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Chemistry Past Questions

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80 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

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Past Questions

80 questions

Question 1 of 20 80 total questions

Question 21

jamb 2019

Consider the equation below:

Cr\(_2\)O\(_7 ^{2-}\) + 6Fe\(^{2+}\) + 14H\(^{+}\) \(\to\) 2Cr\(^{3+}\) + 6Fe\(^{3+}\) + 7H\(_2\)O.

The oxidation number of chromium changes from

A+5 to +3

B+6 to +3

C-2 to +3

D+7 to +3

View Explanation & Discuss

Question 22

jamb 2019

Which of the following pairs cannot be represented with a chemical formula?

Aair and bronze

Bbronze and sodium chloride

Ccopper and sodium chloride

Dcaustic soda and washing soda

View Explanation & Discuss

Question 23

jamb 2019

Which of the following describes the chemical property of acids?

ANone of the above

BAcid + XCO\(_3\) \(\to\) Salt + H\(_2\)O + NH\(_3\)

CAcid + NaOH \(\to\) Normal salt + CO\(_2\)

DAcid + X\(_n\)CO\(_3\) \(\to\) Salt + H\(_2\)O + CO\(_2\)

View Explanation & Discuss

Question 24

jamb 2019

Which of the following pollutants will lead to the depletion of ozone layer?

Achlorofluorocarbon

Bcarbon (ii) oxide

Chydrogen sulphide

Dsulphur (iv) oxide

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Question 25

jamb 2019

Which two gases can be used for the demonstration of the fountain experiment?

ASO\(_4\) and NH\(_3\)

BSO\(_3\) and NH\(_3\)

CHCl and NH\(_3\)

DSO\(_2\) and CO

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Question 26

jamb 2019

A radioactive nucleus has a half-life of 20 years, starting with 100,000 particles, how many particles will be left exactly at the end of 40 years

A75,000 particles

B35,000 particles

C25,000 particles

D50,000 particles

View Explanation & Discuss

Question 27

jamb 2019

Na\(_2\)CO\(_3\) + 2HCl \(\to\) 2NaCl + H\(_2\)O + CO\(_2\)

The indicator most suitable for this reaction should have a pH equal to

View Explanation & Discuss

Question 28

jamb 2019

The molecular shape and bond angle of water are respectively

Alinear, 180°

Bbent, 109.5°

Ctetrahedral, 109.5°

Dbent, 105°

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Question 29

jamb 2019

Which of the following properties increases from left to right along the period but decreases down the group in the Periodic Table?
i. Atomic Number ii. Ionization energy iii. Metallic character iv. Electron affinity

Aii and iii only

Bii and iv only

Ciii and iv only

Di and ii only

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Question 30

jamb 2019

At 27°C, 58.5g of sodium chloride is present in 250cm\(^3\) of a solution. The solubility of sodium chloride at this temperature is?
(molar mass of sodium chloride = 111.0gmol\(^{-1}\))

A2.0 moldm\(^{-3}\)

B0.25 moldm\(^{-3}\)

C1.0 moldm\(^{-3}\)

D0.5 moldm\(^{-3}\)

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Question 31

jamb 2019

What technique is suitable for separating a binary solution of potassium chloride and potassium trioxochlorate (V)?

AFractional crystallization

BFractional distillation

CFiltration

DEvaporation

View Explanation & Discuss

Question 32

jamb 2019

Which of the following does not support the fact that air is a mixture?

Athe constituents of air are in a fixed proportion by mass

Bit cannot be represented with a chemical formula

Cthe constituents of air can be separated by physical by physical means

Dnone of the above

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Question 33

jamb 2019

Which of the following statements about catalyst is false?

Abiological catalysts are called enzymes

Bcatalyst do not appear in the balanced equation

Ccatalyst reduce the activation energy for a reaction

Dcatalysts do not alter the mechanism of the reaction and never appear in the rate low

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Question 34

jamb 2019

The heat of formation of ethene, C\(_2\)H\(_4\) is 50 kJmol\(^{-1}\), and that of ethane, C\(_2\)H\(_6\) is -82kJmol\(^{-1}\). Calculate the heat evolved in the process:

C\(_2\)H\(_4\) + H\(_2\) \(\to\) C\(_2\)H\(_6\)

A-122kJ

B-132kJ

C-88kJ

D-60kJ

View Explanation & Discuss

Question 35

jamb 2019

If acidified Potassium Dichromate(VI) (K\(_2\)Cr\(_2\)O\(_7\)) acts as oxidizing agent, color changes from

Ayellow to green

Borange to green

Cyellow to red

Dorange to red

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Question 36

jamb 2019

Which of the following reactions is an oxidation process?

A2H\(^+\) + 2e\(^-\) \(\to\) H\(_2\)

B2O\(^{2-}\) + 4e\(^-\) \(\to\) O\(_2\)

COCl\(^-\) + H\(_2\)O + 2e\(^-\) \(\to\) 2OH\(^-\) + Cl\(^-\)

DCl + e\(^-\) \(\to\) Cl\(^-\)

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Question 37

jamb 2019

For the general equation of the nature
xP + yQ ⇌ mR + nS, the expression for the equilibrium constant is

Ak[P]\(^x\)[Q]\(^y\)

B\(\frac{m[R][S]}{x[P]y[Q]}\)

C\(\frac{[P]^x[Q]^y}{[R]^m[S]^n}\)

D\(\frac{[R]^m[S]^n}{[P]^x[Q]^y}\)

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Question 38

jamb 2019

Consider the reaction
A\(_{(s)}\) + 2B\(_{(g)}\) → 2C\(_{(aq)}\) + D\(_{(g)}\)
What will be the effect of a decrease in pressure on the reaction?

Athe equilibrium will shift

Brate of forward reaction will increase

Crate of backward reaction will increase

Drates of forward and backward reaction are not affected

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Question 39

jamb 2019

Which of the following represents the kind of bonding present in ammonium chloride?

Aionic only

Bcovalent only

Cionic and covalent

Ddative covalent

View Explanation & Discuss

Question 40

jamb 2019

When ammonia and hydrogen ion bond together to form ammonium ion, the bond formed is called

Aelectrovalent bond

Bcompound bond

Cionic bond

Dcovalent bond

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