 15.57 × 10^17 atoms

Answer 2

$15.4\times 10^{17}$  atoms of hydrogen are there in $1.28\times 10^{-6}$   of hydrogen

Explanation:

According to avogadro's law, 1 mole of every substance weighs equal to the molecular mass and contains avogadro's number $6.023\times 10^{23}$ of particles.

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{2.57\times 10^{-6}g}{2g/mol}=1.28\times 10^{-6}moles$

1 mole of $H_2$ contains = $2\times 6.023\times 10^{23}=12.05\times 10^{23}$ atoms of hydrogen

Thus $1.28\times 10^{-6}$  moles of $H_2$ contain=$\frac{12.05\times 10^{23}}{1}\times 1.28\times 10^{-6}=15.4\times 10^{17}$  atoms of hydrogen

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