Question

How many grams of Na2SO4 should be weighed out to prepare 0.5L of a 0.100M solution​

Answer 1

• 7 g.

Step-by-step explanation:

The symbol M in 0.100 M means molarity.

Molarity is the unit of concentration that indicates the number of moles of solute in 1 liter of solution:

• M = moles of solute / liters of solution.

You have 0.5 liters of the solution, so you have:

• moles of solute = M × number of liters = 0.5 liters × 0.100 M = 0.05 moles.

Now to convert moles of Na₂SO₄ to mass in grams you use the molar mass of Na₂SO₄:

• molar mass of Na₂SO₄ = 142 g/mol

• molar mass = mass in grams /number of moles

• mass in grams = molar mass × number of moles = 0.05 mol × 142 g/mol = 7.1 g

Rounded to 1 significant figure: 7 g.