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Form 4 Chemistry Paper 1 2023 Joint Exam

Published on October 5th 2023 | 2 mins , 374 words

1. Use the diagram below to answer the questions that follow


(a)In which set-up will the iron nail rust? Explain.

Q. Copper is less reactive than iron, hence iron reacts with oxygen and moisture leading to the formation of rust (hydrated Iron (III) Oxide). This method of preventing rusting is known as sacrificial protection


In everyday scenarios, Configuration A involves storing a metal that ranks higher than iron in the reactivity series alongside iron to prevent rusting or corrosion. 

Other methods used to prevent rusting include:

Galvanizing: refers to coating of iron metal with zinc during manufacturing.  Galvanization involves coating iron or steel with a layer of zinc to protect it from corrosion. This is usually done through a process called hot-dip galvanizing, where the steel is immersed in molten zinc 

Oiling: Oil forms a protective barrier that helps prevent exposure of iron metal to moisture and oxygen, the two primary factors contributing to the corrosion of iron. The oil coating acts as a physical barrier, inhibiting the direct contact between the iron and the surrounding environment. 

(b) State one advantage of rusting

  • The oxide formed prevent the metal underneath from further corrosion by providing a protective layer

2. During an investigation to identify illegal steroids used by three athletes, urine samples were obtained and labelled as A, B and C. Illegal steroid was labelled as X, each urine sample had two components each and A and C contain the illegal steroid. 

(a) Give the name of the process used to identify the illegal steroids in athletes

  • Chromatography 

(b) Draw a chromatogram showing the information given above


3. The  flowchart below shows the process that can be used to obtain substance C from ammonia gas when it is heated to about \(900^{\circ}C\) in air and in the presence of a catalyst


(a) Ammonia is obtained in large scale by Haber process. Name the raw materials A and B (1mk)

  • Nitrogen
  • Hydrogen

(b) Name the substance C and the catalyst used (1mk)

  • Substance C: Nitrogen (II) Oxide // NO
  •  Vanadium(V) oxide (V₂O₅) 

(c) Write an equation to show the product formed when C is cooled in the presence of air

\(2NO_{(g)}\) + \(O_{2(g)}\)  \(\rightarrow\) \(2NO_{2(g)}\)

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