Question

1. what is the molar mass of na₂so₄?
2. what is the mass, in grams, of 2.0 moles of co₂ gas?

Explanation:

Step1: Find molar mass of $\text{Na}_2\text{SO}_4$

Look up atomic masses: $\text{Na}=23\ \text{g/mol}$, $\text{S}=32\ \text{g/mol}$, $\text{O}=16\ \text{g/mol}$.
$$M(\text{Na}_2\text{SO}_4) = 2\times23 + 32 + 4\times16$$
$$M(\text{Na}_2\text{SO}_4) = 46 + 32 + 64 = 142\ \text{g/mol}$$

Step2: Find molar mass of $\text{CO}_2$

Atomic masses: $\text{C}=12\ \text{g/mol}$, $\text{O}=16\ \text{g/mol}$.
$$M(\text{CO}_2) = 12 + 2\times16$$
$$M(\text{CO}_2) = 12 + 32 = 44\ \text{g/mol}$$

Step3: Calculate mass of 2.0 mol $\text{CO}_2$

Use $m = n\times M$, where $n=2.0\ \text{mol}$.
$$m(\text{CO}_2) = 2.0\ \text{mol} \times 44\ \text{g/mol} = 88\ \text{g}$$

Answer:

1. The molar mass of $\text{Na}_2\text{SO}_4$ is $142\ \text{g/mol}$
2. The mass of 2.0 moles of $\text{CO}_2$ gas is $88\ \text{g}$