Question

Sodium hydroxide, NaOH, is a strong base that is used in industrial synthesis and processes such as making paper. What is the mass of 2.80 ×1022 molecules of NaOH (Molar mass = 40.0 g/mol)?

Answer 1

Answer:

1.86 g

Explanation:

We must convert formula units of NaOH to moles and then to mass of NaOH.

Step 1. Convert molecules to moles

$\text{Moles of NaOH} = 2.80 \times 10^{22}\text{ units NaOH} \times \frac{ \text{1 mol NaOH}}{ 6.022 \times 10^{23} \text{ units NaOH}} = \text{0.046 50 mol NaOH}$

Step 2. Convert moles to grams

$\text{Mass of NaOH} = \text{0.046 50 mol NaOH} \times \frac{\text{40.0 g NaOH} }{ \text{1 mol NaOH}} = \text{1.86 g NaOH}$

Answer 2

Answer:

Mass of $2.80\times 10^{22}$  molecules of NaOH = 1.86 g

Explanation:

Avogadro’s number represent the number of the constituent particles which are present in one mole of the substance. It is named after scientist Amedeo Avogadro and is denoted by $N_0$.

Avogadro constant:-

$N_a=6.023\times 10^{23}$

So,

$6.023\times 10^{23}$  molecules of NaOH are present in 1 mole of NaOH

Given, Molar mass of NaOH = 40.0 g/mol

This means, mass of 1 mole of NaOH = 40 g

So,

$6.023\times 10^{23}$  molecules of NaOH weighs 40 g

1  molecule of NaOH weighs $\frac{40}{6.023\times 10^{23}}$ g

$2.80\times 10^{22}$  molecules of NaOH weighs $\frac{40}{6.023\times 10^{23}}\times 2.80\times 10^{22}$ g

Mass of $2.80\times 10^{22}$  molecules of NaOH = 1.86 g