Question

How many SO32- ions are contained in 99.6 mg of Na2SO3? The molar mass of Na2SO3 is 126.05 g/mol.

Answer 1

1) Na2SO3 = 2Na(+) + SO3 (2-)

=> 1 mol SO3 (2-) : 1 mol Na2SO3

2) Molar mass of Na2 SO3

2*23 g/mol + 32g/mol + 3*16 g/mol = 126 g/mol

3) moles of Na2SO3

n = grams / molar mass = 99.6mg * [1 g /1000 mg] / 126 g / mol = 7.9*10^-4 mol Na2SOs

4) moles of ions

1 mol SO3 (2-) : 1 mol Na2SO3 => 7.9*10^-4 mol Na2SO3 = 7.9*10^-4 mol SO3 (2-)

5) number of ions

number of ions = number of ions * Avogadro number

number of ions = 7.90 * 10^-4 mol * 6.022 * 10^23 ions / mol = 0.0048 * 10^23 ions = 4.8 * 10^ 20 ions

Answer: 4.8 * 10^20 ions