JAMB Chemistry Past Questions & Answers - Page 57

281.

2-methylprop-1-ene is an isomer of?

A.

3-methyl but-1-ene

B.

2-methyl but-1-ene

C.

but-2-ene

D.

pent-2-ene

Correct answer is C

somers of Butene: are But-1-ene, But-2-ene, 2-Methylpropene / 2-methylprop-1-ene

282.

A certain hydrocarbon on complete combustion at s.t.p produced 89.6dm\(^3\) of CO\(_2\) and 54g of water. The hydrocarbon should be?

A.

C\(_6\)H\(_6\)

B.

C\(_4\)H\(_{10}\)

C.

C\(_5\)H\(_{10}\)

D.

C\(_4\)H\(_6\)

Correct answer is D

C\(_x\)H\(_y\) + (x + y/4)O\(_2\) \(\to\) x CO\(_2\) + y/2 H\(_2\)O

89.6 dm\(^3\) \(\to\) x moles CO\(_2\)

22.4 dm\(^3\) \(\to\) 1 mole CO\(_2\)

x = \(\frac{89.6}{22.4}\)

= 4 moles CO\(_2\)

54g of H\(_2\)O \(\to\) k moles H\(_2\)O

18g H\(_2\)O \(\to\) 1 mole H\(_2\)O

k = \(\frac{54}{18}\)

= 3 moles H\(_2\)O

From the equation above,

x = 4 

k = y/2 = 3

y/2 = 3 \(\implies\) y = 6

\(\therefore\) The hydrocarbon C\(_x\)H\(_y\) = C\(_4\)H\(_6\)

283.

The IUPAC name for CH\(_3\)CH\(_2\)COOCH\(_2\)CH\(_3\) is

A.

methylpropanoate

B.

ethylethanoate

C.

ethylpropanoate

D.

methylethanoate

Correct answer is C

No explanation has been provided for this answer.

284.

The number of Hydrogen ions in 1.0\(dm^{3}\) of 0.02\(moldm^{-3}\) tetraoxosulphate(VI) acid is   \([N_{A} = 6.02 \times 10^{23}]\)

A.

\(1.2 \times 10^{22}\)

B.

\(1.2 \times 10^{23}\)

C.

\(2.4 \times 10^{22}\)

D.

\(2.4 \times 10^{23}\)

Correct answer is A

\(1mole = 6.02 \times 10^{23} ions\)

\(0.02moldm^{-3} = 0.02 \times 6.02 \times 10^{23}\)

=\(0.1204 \times 10^{23} = 1.204 \times 10^{22}\)

\(\approxeq 1.2 \times 10^{22}\)

285.

Which of the following organic compounds can undergo both addition and substitution reactions?

A.

Pentane

B.

Benzene

C.

Propane

D.

Hexane

Correct answer is B

An example of benzene addition reaction is the formation of cyclohexane by a mix of benzene vapour and hydrogen passed over nickel catalyst; while chlorobenzene is formed by substitution reaction.