Question

The group of students then did an experiment using four different solutes to see which one would be best in their hot pack. To determine which solute would be best, the students mixed 20 g of each solute into separate containers that each held 50 mL of 24°C water. The students then recorded the temperature changes in each container. The data table below shows the maximum and minimum temperature they obtained for each solute, as well as the temperature difference.

Maximum Temperature (°C) Minimum Temperature (°C) Temperature Difference (°C)
Ammonium chloride (NH4Cl) 24 1 23
Calcium chloride (CaCl2) 60 24 36
Sodium acetate (CH3COONa) 55 24 31
Sodium chloride (NaCl) 24 22 2

According to the students' data, which solute should they use in their hot pack?
A.
calcium chloride
B.
sodium chloride
C.
sodium acetate
D.
ammonium chloride

Answer 1

To determine which solute would be best for the hot pack, we should look for the solute that resulted in the highest temperature difference, as a greater temperature difference indicates a more effective release of heat when the solute dissolves.

Based on the provided data:

- Ammonium chloride (NH4Cl): Temperature difference = 23°C
- Calcium chloride (CaCl2): Temperature difference = 36°C
- Sodium acetate (CH3COONa): Temperature difference = 31°C
- Sodium chloride (NaCl): Temperature difference = 2°C

The calcium chloride (CaCl2) had the highest temperature difference of 36°C, which means it produced the highest amount of heat when dissolved in water.

Therefore, the students should use **A. calcium chloride** in their hot pack.