Concentration of Solutions worksheet - Free Printable

Let's go through each of the questions one by one and verify the solutions, making sure we understand the concepts involved.

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Question 4:

What is the concentration of a solution containing 2.50 moles of sodium chloride in 500 cm³ of water?

Solution:

We use the formula for molar concentration:

\[
\text{Concentration (c)} = \frac{\text{moles (n)}}{\text{volume (v) in dm}^3}
\]

- Moles (n) = 2.50 mol
- Volume = 500 cm³ → convert to dm³:
\( 500\, \text{cm}^3 = 0.500\, \text{dm}^3 \)

Now calculate:

\[
c = \frac{2.50}{0.500} = 5.00\, \text{mol dm}^{-3}
\]

✔ Answer: \( 5.00\, \text{mol dm}^{-3} \) (to 3 significant figures)

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Question 5:

What is the concentration of a solution containing 0.300 moles of potassium hydroxide in 120 cm³ of water?

- Moles (n) = 0.300 mol
- Volume = 120 cm³ = \( 0.120\, \text{dm}^3 \)

\[
c = \frac{0.300}{0.120} = 2.50\, \text{mol dm}^{-3}
\]

✔ Answer: \( 2.50\, \text{mol dm}^{-3} \) (to 3 significant figures)

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Question 6:

What is the concentration of a solution containing 10.0 moles of nitric acid in 20.0 dm³ of water?

- Moles (n) = 10.0 mol
- Volume (v) = 20.0 dm³

\[
c = \frac{10.0}{20.0} = 0.500\, \text{mol dm}^{-3}
\]

✔ Answer: \( 0.500\, \text{mol dm}^{-3} \) (to 3 significant figures)

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Question 7:

What volume is required to make a 2.00 mol dm⁻³ solution starting with 5.00 moles of lead nitrate?

Use the rearranged formula:

\[
v = \frac{n}{c}
\]

- n = 5.00 mol
- c = 2.00 mol dm⁻³

\[
v = \frac{5.00}{2.00} = 2.50\, \text{dm}^3
\]

Convert to cm³ if needed:
\( 2.50\, \text{dm}^3 = 2500\, \text{cm}^3 \)

✔ Answer: \( 2.50\, \text{dm}^3 \) or \( 2500\, \text{cm}^3 \)

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✔ Summary of Answers:

| Question | Answer |
|--------|--------|
| 4 | \( 5.00\, \text{mol dm}^{-3} \) |
| 5 | \( 2.50\, \text{mol dm}^{-3} \) |
| 6 | \( 0.500\, \text{mol dm}^{-3} \) |
| 7 | \( 2.50\, \text{dm}^3 \) (or 2500 cm³) |

All calculations are correct and properly rounded to 3 significant figures as requested.

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🔍 Key Concepts:

- Concentration (mol/dm³) = moles / volume in dm³
- Always convert cm³ to dm³: \( 1\, \text{dm}^3 = 1000\, \text{cm}^3 \)
- Use the formula:
\[
c = \frac{n}{v}, \quad v = \frac{n}{c}, \quad n = c \times v
\]

Let me know if you'd like a visual explanation or help with similar problems!