A student added a sample of NH4NO3 to water and measured the temperature over time. What is the value of that the student should use to calculate ?

a) Change in temperature = -2.6°C

b) The reaction is an exothermic reaction as the temperature of the reaction solution reduces after the reaction has taken place.

Explanation:

The image of the complete question is attached to this solution.

For the change in temperature that will be used to calculate q, the heat given off or absorbed, we just read the initial and final temperature of the solution from the graph.

From the graph,

Initial Temperature of the solution = 24.8°C

Final Temperature of the solution = 22.2°C

Change in temperature = ΔT = (final temperature) - (Initial temperature)

= 22.2 - 24.8 = -2.6°C

b) An exothermic reaction is on in which heat is lost to the environment. It has a negative heat of reaction to indicate the loss of heat to the environment. The energy content of the products are lesser than the energy content of the reactants, hence, this heat loss happens. And logically. A system that loses heat to the surroundings will have its system temperature lowered to account for the heat lost to the environment.

While an emdothermic reaction is one in which heat is gained from the environment. The heat of reaction is positive to indicate this heat gain.

An endothermic reaction gains heat from the environment thereby leading to an expected higher final temperature after the reaction than the initial temperature before the reaction.

Since the temperature of this reaction reduces evidently from the graph, it points to a loss of heat to the surroundings, further pointing towards an exothermic reaction.

Hope this Helps!!!

The student should use the final and initial temperature of the solution to calculate the difference.

Exothermic Reaction:

The reaction in which the heat is released during the reaction. The energy of the product is less.

For example:

When Ammonium nitrate reacts with water energy is released.

The temperature difference calculated by the formula,

Where,

Ti - Initial temperature = 24.8

- Final temperature = 22.2

Put the values in the formula,

Therefore, the student should use the final and initial temperature of the solution to calculate the difference.

To know more about Exothermic reaction,

link

it is b that is the answer.