Question

Approximately, how many kg of Potassium Nitrate can be dissolved in 10 litres of water at 30$^\circ$C?

• A. 0.04
  (b) 0.4
  (c) 4
  (d) 0.35
• B. 0.4
• C. 4
• D. 0.35

Hint:

When given solubility in kg/L and asked for multiple litres, multiply directly — be careful not to confuse per litre values with totals.

Answer 1

The Correct Option is B

From the graph, at 30°C, the solubility of Potassium Nitrate (▲) is approximately 0.04 kg/L of water.
This means that in 1 litre of water, 0.04 kg can dissolve.
For 10 litres of water: \[ 0.04 \, \text{kg/L} \times 10 \, \text{L} = 0.4 \, \text{kg} \] Thus, approximately 0.4 kg of Potassium Nitrate can be dissolved in 10 litres of water at this temperature.
Option (a) 0.04 — this is the amount per litre, not for 10 litres.
Option (c) 4 — would require 1 kg/L solubility, which is far above the actual value.
Option (d) 0.35 — close but slightly lower than the calculated result; graph clearly shows about 0.04 per litre, so 0.4 for 10 litres is correct.