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

Mass of
`2.80* 10^(22)` molecules of NaOH = 1.86 g

Step-by-step 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* 10^(23)`

So,

`6.023* 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* 10^(23)` molecules of NaOH weighs 40 g

1 molecule of NaOH weighs
`(40)/(6.023* 10^(23))` g

`2.80* 10^(22)` molecules of NaOH weighs
`(40)/(6.023* 10^(23))* 2.80* 10^(22)` g

Mass of
`2.80* 10^(22)` molecules of NaOH = 1.86 g

Answer 2

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 * 10^(22)\text{ units NaOH} * \frac{ \text{1 mol NaOH}}{ 6.022 * 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} * \frac{\text{40.0 g NaOH} }{ \text{1 mol NaOH}} = \text{1.86 g NaOH}`