Candidates’ Name: …………………………………..…………………………..…………………..

Signature: …………………..………………………

(Do not write your school / Center name or Number anywhere on this booklet)

545/2

CHEMISTRY

Paper 2 July / Aug 2024 2 ½ HOURS

Uganda Certificate Of Education CHEMISTRY

Paper 2

TIME: 2 hours 30 minutes

CONFIDENTIAL

Great care should be taken that the information given below does not reach the candidates either directly or indirectly.

INSTRUCTIONS FOR PREPARING CHEMICALS AND APPARATUS

The candidates will be allowed to write out a detailed description of the apparatus. The teacher responsible for preparing the apparatus must give details (on the report form attached) about some of the items or apparatus he /she has supplied. The form should be signed by the invigilator, teacher responsible for preparing the apparatus and the Head teacher.

NB: The Head teacher must ensure that the teacher responsible for preparing the apparatus hands in his/ her trial results, properly sealed in a separate envelope and firmly fastened (attached) to the candidates’ scripts envelope(s).

1. The description of the reagents and chemicals specified below does not necessarily correspond with the description in the question paper. Candidates must not be informed of the differences.
2. Candidates are not allowed to use reference books (i.e. text books, booklets on qualitative analysis etc.) during examination.
3. In addition to the fittings and substances ordinarily contained in a chemistry laboratory, each candidate will require:

• 50cm³ measuring cylinder (or 100cm³ measuring cylinder)

• 10cm³ measuring cylinder

• Glass beaker (or Conical flask)

• Stop clock (or Stop watch)

• A thermometer

• 100cm³ of BA2

• 260cm³ of BA1

NB: BA1 is a 0.1M sodium thiosulphate solution BA2 is a 0.05M Hydrochloric acid.

INSTRUCTIONS TO CANDIDATES

This paper consists of one compulsory item.

Answers to this item are to be written in the spaces provided in this booklet.

Use blue or black ink All working must be clearly shown. A Graph paper will be provided

Mathematical tables and silent non-programmable scientific calculators may be used. You are not allowed to use reference books.

Candidates are advised to carefully read the item, make sure they have all the apparatus and chemicals they may need and then plan appropriately before starting.

.

FOR EXAMINER’S USE ONLY

Item 1

In one of the busy photographic processing laboratories in Mbale, the quality and

efficiency of photograph developing solutions are crucial for producing high-quality photographs. The laboratory currently uses a sodium thiosulphate solution in

combination with acids for fixing and stopping photographic development. However, the quality of photographs and processing time varies with the concentration of thiosulphate used in the development process. The Chemistry club of your school have been tasked with conducting a scientific investigation to determine the effect of concentration on the chemical reactions using sodium thiosulphate solution, dilute hydrochloric acid and a number of laboratory materials according to the following

equation;

Na2S2O3 (aq) + 2HCl (aq) ⟶ 2NaCl (aq) + S (s) + H2O (l) + SO2 (g)

You are provided with:

BA1 which is a solution of sodium thiosulphate BA2 which is dilute hydrochloric acid.

Task

As a chemistry learner,

• Plan for an experiment you will carry out to the effect of concentration on rate of reaction between BA1 and BA2

• Conduct the experiment and record your

• Show how you treated your Include ¹

𝑡𝑖𝑚𝑒

and explain your findings.

• Draw conclusion(s) from your investigation

END