WAEC Past Questions and Answers - Page 1528

7,636.

Which of the following statements about rare gases are correct?

A.

Their outermost shells are fully filled

B.

They are generally unreactive

C.

Their outermost shells are partially filled

D.

They have lone pair of

Correct answer is A

No explanation has been provided for this answer.

7,637.

When sodium atom form the ion Na+,

A.

it gains one proton

B.

it achieves a noble gas configuration

C.

its atomic number increases

D.

it gains one electron

Correct answer is B

When the sodium atom forms an ion, Na+ it loses one electron, i.e. it achieves a noble gas electronic configuration. It will lose one of its 11 electrons to have 10 electrons like neon.
\(Na - e^- → Na^+\)
Na → \(Na^+ + e^-\)

7,638.

One advantage of cross breeding is that the

A.

Offspring resemble the recessive parent

B.

Yield of the offspring may not be comparable to those of the parents

C.

Offspring performs better than the average of the parents

D.

Offspring cannot survive adverse environmental conditions

Correct answer is C

No explanation has been provided for this answer.

7,639.

Which of the following equations represents a substitution reaction?

A.

C 2H10(g) + CI 2(g) → C4H9 CI(g) + HCI(g)

B.

C 2H4(g) + HCI (g) → C 2H5 CI(l)

C.

C2H2(g) + 2H 2(g) → C 2H6(g)

D.

C 3H4(g) + 402(g) → 3CO2(g) + 2H 2O(g)

Correct answer is A

No explanation has been provided for this answer.

7,640.

The ammonium compound used in the manufacture of dry cells is

A.

NH4NO3

B.

(NH4)SO4

C.

NHCI4

D.

(NH4)2CO3

Correct answer is C

No explanation has been provided for this answer.