CSEC Chemistry Paper 3 May/June 2025 - Free CXC Past Paper with Answers

(i) Complete Table 1.

TABLE 1: HEAT OF NEUTRALIZATION EXPERIMENT BETWEEN POTASSIUM HYDROXIDE AND DILUTE SULFURIC ACID

Volume of Solution X $(\text{cm}^3)$	Volume of Solution Y $(\text{cm}^3)$

Write a balanced chemical equation for the reaction between sulfuric acid and potassium hydroxide.

Use the data from Table 1 to plot a graph of temperature rise against the volume of Solution X using the axes provided in Figure 1 on page 7. Draw TWO best fit intersecting straight lines.

From the graph drawn in (b), determine the largest temperature rise, $\Delta T$ , and the corresponding volume of Solution X needed to cause this temperature rise.

(i) $\Delta T = \text{____________________________________________________________________ }^\circ\text{C}$ (ii) Volume of Solution X = $\text{____________________________________________________________________ cm}^3$

Calculate the heat change at the point of neutralization for the reaction between sulfuric acid and potassium hydroxide.

[Use $\Delta H = m \times c \times \Delta T$ . Note: The specific heat capacity of the solution is $4.2 \text{ J/g}^\circ\text{C}$ . Assume that the density of the solution is $1 \text{ g/cm}^3$ .]

Calculate the number of moles of sulfuric acid used in the experiment.

Calculate the enthalpy change ( $\Delta H$ ) for the reaction between sulfuric acid and potassium hydroxide. Include an appropriate sign for $\Delta H$ .

State ONE source of error in the experiment.

State ONE precaution that should be taken with this experiment.

A student conducted the following tests on Solution C and Solution D. The inferences made are recorded in Table 2. Complete Table 2 to show all observations.

TABLE 2: RESULTS OF TESTS CONDUCTED ON SOLUTION C AND SOLUTION D

TEST	OBSERVATION	INFERENCE
(a) To a portion of Solution C, aqueous sodium hydroxide is added dropwise until in excess and then heated. The gas evolved is tested with moist red litmus paper.		$\text{NH}_4^+$ , $\text{Na}^+$ or $\text{K}^+$ ions present
		Confirms $\text{NH}_4^+$ ions present
(b) To another portion of Solution C, dilute nitric acid is followed by dropwise addition of silver nitrate.		$\text{Cl}^-$ ions present
(c) To a portion of Solution D, aqueous sodium hydroxide is added until in excess.		$\text{Al}^{3+}$ , $\text{Pb}^{2+}$ or $\text{Zn}^{2+}$ ions present
(d) To another portion of Solution D, aqueous ammonia is added dropwise until in excess.		$\text{Al}^{3+}$ or $\text{Pb}^{2+}$ ions present
(e) To another portion of Solution D, aqueous potassium iodide is added.		$\text{Pb}^{2+}$ ions absent and $\text{Al}^{3+}$ ions present

InkFill and FineInk are two competing ink manufacturing companies. InkFill claims that its water soluble brown ink is richer in colour than FineInk's water soluble brown ink. You have been hired as an independent consultant to determine whether InkFill's claim is true.

Plan and design an experiment to determine whether InkFill's claim is true. The hypothesis is given below.

Hypothesis: The 'richer' brown ink contains more components.

Complete your plan and design under the following headings.

Apparatus and Materials

Draw a labelled diagram of the experiment set-up.

Data to be Collected

Discussion as it relates to the Hypothesis

15	35
25	25
35	15
45	5

CSEC Chemistry Paper 3 May/June 2025 Questions

Question 1 (26 marks)

Question 2 (10 marks)

Question 3 (12 marks)