JAMB Chemistry Past Questions 2013

10 questions from the JAMB 2013 Chemistry paper, with answers and explanations. Tap "Show answer" under each one when you are ready.

JAMB 2013Question 1 · Acids, Bases, and Salts

Three drops of a

1.0 mol d m^{- 3}

solution of HCl was added to

20 c m^{3}

of a solution of pH6.4. The pH of the resulting solution will be

A.close to that of pure water
B.less than 6.4
C.greater than 6.4
D.unaltered

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Answer: B. less than 6.4

Adding a strong acid (HCl) to the solution increases the $H^{+}$ concentration, lowering the pH below 6.4.

JAMB 2013Question 2 · Atomic Structure and Chemical Bonding

The shape of the carbon (lV) oxide molecule is

A.pyramidal
B.linear
C.angular
D.tetrahedral

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Answer: B. linear

Carbon(IV) oxide, $C O_{2}$ , is a linear molecule (O=C=O).

JAMB 2013Question 3 · Chemistry of Metals

A metal that forms soluble trioxosulphate (IV) ion is

A.barium
B.potassium
C.manganese
D.aluminium

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Answer: B. potassium

Potassium, a Group 1 metal, forms a soluble trioxosulphate(IV) salt, unlike many trioxosulphate(IV) salts of other metals.

JAMB 2013Question 4 · Chemistry of Non-metals and Gases

The constituent of air that acts as a diluent is

A.nitrogen
B.carbon (IV) oxide
C.noble gases
D.oxygen

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Answer: A. nitrogen

Nitrogen makes up about 78% of air and acts mainly as a diluent, moderating the reactivity of oxygen.

JAMB 2013Question 5 · Chemistry of Non-metals and Gases

Which of the gases is employed as an anaesthesia?

A. $N_{2} O$
B. $N O_{2}$
C. $N H_{3}$
D.NO

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Answer: A. $N_{2} O$

Nitrogen(I) oxide $(N_{2} O)$ , or 'laughing gas', is used as an anaesthetic.

JAMB 2013Question 6 · Electrochemistry and Redox Reactions

Zn (s)

CuS O_{4} (aq)

\to

ZnS O_{4} (aq)

Cu (s)

In the reaction above, the oxidizing agent is

A. $CuS O_{4} (aq)$
B. $ZnS O_{4} (aq)$
C. $Cu (s)$
D. $Zn (s)$

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Answer: A. $CuS O_{4} (aq)$

$CuS O_{4}$ supplies $C u^{2 +}$ which is reduced to Cu while oxidizing Zn, making $CuS O_{4} (aq)$ the oxidizing agent.

JAMB 2013Question 7 · Environmental and Industrial Chemistry

The radioactive emission with the least ionization power is

A. $α - p a r t i c l es$
B.X-rays
C. $γ - r a y s$
D. $β - r a y s$

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Answer: C. $γ - r a y s$

Gamma rays, being highly penetrating with weak interaction with matter, have the least ionizing power among common radioactive emissions.

JAMB 2013Question 8 · Organic Chemistry

The decarboxylation of ethanoic acid will produce carbon (IV)oxide and

A.methane
B.ethane
C.propane
D.butane

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Answer: A. methane

Decarboxylation of ethanoic acid $(C H_{3} COOH)$ removes the -COOH group as $C O_{2}$ , leaving methane $(C H_{4})$ .

JAMB 2013Question 9 · Physical Chemistry

An example of a hygroscopic substance is

A.CuO (S).
B.MgCL 2(S).
C.CaCL 2(S).
D.NaOH (S).

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Answer: C. CaCL 2(S).

Calcium chloride, $CaC l_{2} (s)$ , is hygroscopic and commonly used as a drying agent.

JAMB 2013Question 10 · Physical Chemistry

2S O_{2} (g)

O_{2} (g)

⟺

2S O_{3} (g)

△ H = - 395.7 k J m o l^{- 1}

In the reaction above, the concentration of

2S O_{3} (g)

can be in creased by

A.decreasing the pressure
B.decreasing the temperature
C.the addition of catalyst
D.increasing the temperature

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Answer: B. decreasing the temperature

Since the forward reaction is exothermic, lowering the temperature shifts the equilibrium further towards $S O_{3}$ , increasing its concentration.

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JAMB Chemistry Past Questions 2013

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