Exothermic and endothermic reactions

Question 6

Medium

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

Method:

Measure $cm3100\text{ cm}^3$ of water into a polystyrene cup.
Measure the initial temperature of the water.
Add a known mass of calcium chloride to the water.
Stir the mixture until all the calcium chloride has dissolved.
Measure the highest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of calcium chloride.

Table 1: Results of the investigation

Mass of calcium chloride added (g)	Highest temperature of solution ( $∘C^{\circ}\text{C}$ )
$2.0$	$24.0$
$4.0$	$28.0$
$6.0$	$32.0$
$8.0$	$36.0$
$10.0$	$40.0$

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 calcium chloride is exothermic or endothermic, and justify your answer.

[2]

The student repeated the experiment four times using $g6.0\text{ g}$ of calcium chloride. The highest temperatures recorded were $∘C31.8\ ^{\circ}\text{C}$ , $∘C32.4\ ^{\circ}\text{C}$ , $∘C32.1\ ^{\circ}\text{C}$ , and $∘C32.1\ ^{\circ}\text{C}$ . Calculate the mean highest temperature and the uncertainty (using $±range2\pm \frac{\text{range}}{2}$ ). Express your final answer in the format $mean±uncertainty\text{mean} \pm \text{uncertainty}$ .

[3]

Exothermic and endothermic reactions

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Question 6

Medium

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

Method:

Measure $cm3100\text{ cm}^3$ of water into a polystyrene cup.
Measure the initial temperature of the water.
Add a known mass of calcium chloride to the water.
Stir the mixture until all the calcium chloride has dissolved.
Measure the highest temperature reached by the solution.
Repeat steps 1 to 5 with different masses of calcium chloride.

Table 1: Results of the investigation

Mass of calcium chloride added (g)	Highest temperature of solution ( $∘C^{\circ}\text{C}$ )
$2.0$	$24.0$
$4.0$	$28.0$
$6.0$	$32.0$
$8.0$	$36.0$
$10.0$	$40.0$

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 calcium chloride is exothermic or endothermic, and justify your answer.

[2]

[3]

Exothermic and endothermic reactions

Question 6

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions

Exothermic and endothermic reactions

Question 6

Method:

Table 1: Results of the investigation

Questions:

Exothermic and endothermic reactions Questions