IGCSE Chemistry 0620 Paper 62, Oct/Nov 2023

Name the apparatus used to grind the seashell to form a powder in step 1.

Explain why it is important that the dilute hydrochloric acid is in excess in step 3.

Name the items of apparatus labelled A and B in Fig. 1.2. A ................................................................................................................................................ B ................................................................................................................................................

The residue obtained in step 4 is not pure. Identify one substance, other than water, that is in the residue and prevents it from being pure.

The student washes the residue. Describe two additional steps the student must now take to find the percentage of silicon(IV) oxide in the seashell.

Use the description of the experiments and the thermometer diagrams to complete Table 2.1.

Add a suitable scale to the y-axis in Fig. 2.1. Your scale should extend by $2{}^{\circ }\mathrm{C}$ above your highest temperature in Table 2.1. Plot your results from Experiments 1 to 6 on the grid. Draw two straight lines through your points, one through the first three points and one through the last three points. Extend your straight lines so that they cross.

The point on the graph where the two straight lines cross is where all of the aqueous sodium hydroxide reacts with all of the dilute hydrochloric acid to form a neutral solution. Use your graph in Fig. 2.1 to deduce the volume of dilute hydrochloric acid and the volume of aqueous sodium hydroxide that react together to produce a neutral solution. Show your working on Fig. 2.1. volume of dilute hydrochloric acid = .............................. ${\mathrm{c}\mathrm{m}}^3$ volume of aqueous sodium hydroxide = .............................. ${\mathrm{c}\mathrm{m}}^3$

Predict the pH of the solution in the boiling tube when the volumes in (c)(i) are mixed together. pH = ..............................

Deduce which solution, dilute hydrochloric acid or aqueous sodium hydroxide, is the most concentrated. Use your answer to (c)(i) to explain why. most concentrated solution ................................................................................................. explanation ......................................................................................................................... .............................................................................................................................................

State how the pH and temperature recorded in each experiment would differ, if at all, if a polystyrene cup is used in place of the boiling tube. Explain any differences. pH .............................................................................................................................................. temperature ............................................................................................................................... explanation ................................................................................................................................ ....................................................................................................................................................

The volumes of the solutions used in these experiments were measured using a burette. Explain why a volumetric pipette could not be used instead of a burette in this experiment.

Tests on solid K The student dissolves solid K in water to form solution K. The student divides solution K into four portions. Table 3.1 shows the tests and the student’s observations for solution K. Identify two cations that test 1 shows could be in solid K.

Describe an additional test that could be carried out on solution K to confirm which of the two cations you have identified in (a)(i) is in solid K. Explain how the test will show which of these two cations is in solid K. test ...................................................................................................................................... explanation ......................................................................................................................... .............................................................................................................................................

Identify the anion in solid K.

Tests on solid L Solid L is barium nitrate. Complete the expected observations. The student carries out a flame test on solid L. observations ........................................................................................................................

The student dissolves the remaining solid L in water to form solution L. The student divides solution L into three portions. To the first portion of solution L, the student adds a piece of aluminium foil and $5{\mathrm{c}\mathrm{m}}^3$ of aqueous sodium hydroxide and warms the mixture. The student tests for any gas produced. observations .............................................................................................................................. ..............................................................................................................................................

To the second portion of solution L, the student adds $1{\mathrm{c}\mathrm{m}}^3$ of dilute nitric acid and a few drops of aqueous silver nitrate. observations .............................................................................................................................. ..............................................................................................................................................

To the third portion of solution L, the student adds $1{\mathrm{c}\mathrm{m}}^3$ of dilute sulfuric acid. observations .............................................................................................................................. ..............................................................................................................................................