Question

What is the temperature change of the sodium chloride pack?

ΔT = Tf - Ti

ΔT = 21°C - 4°C = 17°C

What is the energy change of the sodium chloride pack?

ΔE = 4 kJ/mol

Blank 1:
21
Blank 2:
4
Blank 3:
17
Blank 4:
4
Question 2
Is this reaction endothermic or exothermic?

a
Endothermic
b
Exothermic
Question 3
Does this reaction make a hot or cold pack?

a
Hot pack
b
Cold pack

Answer 1

Let's address each component of your questions step by step.

**Question 1:**
You have already calculated the temperature change (ΔT) of the sodium chloride pack:
- Final temperature (Tf) = 21°C
- Initial temperature (Ti) = 4°C
- ΔT = Tf - Ti = 21°C - 4°C = 17°C

You mentioned an energy change (ΔE) of 4 kJ/mol. Based on your provided statements, the following blanks can be filled:
- **Blank 1**: 21 (Final temperature)
- **Blank 2**: 4 (Initial temperature)
- **Blank 3**: 17 (Temperature change, ΔT)
- **Blank 4**: 4 (Energy change, ΔE in kJ/mol)

**Question 2:**
To determine if the reaction is endothermic or exothermic, consider the following:
- **Endothermic**: Absorbs heat from the surroundings (temperature decreases in the surroundings).
- **Exothermic**: Releases heat to the surroundings (temperature increases in the surroundings).

Since you have observed the temperature rising from 4°C to 21°C, it suggests that the process results in heat release to the surroundings.
Thus, if the sodium chloride is used in a process that absorbs heat, it would be considered endothermic, but given the context, we can conclude:

- **Answer**: a) Endothermic

**Question 3:**
Given that the sodium chloride pack decreases the temperature of the surroundings (indicated by the increase in temperature of the pack from a cold starting point), this is consistent with the characteristics of a cold pack.

- **Answer**: b) Cold pack

In summary:
- Blank 1: 21
- Blank 2: 4
- Blank 3: 17
- Blank 4: 4
- Question 2: a) Endothermic
- Question 3: b) Cold pack