Question

1. a balloon contains 4.50×10²¹ atoms of helium (he) gas. calculate the mass of helium in grams. 0.185 g 0.0185 g 0.0747 g 0.299 g clear all

Explanation:

Step1: Recall Avogadro's number

Avogadro's number ($N_A$) is $6.022\times 10^{23}$ atoms/mol.

Step2: Calculate the number of moles of helium

The number of moles ($n$) of helium is given by $n=\frac{N}{N_A}$, where $N = 4.50\times 10^{22}$ atoms. So $n=\frac{4.50\times 10^{22}}{6.022\times 10^{23}}$ mol.
$n=\frac{4.50}{6.022}\times10^{- 1}\text{ mol}\approx0.0747\text{ mol}$

Step3: Use molar - mass of helium

The molar mass of helium ($M$) is $4.00\text{ g/mol}$. The mass ($m$) of helium is calculated using the formula $m = n\times M$.
$m=0.0747\text{ mol}\times4.00\text{ g/mol}=0.299\text{ g}$

Answer:

$0.299\text{ g}$