Question

Question #994e2

Answer 1

`30.`g

Explanation:

A 3.0 M solution of NaOH has 3.0 moles of NaOH per liter of solution. There are 0.25 L of solution `(250"mL" * (1"L")/(1000"mL"))`, so there are `0.25"L" * 3.0"mol/L" = 0.75"mol"` of NaOH. The molar mass of NaOH is 40.0 g/mol, so there are `0.75"mol" * 40.0"g/mol" = 30"g"` of NaOH, 30. g with the right number of significant figures.

Answer 2

30 g.

Explanation:

It's a 3.0 M solution so 1 litre of solution contains 3 moles of NaOH. 250 ml of solution therefore contains 0.25 x 3 = 0.75 moles of NaOH.

The molar mass of NaOH is 39.9971 g/mol, so 250 ml of this solution contains 0.75 x 39.9971 = 29.99 g, or if you round it up 30.0 g.