WAEC Chemistry Past Questions & Answers - Page 277

1,381.

Which of the processes represented by the following equations has the greatest positive entropy change?

A.

C6H3(l) → C6H 6 (g)

B.

H2O (s) → H2O(l)

C.

CuO(s) + H2(g) → Cu(s) + H2

D.

Na2CO3(s) + nH2O(l) →Na 2CO3nH2O(s)

E.

S(s) → S(l)

Correct answer is A

we have the greatest entropy when a substance changes from the liquid phase to the gaseous phase this is because the particles of gases are very loosely packed so they have the freedom to move around.

1,382.

What is the amount (in mole) of sodium trioxocarbonate (IV) in 5.3 g of the compound? (Na2CO3 = 106)

A.

0.05

B.

0.10

C.

0.20

D.

0.50

E.

2.00

Correct answer is A

No explanation has been provided for this answer.

1,383.

When air is passed through a heated tube containing finely divided copper, the component that is absorbed in the process is

A.

carbon (IV) oxide

B.

nitrogen

C.

oxygen

D.

water vapour

E.

noble gases

Correct answer is C

No explanation has been provided for this answer.

1,384.

The separation of a mixture of calcium trioxocarbonate (lV) and sodium trioxocarbonate (IV) is most easily carried out by using the differences in their

A.

physical states

B.

melting points

C.

Rf. values

D.

solubility

E.

boiling points

Correct answer is D

No explanation has been provided for this answer.

1,385.

In which of the following is the oxidation number of nitrogen zero?

A.

SO2 and NH3

B.

NaNO3

C.

HNO2

D.

NOI3

E.

N2

Correct answer is E

No explanation has been provided for this answer.