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