WAEC Past Questions and Answers - Page 1612

8,056.

What will happen if more heat is applied to the following system at equilibrium? X2(g) + 3Y 2(g) ⇌ 2XY3(g); ∆H =-kJmol -1

A.

the yield of XY 3 will decompose

B.

more of XY3 will decompose

C.

More of X2 will react

D.

the forward reaction will go to completion

Correct answer is B

No explanation has been provided for this answer.

8,057.

Which of the following salt solutions will have a pH greater than 7?

A.

NaCl(aq)

B.

Na2CO3(aq)

C.

Na2SO4(aq)

D.

NaHSO4(aq)

Correct answer is B

No explanation has been provided for this answer.

8,058.

Calculate the mass of sodium hydroxide in 5.00 dm3 of a 0.125 mol dm-3 solution [NaOH = 40 g mol]

A.

0.0156 g

B.

0.625 g

C.

1.00 g

D.

25.0 g

Correct answer is D

1 mole of NaOH per dm3 has a mass of 40g mass of NaOH in 0.125 mole = 0.125 x 40 = 5g mass in 5.00 dm3 of the solution = 5 x 5 = 25.0g

8,059.

Which of the following substances increases in mass when heated in air?

A.

Sodium chloride

B.

lodine crystals

C.

magnesium ribbon

D.

copper (ll) oxide

Correct answer is C

No explanation has been provided for this answer.

8,060.

A substance is said to be hygroscopic if it absorbs?

A.

water from the atmosphere to form a solution

B.

heat from the surrounding

C.

carbon (IV) oxide from the atmosphere

D.

moisture from the atmosphere without dissolving

Correct answer is D

Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment,

which is usually at normal or room temperature.

Deliquescence, the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution.