Question

1. if you want to dissolve 40.2 g of kcl in 100 g of water, what temperature should the water be?

solubilities of solutes in water at various temperatures

substance	formula	solubility g/100 g h₂o*
aluminum sulfate	al₂(so₄)₃	31.2	36.4	59.2	89.0
barium hydroxide	ba(oh)₂	1.67	3.89	20.94	-
calcium hydroxide	ca(oh)₂	0.189	0.173	0.121	0.076
lithium sulfate	li₂so₄	36.1	34.8	32.6	-
potassium chloride	kcl	28.0	34.2	45.8	56.3

options: 0°c, 20°c, 60°c, 100°c

Explanation:

Step1: Identify KCl solubility data

From the table, KCl solubility (g/100g H₂O) at different temps: 0°C (28.0), 20°C (34.2), 60°C (45.8), 100°C (56.3).

Step2: Compare with 40.2 g

We need solubility ≥ 40.2 g/100g H₂O.

• 0°C: 28.0 < 40.2
• 20°C: 34.2 < 40.2
• 60°C: 45.8 > 40.2
• 100°C: 56.3 > 40.2 (but 60°C is lower temp with solubility >40.2? Wait, no—wait, 40.2 is between 34.2 (20°C) and 45.8 (60°C). Wait, 40.2 is less than 45.8 (60°C) and more than 34.2 (20°C). Wait, the question is "what temperature should the water be" to dissolve 40.2 g. So the solubility at that temp must be at least 40.2 g/100g H₂O (since we need to dissolve 40.2 g in 100 g water). So check which temp has solubility ≥40.2.

60°C: 45.8 ≥40.2
100°C: 56.3 ≥40.2

But 60°C is lower than 100°C, and 45.8 is just above 40.2. Wait, did I misread? Wait KCl at 60°C is 45.8, which is more than 40.2. At 20°C, 34.2 <40.2. So 60°C is the first temp where solubility exceeds 40.2. Wait, but 40.2 is between 34.2 (20°C) and 45.8 (60°C). So to dissolve 40.2 g, the solubility must be ≥40.2, so 60°C (45.8) works, 100°C also works, but 60°C is an option. Wait the options are 0,20,60,100. So 60°C has solubility 45.8, which is more than 40.2, so it can dissolve. 20°C: 34.2 <40.2, can't. 0°C: 28 <40.2. 100°C: 56.3, but 60°C is a valid option (and lower temp, but the question is which temp "should" it be—so the minimum temp where solubility ≥40.2. So 60°C is the correct option here.

Answer:

60°C (Option: 60°C)