Exothermic and endothermic reactions

Question 10

Medium

A student investigated the temperature change when different masses of anhydrous ammonium nitrate were dissolved in water.

Method:

Measure $cm350\text{ cm}^3$ of water into a polystyrene cup.
Measure the initial temperature of the water.
Add a known mass of ammonium nitrate to the water.
Stir the mixture until all the ammonium nitrate has dissolved.
Measure the lowest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of ammonium nitrate.

Table 1: Results of the investigation

Mass of ammonium nitrate added ( $g\text{g}$ )	Lowest temperature of solution ( $∘C^{\circ}\text{C}$ )
$3.0$	$17.9$
$6.0$	$14.3$
$9.0$	$10.7$
$12.0$	$7.1$
$15.0$	$3.5$

Questions:

Identify the independent variable and the dependent variable in this investigation.

[2]

Determine the initial temperature of the water by extrapolating the linear data to a mass of $g0\text{ g}$ .

[2]

State whether the dissolving of ammonium nitrate is exothermic or endothermic, and justify your answer.

[2]

The student repeated the experiment four times using $g9.0\text{ g}$ of ammonium nitrate. The lowest temperatures recorded were $∘C10.4\ ^{\circ}\text{C}$ , $∘C11.2\ ^{\circ}\text{C}$ , $∘C10.9\ ^{\circ}\text{C}$ , and $∘C10.7\ ^{\circ}\text{C}$ . Calculate the mean lowest temperature and the uncertainty (using $±range2\pm \frac{\text{range}}{2}$ ). Express your final answer in the format $mean±uncertainty\text{mean} \pm \text{uncertainty}$ .

[2]

Exothermic and endothermic reactions

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Question 10

Medium

A student investigated the temperature change when different masses of anhydrous ammonium nitrate were dissolved in water.

Method:

Measure $cm350\text{ cm}^3$ of water into a polystyrene cup.
Measure the initial temperature of the water.
Add a known mass of ammonium nitrate to the water.
Stir the mixture until all the ammonium nitrate has dissolved.
Measure the lowest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of ammonium nitrate.

Table 1: Results of the investigation

Mass of ammonium nitrate added ( $g\text{g}$ )	Lowest temperature of solution ( $∘C^{\circ}\text{C}$ )
$3.0$	$17.9$
$6.0$	$14.3$
$9.0$	$10.7$
$12.0$	$7.1$
$15.0$	$3.5$

Questions:

Identify the independent variable and the dependent variable in this investigation.

[2]

Determine the initial temperature of the water by extrapolating the linear data to a mass of $g0\text{ g}$ .

[2]

State whether the dissolving of ammonium nitrate is exothermic or endothermic, and justify your answer.

[2]

Exothermic and endothermic reactions

Question 10

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions

Exothermic and endothermic reactions

Question 10

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions