Let’s solve the first problem on the worksheet:
Problem 1: What is the molarity of a 0.30 liter solution containing 0.50 moles of NaCl?
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Step-by-step reasoning:
We are given:
- Moles of solute (NaCl) =
0.50 mol
- Volume of solution =
0.30 L
The formula for molarity is:
>
M = n / V
Where:
- M = molarity (in mol/L or M)
- n = number of moles
- V = volume in liters
Plug in the numbers:
> M = 0.50 mol ÷ 0.30 L
Do the division:
> 0.50 ÷ 0.30 = 1.666...
Round to two significant figures (since both 0.50 and 0.30 have two sig figs):
> ≈
1.7 M
Wait — let’s double-check that rounding.
Actually, 0.50 has two sig figs, 0.30 also has two sig figs → so answer should have two sig figs.
0.50 ÷ 0.30 = 1.666... → rounds to
1.7
But hold on — sometimes in chemistry, if the leading digit is 1, we might keep an extra digit? No — standard rule: count sig figs from the inputs. Both have two → answer has two.
So 1.7 M is correct.
Alternatively, write as fraction:
0.50 / 0.30 = 5/3 ≈ 1.666... → still 1.7 with two sig figs.
✔ Confirmed.
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Final Answer:
1.7 M
Parent Tip: Review the logic above to help your child master the concept of molarity worksheet.
