How many cations are there in 40.0 g of sodium phosphate?

Formula of sodium phosphate is

The molar mass of compound,

Mass of compound, m = 30 g

Number of mol is mass of compound divided by its molar mass as below:

n = m /M

Mole can be expressed as:

Number of particle /N_A = n = 0.182 mol

Number of particle

As 3 sodium or cation are present in compound

Thus, 3.3 * 10^23  cation are present in 30 g sodium phosphate

There are 4.41 × 10²³ cations in 40.0 g of sodium phosphate.

First, we will convert 40.0 g of Na₃PO₄ to moles using its molar mass (163.94 g/mol).

Then, we will convert 0.244 moles to molecules using Avogadro's number: there are 6.02 × 10²³ molecules of Na₃PO₄ in 1 mole of molecules of Na₃PO₄.

Sodium phosphate is a strong electrolyte that dissociates according to the following equation.

Na₃PO₄ ⇒ 3 Na⁺ + PO₄³⁻

As we can see, there are 3 Na⁺ cations per molecule of Na₃PO₄. The number of  Na⁺ cations in 1.47 × 10²³ molecules of Na₃PO₄ are:

There are 4.41 × 10²³ cations in 40.0 g of sodium phosphate.

You can learn more about Avogadro's number here: