Past paper

Form 4 Chemistry national exam 2021 with answers

The 2021 Form 4 national exam paper for Form 4 Chemistry, question by question. Take it timed like the real exam, then see the answer and explanation to every question.

45 questions, 100 marks
120 minutes

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120 minutes, 100 marks. Multiple choice is marked for you; you mark your written answers against the marking points.

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Instructions to candidates

Answer all questions in the ANSWER BOOKLET. Time: 2 hours.

Section A (40 Marks, 2 marks each)

Choose the correct answer from the alternatives given in each question

1
Hydrocarbons are compounds that contain _____
- A.Carbon only
- B.Hydrogen only
- C.Oxygen
- D.Carbon and hydrogen
2 marks
2
The simplest number of alkenes is known as _____
- A.Butane
- B.Ethane
- C.Ethene
- D.Propene
2 marks
3
Which of the following groups has the most reactive non-metals _____
- A.Alkali metals
- B.alkaline metals
- C.halogens
- D.noble gas
2 marks
4
The general formula of alkanes is _____
- A.CnH2n+2
- B.CnH2n
- C.CnH2n+1
- D.CnH2n-1
2 marks
5
Phosphorous-32 has a half-life of 14.3 days. If a sample contains 8.0 mg of phosphoros-32 how many milligrams of phosphorous-32 remains after 42.9 days?
- A.4 mg
- B.6 mg
- C.2.5 mg
- D.1 mg
2 marks
6
_____ is the simplest form of cyclo alkanes
- A.Cyclo butane
- B.cyclo pentane
- C.cyclo propane
- D.cyclo hexane
2 marks
7
According to the general formula of alkenes (CnH2n), the molecular formula of butane is
- A.C4H10
- B.C4H8
- C.C4H12
- D.C4H6
2 marks
8
The hydrophilic part of alcohol is called _____
- A.Alkyl part
- B.hydroxyl part
- C.hydrogen part
- D.carbon part
2 marks
9
The structural formula of ketones is _____
- A.R-O-R
- B.R-C(=O)-R
- C.R-C(=O)-H
- D.R-C(=O)-O-R
2 marks
10
If the number of protons and neutrons in a nucleus are 11, 12 respectively, the nuclear symbol would be:
- A.12/11 X (mass 12, atomic number 11)
- B.11/12 X (mass 11, atomic number 12)
- C.23/11 X (mass 23, atomic number 11)
- D.23/12 X (mass 23, atomic number 12)
2 marks
11
The balance nuclear equation for (11/6 C) that produces a protons is _____
- A.11/6 C -> 1/1 e + 12/7 N
- B.11/6 C -> 0/1 e + 11/5 B
- C.11/6 C -> 0/1 e + 12/7 B
- D.11/6 C -> 0/1 e + 11/7 B
2 marks
12
_____ is the substance that speed up the rate of reaction.
- A.Reactants
- B.Products
- C.Catalyst
- D.Activation energy
2 marks
13
Identify the structure of 2-methyl pentane from the below structures.
- A.CH3-CH2-CH2-CH(CH3)-CH3
- B.CH3-CH(CH3)-CH3
- C.CH3-CH2-CH2-CH2-CH3
- D.CH3-C(CH3)2-CH3
2 marks
14
Which of the following structures is saturated:
- A.CH=CH3
- B.CH=CH-CH3
- C.CH3-CH3
- D.CH3-CH2-C=CH
2 marks
15
Which of the following figures indicates 2-methylphenol;
- A.Figure a (CH3 next to OH)
- B.Figure b
- C.Figure c (CH3 opposite OH)
- D.Figure d
2 marks
16
The functional group that contains both aldehyde and ketone is known as _____
- A.Aldehyde group
- B.ketone group
- C.carbonyl group
- D.amino group
2 marks
17
When one large nucleus splits into two smaller nucleus, this nuclear reaction is known as
- A.Fusion reaction
- B.fission reaction
- C.ionizing radiation
- D.alpha decay
2 marks
18
Example of monosaccharide that contains five carbon (pentose) is _____
- A.Erythrose
- B.ribose
- C.galactose
- D.cellulose
2 marks
19
Which of the following is homogeneous chemical equilibrium
- A.CO2(g) + C(s) <=> 2CO(g)
- B.CaCO3(s) <=> CaO + CO2
- C.P4(s) + 6Cl2(g) <=> 4PCl3
- D.N2 + O2 <=> 2NO(g)
2 marks
20
Le Chatelier's principle states that if one or more factors disturb equilibrium, the position of equilibrium will shift in order to _____ the change.
- A.Oxidize
- B.increase
- C.induce
- D.reduce
2 marks

Section B (10 Marks, 1 mark each)

Fill in the empty blank with suitable word from the box below

B1
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The general structure of organic acid is _____
1 mark
B2
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The alcohol that contain two hydroxyl group is called _____ alcohol.
1 mark
B3
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): Amino acids in the proteins are joined together by _____ bond
1 mark
B4
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The general formula of alkyne is _____
1 mark
B5
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The building unit of triglycerides is glycerol and _____ acids
1 mark
B6
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): _____ equilibrium is a state in which the rates of the forward and reverse reactions are equal.
1 mark
B7
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The chemical constituents of the living system are called _____
1 mark
B8
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): The radioactive decay which carry positive charge is known as _____ particles
1 mark
B9
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): In equilibrium constant expression, if the value of Kc is greater than one (Kc > 1), this reaction is said to be _____ favoured.
1 mark
B10
Fill in the empty blank with suitable word from the box (Isomers, Biomolecules, CnH2n-2, Dihydroxy, Peptide, R-COOH, Fatty, Chemical, Product, Alpha): _____ are molecules with the same molecular formula but different structural formula.
1 mark

Section C (50 marks): Answer all questions in the section

C1a
a) What does IUPAC stands for? (2 mark)
2 marks
C1b-a
b) Give IUPAC names to the following organic molecules (4 marks): a) CH3-CH(CH3)-CH2-CH3
1 mark
C1b-b
b) Give IUPAC names to the following organic molecules (4 marks): b) CH3-CH=CH-CH(Br)-CH(CH3)-CH3
1 mark
C1b-c
b) Give IUPAC names to the following organic molecules (4 marks): c) CH3-CH(Cl)-CH2-OH
1 mark
C1b-d
b) Give IUPAC names to the following organic molecules (4 marks): d) CH3-CH2-C(=O)-H
1 mark
C2
Phenols are hydroxyl derivatives of benzene that have aromas smell, state three uses of phenols. (3 Marks)
3 marks
C3
Draw the possible structural formula for isomers of pentane using the following formula (2^(n-4) + 1). (3 marks)
3 marks
C4a
Define: a. The term biochemistry? (2 mark)
2 marks
C4b
b. Briefly explain the major types of biochemistry. (5 marks)
5 marks
C5
Calculate the equilibrium constant (Kc), if the equilibrium concentrations are as follows: PCl5 (g) <=> PCl3 (g) + Cl2 (g). [PCl5] = 0.0096M, [PCl3] = 0.0247M, and [Cl2] = 0.0247M. (6 marks)
6 marks
C6
The half-life of polonium-210 is 138.4 days, how many milligrams (mg) of polonium-210 remain after 415.2 day if you start with 2.0 mg of polonium-210? (5 marks)
5 marks
C7
The rate of chemical reaction increases with increase in the presence of catalyst, explain. (5 marks)
5 marks
C8
Distinguish between ionizing and non-ionizing radiation. (5 marks)
5 marks
C9
A radioactive isotope of 38/19 K, emits a radioactive emission and changes into 36/18 Ar. Synthesize the balanced equation of this nuclear reaction (5 marks)
5 marks
C10
Show the electron configuration of fluorine (9F) and chlorine (17Cl) (5 marks)
5 marks

Paper set by the Federal Ministry of Education, Culture and Higher Education (MoECHE), Somalia. Shared free of charge to help students prepare. The answers and explanations are written by Sheerxirfad teachers.

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