Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

3,401.

H2(g) + Br2(g) → 2HBr(g)
The above reaction is carried out at 25oC. ΔH is -72 kJ mol-1 and ΔS is - 106 J mol-1K-1, the reaction will?

A.

not proceed spontaneously at the given

B.

proceed spontaneously at the given temperature

C.

proceed in the reverse direction at the given temperature

D.

proceed spontenously at lower temperature

Correct answer is B

 Where ∆G = ∆H - T∆S

Given data; ∆G = ?

∆H = -72KJ/mol, 

T→ (25+273)K = 298K

∆S = -106J/mol or -0.106KJ/mol/K

: ∆G = -72 -(298 * -0.106)

= -72 + 31.588

∆G = -40.412KJ/mol

One of the condition for spontaneity of a reaction as ∆G to be negative.

3,402.

Trioxonitrate (V) acid is not used for preparing hydrogen gas from metals because it

A.

is strongly oxidizing

B.

is volatile

C.

renders the metal passive

D.

forms a layer of oxide on the metal

Correct answer is A

No explanation has been provided for this answer.

3,403.

The ion that can be used as an oxidizing agent is

A.

Au3+

B.

Fe3+

C.

ClO-

D.

Ca2+

Correct answer is C

No explanation has been provided for this answer.

3,405.

If 30cm3 of gas at 50oC is warmed to 80o at a fixed pressure, the fractional increase in volume is

A.

0.009

B.

0.093

C.

0.910

D.

1.090

Correct answer is D

No explanation has been provided for this answer.