JAMB Chemistry Past Questions 2017

10 questions from the JAMB 2017 Chemistry paper, with answers and explanations. Tap "Show answer" under each one when you are ready.

JAMB 2017Question 1 · Acids, Bases, and Salts

A sample of orange juice is found to have a PH of 3.80. What is the concentration of the hydroxide ion in the juice?

A.1.6 $\times$ 10 -4
B.6.3 $\times$ 10 -11
C.6.3 $\times$ 10 -4
D.1.6 $\times$ 10 -11

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Answer: B. 6.3 $\times$ 10 -11

pOH = 14 - pH = 14-3.80 = 10.2. [ $O H^{-}$ ] = $1 0^{-} 10.2$ = $6.3 \times 1 0^{- 11}$ mol/dm3.

JAMB 2017Question 2 · Atomic Structure and Chemical Bonding

The shape of ammonia molecules is

A.trigonal pyramidal
B.octahedral
C.square planar
D.tetrahedral

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Answer: A. trigonal pyramidal

The ammonia molecule $(N H_{3})$ has a trigonal pyramidal shape due to its one lone pair.

JAMB 2017Question 3 · Chemistry of Metals

The reddish–brown rust on iron roofing sheets consists of

A. $F e^{3 +} (H_{2} O)_{6}$
B. $FeO \cdot H_{2} O$
C. $F e_{2} O_{3} \cdot x H_{2} O$
D. $F e_{3} O_{4} \cdot 2 H_{2} O$

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Answer: C. $F e_{2} O_{3} \cdot x H_{2} O$

Rust is hydrated iron(III) oxide, $F e_{2} O_{3} \cdot x H_{2} O$ .

JAMB 2017Question 4 · Chemistry of Non-metals and Gases

A given mass of gas occupies

2 d m^{3}

at 300k. At what temperature will its volume be doubled, keeping the pressure constant?

A.400k
B.480k
C.550k
D.600k

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Answer: D. 600k

By Charles' law, $V_{1}$ /T1 = $V_{2}$ /T2: T2 = T1 x ( $V_{2}$ / $V_{1}$ ) = 300 x 2 = $600 K$ .

JAMB 2017Question 5 · Chemistry of Non-metals and Gases

In the laboratory preparation of trioxonitrate (V) acid the nitrogen(iv) oxide formed as a by-product is removed by

A.further heating
B.adding concentrated $H_{2} S O_{4}$
C.cooling the acid solution with cold water
D.bubbling air through the acid solution

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Answer: D. bubbling air through the acid solution

Dissolved $N O_{2}$ by-product in the nitric acid solution is removed by bubbling air through it, which oxidizes/expels the $N O_{2}$ .

JAMB 2017Question 6 · Electrochemistry and Redox Reactions

What mass of silver is deposited when a current of

10 A

passes through a silver-salt solution for

4, 830 s

? [Ag = 108;

F = 96, 500 C mo l^{- 1}

]

A. $54.0 g$
B. $27.0 g$
C. $13.5 g$
D. $108.0 g$

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Answer: A. $54.0 g$

Q = It = 10x4830 = $48300 C$ . Moles electrons = $\frac{48300}{96500}$ = $0.5 mol$ . Since $A g^{+}$ + e- → Ag, moles Ag = $0.5 mol$ ; mass = 0.5x108 = $54.0 g$ .

JAMB 2017Question 7 · Environmental and Industrial Chemistry

Aluminium hydroxide is used in the dyeing industry as a

A.dye
B.dispersant
C.salt
D.mordant

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Answer: D. mordant

Aluminium hydroxide is used in dyeing as a mordant, helping dyes bind to fabric fibres.

JAMB 2017Question 8 · Organic Chemistry

The general formula of alkanones is

A.RCHO
B.RCOR'
C.RCOOH
D.RCOOR

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Answer: B. RCOR'

Alkanones (ketones) have the general formula RCOR'.

JAMB 2017Question 9 · Organic Chemistry

Incomplete oxidation of ethanol yields

A. $C H_{3} COOH$
B. $C H_{3} COC H_{3}$
C. $C H_{3} C H_{2} OC H_{2} C H_{3}$
D. $C H_{3} CHO$

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Answer: D. $C H_{3} CHO$

Incomplete (partial) oxidation of a primary alkanol like ethanol gives the aldehyde, $C H_{3} CHO$ , before further oxidation to the acid.

JAMB 2017Question 10 · Organic Chemistry

Ethene is prepared industrially by

A.Reforming
B.Polymerization
C.Distillation
D.Cracking

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Answer: D. Cracking

Ethene is industrially produced by cracking larger hydrocarbon fractions (e.g. naphtha) from crude oil.

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