JAMB Chemistry Past Questions & Answers - Page 42

206.

A solution X, on mixing with AgNO\(_3\) solution gives a white precipitate soluble in aqueous NH\(_3\), a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain

A.

Al\(^{3+}\), Cl\(^-\)

B.

Hg\(^+\), SO\(_4 ^{2-}\)

C.

Pb\(^{2+}\), Cl\(^-\)

D.

Ag\(^+\), SO\(_4 ^{2-}\)

Correct answer is C

No explanation has been provided for this answer.

207.

The reaction \(2H_2 S + SO_2 \to 3S + 2H_2 O\) is

A.

not a redox reaction because there is no oxidant in the reaction

B.

not a redox reaction because there is no reductant in the reaction

C.

a redox reaction in which H\(_2\)S is the oxidant and SO\(_2\) is the reductant

D.

a redox reaction in which SO\(_2\) is the oxidant and H\(_2\)S is the reductant

Correct answer is D

No explanation has been provided for this answer.

208.

How many alkoxyalkanes can be obtained from the molecular formula C\(_4\)H\(_{10}\)O?

A.

4

B.

2

C.

1

D.

3

Correct answer is D

No explanation has been provided for this answer.

209.

The cost of discharging 6.0g of a divalent metal, X from its salt is ₦12.00. What is the cost of discharging 9.0g of a trivalent metal, Y from its salt under the same condition?
[X = 63, Y = 27, 1F = 96,500C]

A.

N12.00

B.

N27.00

C.

N63.00

D.

N95.00

Correct answer is C

For X:  X\(^{2+}\) + 2e\(^-\) \(\to\) X

2F = 63g

xF = 6g

x = \(\frac{6 \times 2}{63} = \frac{4}{21} F\)

\(\frac{4}{21}\)F = N12.00

1F = \(\frac{12}{\frac{4}{21}}\)

= N63.00

1F is equivalent to N63.00.

For Y: Y\(^{3+}\) + 3e\(^-\) \(\to\) Y

3F = 27g 

xF = 9g

x = \(\frac{3 \times 9}{27}\)

= 1F

1F = N63.00

210.

If the cost of electricity required to discharge 10g of an ion X\(^{3+}\) is N20.00, how much would it cost to discharge 6g of ion Y\(^{2+}\)?

[1 faraday = 96,500C, atomic masses are X = 27, Y = 24]

A.

N10.00

B.

N6.00

C.

N20.00

D.

N9.00

Correct answer is D

X\(^{3+}\) + 3e\(^-\) \(\to\) X

3F = 27g

xF = 10g

\(\frac{x}{3} = \frac{10}{27} \implies x = \frac{10}{9} F\)

\(\frac{10}{9}\)F \(\equiv\) N20.00

1F is equivalent to x

\(\frac{1}{\frac{10}{9}} = \frac{x}{20}\)

\(\frac{9}{10} = \frac{x}{20} \implies x = N18.00\)

1F is equivalent to N18.00.

Y\(^{2+}\) + 2e\(^-\) \(\to\) Y

2F = 24g

xF = 6g

x = \(\frac{6 \times 2}{24} = \frac{1}{2} F\)

1F = N18.00

\(\frac{1}{2}\)F = \(\frac{1}{2} \times N18.00\)

= N9.00