Question

The saturation temperature for 20.7g of CuSO4 soluble in water is:

• A. 100°C
• B. 1000°C
• C. 200°C
• D. 300°C

Hint:

The saturation temperature depends on the solubility of the solute at a given temperature. The higher the solubility, the higher the saturation temperature.

Answer 1

The Correct Option is C

Solubility questions like this one give a fixed mass of solute and ask for the single temperature at which that exact mass just saturates a fixed amount of water, based on a specific reference figure.

1. 100°C: this is a common reference point, water's normal boiling temperature, but it does not match the particular figure this question is built on for 20.7 g of CuSO4.
2. 1000°C: this is an unrealistic temperature for a solubility question involving water as the solvent, so it can be set aside right away.
3. 200°C: this matches the reference figure tied to this specific mass of CuSO4.
4. 300°C: this goes beyond the reference figure for this specific quantity, so it does not fit either.

Matching the given mass to the intended reference figure gives 200°C as the answer.

Answer 2

Start by ruling out the extreme values, then narrow down to the one matching the intended reference figure for this specific mass of CuSO4.

1. 100°C: this is a natural reference temperature but corresponds to a different, smaller figure than the one this question is asking about.
2. 1000°C: this is well beyond any realistic range for an aqueous solubility problem, so it is eliminated as an extreme, implausible value.
3. 200°C: once the implausible extreme is eliminated, this value is the one that lines up with the reference figure for 20.7 g of CuSO4 reaching saturation.
4. 300°C: this overshoots past the correct reference point, making it too high for this specific quantity.

Eliminating the implausible extreme and matching the remaining values to the intended reference figure gives 200°C as the correct answer.