Question

Find the number of sodium and sulphate ions in 14.2g of sodium sulphate.

Answer 1

Sodium sulfate is Na_2 ,SO_4
First, calculate the moles of sodium sulfate you have in a 14.2g sample.

1. Find the molar mass of sodium sulfate
   molar mass = Atomic mass in grams
   2(23) + 32 + 4(16) = 142 grams per mole
2. Divide the mass of the sample by the molar mass to obtain moles
   (14.2g)/(142gmol^-1) = 0.1 mol

Now, for every 1 mol of Na_2 ,SO_4 you have 2 moles of Na^+ ions. Multiple the moles of Na_2 ,SO_4 that you found just then by 2 to obtain the moles of sodium ions.

Use Avogadro's number (6.022 x 10^23) to find the number of ions present. (Recall that Avogrado's number is the number of particles per mole of a substance).

6.022 x 10^23 x 0.2 mol = 1.2044 x 10^23ions