O Level Chemistry 5070 Paper 41, Oct/Nov 2023

Name apparatus X.

The student has incorrectly positioned the delivery tube in the apparatus shown in Fig. 1.1. Complete Fig. 1.2 to show: • the correct position of the delivery tube • the rest of the apparatus the student uses to collect and measure the volume of gas produced.

The student collects $48.0{\text{ cm}}^3$ of carbon dioxide during the first 2 minutes. Calculate the mean rate of reaction, in ${\text{cm}}^3\mathrm{/}\text{s}$, during the first 2 minutes.

Complete Table 2.1 by filling in the three missing values.

Parts of the thermometer used in Experiment 5 are shown in Fig. 2.1. The liquid levels inside the thermometer are missing. Complete Fig. 2.1 by drawing in the liquid level to show: • the initial temperature of $\mathbf{P}$ in Experiment 5 • the highest temperature reached in Experiment 5.

Draw a graph of temperature rise against volume of $\mathbf{Q}$ on the grid in Fig. 2.2. You should: • plot the point (0,0) as there is no temperature rise when no $\mathbf{Q}$ is added • plot the temperature rises and volumes of $\mathbf{Q}$ from Table 2.1 • draw a straight line of best fit for the first four points • draw a straight line of best fit for the last three points • extend the lines so that they intersect.

The point where the two lines intersect indicates the volume of $\mathbf{Q}$ that exactly neutralises $25.0{\text{ cm}}^3$ of $\mathbf{P}$. Determine the volume of $\mathbf{Q}$ where the two lines on the graph intersect.

$\mathbf{Q}$ is $2.24\text{ mol}\mathrm{/}{\text{dm}}^3$ hydrochloric acid. Use your answer to (d) to calculate the concentration of potassium hydroxide in $\mathbf{P}$. $$\mathrm{K}\mathrm{O}\mathrm{H}+\mathrm{H}\mathrm{C}\mathrm{l}\to \mathrm{K}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}$$

A measuring cylinder is used to measure the volumes of water. Suggest why the volumes of water in Table 2.1 are not given to one decimal place.

State and explain why a plastic cup rather than a metal cup is used in these experiments.

State why the mixture is stirred before measuring the temperature in these experiments.

Part of the method for test 1 is missing. Describe the missing part of the method that is needed to give the observations shown.

The observations for test 1 are incomplete. State one other observation which is made for test 1.

Suggest why the ammonia produced in test 2 has no effect on the litmus paper.

Solution $\mathbf{X}$ contains two cations. Identify the cation in solution $\mathbf{X}$ which produces ammonia in test 2.

Explain why the student cannot identify the second cation in solution $\mathbf{X}$ from the tests and observations in Table 3.1.

Identify the anion in $\mathbf{X}$.

The student adds universal indicator to solution $\mathbf{Y}$ in a test-tube. The universal indicator turns red. Identify the cation present in $\mathbf{Y}$.

The student adds a piece of magnesium ribbon to $\mathbf{Y}$. Hydrogen is produced. Suggest two observations the student makes.

Describe how the student tests the gas to show that it is hydrogen. test .................................................................................................................................... observation if hydrogen present ........................................................................................

The student adds dilute nitric acid and then adds aqueous silver nitrate to $\mathbf{Y}$. A white precipitate is observed. Identify the anion present in $\mathbf{Y}$.

Identify $\mathbf{Y}$.