Question

Calculate the mass of 25,000 molecules of nitrogen gas. (1 mole = 6.02 x 1023 molecules)

Answer 1

Hey there!

Molar mass N2 = 28.01 g/mol

Therefore:

28.01 g N2 -------------- 6.02*10²² molecules N2

( mass N2 ?? ) ----------- 25,000 molecules N2

mass N2 =  ( 25,000 * 28.01 ) /  ( 6.02*10²³ )

mass N2 = 700250 / 6.02*10²³

mass N2 = 1.163*10⁻¹⁸ g

Hope that helps!

Answer 2

Answer: $116.2\times 10^{-26}$ grams

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:

$\text{Number of moles}=\frac{\text {Given molecules}}{\text {Avogadros number}}$

$\text{Number of moles}=\frac{25000}{6.023\times 10^{23}}=4.15\times 10^{-26}moles$  

Now 1 mole of $N_2$ gas weighs = 28 grams

$4.15\times 10^{-26}moles$ of $N_2$ gas weighs =$\frac{28}{1}\times 4.15\times 10^{-26}=116.2\times 10^{-26}$ grams

Thus the mass will be $116.2\times 10^{-26}$ grams.