Given:
mass of Na₂SO₄ = 25.0 g
Required:
moles of Na
number of Na particles
Solution: (moles of Na)
Step 1: Calculate the molar mass of Na₂SO₄.
molar mass of Na₂SO₄ = (22.99 g/mol × 2) + (32.07 g/mol × 1) + (16.00 g/mol × 4)
molar mass of Na₂SO₄ = 142.05 g/mol
Step 2: Calculate the number of moles of Na by using dimensional analysis.
Since there are 2 mol of Na in 1 mol of Na₂SO₄, the number of moles of Na is
[tex]\text{moles of Na = 25.0 g} \: \text{Na}_{2}\text{SO}_{4} × \frac{\text{1 mol} \: \text{Na}_{2}\text{SO}_{4}}{\text{142.05 g} \: \text{Na}_{2}\text{SO}_{4}} × \frac{\text{2 mol Na}}{\text{1 mol} \: \text{Na}_{2}\text{SO}_{4}}[/tex]
[tex]\text{moles of Na = 0.3519887 mol}[/tex]
[tex]\boxed{\text{moles of Na = 0.352 mol}}[/tex]
Solution: (number of Na particles)
[tex]\text{number of Na particles = 0.3519887 mol Na} × \frac{6.022 × 10^{23} \: \text{Na particles}}{\text{1 mol Na}}[/tex]
[tex]\boxed{\text{number of Na particles} = 2.12 × 10^{23} \: \text{particles}}[/tex]
[tex]\\[/tex]
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