JAMB Past Questions and Answers - Page 1253

6,261.

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.

6,262.

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

6,263.

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

6,264.

Hydrogen diffused through a porous plug

A.

thrice as fast as oxygen

B.

at the same speed as oxygen

C.

four times as fast as oxygen

D.

twice as fast as oxygen

Correct answer is C

Using Graham's Law of Diffusion,

\(\frac{R_1}{R_2} = \sqrt{\frac{m_2}{m_1}}\)

\(\frac{R_H}{R_O} = \sqrt{\frac{m_O}{m_H}}\)

\(\frac{R_H}{R_O} = \sqrt{\frac{32}{2}}\)

\(\frac{R_H}{R_O} = \sqrt{16} = 4\)

\(\therefore R_H = 4 \times R_O\)

Therefore, hydrogen diffuses 4 times faster than oxygen.

6,265.

The emission of two successive beta particles from the nucleus \(^{32} _{15} P\) will produce

A.

\(^{30} _{14}\)Si

B.

\(^{32} _{13}\)Al

C.

\(^{32} _{17}\)Cl

D.

\(^{32} _{16}\)S

Correct answer is C

\(^{32} _{15}\)P \(\to\) 2\(^{0} _{-1}\)e + \(^{a} _{b}\)X

32 = 2(0) + a

a = 32

15 = 2(-1) + b

b = 15 + 2

b = 17

\(\therefore\) \(^{a} _{b}\)X = \(^{32} _{17}\)Cl