Answer:
Explanations:
1) According to the first question, we are to find the molar mass of Na₂SO₄.
Find the molar mass of each element present on the compound
• Molar mass of Sodium (Na) = 23g/mol
,• Molar mass of sulfur (S) = 32g/mol
,• Molar mass of Oxygen (O) = 16g/mol
Get the molar mass of Na₂SO₄.
[tex]\begin{gathered} \text{Molar mass of }Na_{2}SO_{4}=2(23)+32+4(16) \\ \text{Molar mass of }Na_2SO_4=46+32+64 \\ \text{Molar mass of }Na_{2}SO_{4}=142g\text{/mol} \end{gathered}[/tex]Therefore the molar mass of Na₂SO₄ is 142g/mol
2) The formula for calculating the number of moles of the compound Na₂SO₄ is expressed as:
[tex]n=\text{Molar conc.}\times\text{volume}[/tex]Given the following parameters:
• Molar concentration = 0.202M = 0.202mol/L
,• Volume = 784mL= 0.784L
Substitute the given parameters into the formula:
[tex]\begin{gathered} n=0.202\frac{mol}{\cancel{L}}\times0.784\cancel{L} \\ n=0.1584\text{moles} \end{gathered}[/tex]Hence the number of Na₂SO₄ needed is 0.1584moles.