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.

3,396.

Na2CO3(g) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
How many moles of sodium trioxocarbonate (IV) are there in a 25 cm3 solution which required 10cm3 of 0.05 mol dm-3 hydrochloric acid solution to neutralize it?

A.

1.000 mole

B.

0.100 mole

C.

0.010 mole

D.

0.111 mole

Correct answer is C

\(\frac{C_A V_A}{C_BV_B} = \frac{a}{b}\)

\(\frac{0.05 \times 10}{C_B \times 25} = \frac{2}{1}\)

50CB = 0.5

CB = \(\frac{0.5}{50} = \frac{1}{100}\)

= 0.01

3,397.

In the electrolysis of CuSO4(g) using platinum electrodes, the reaction at the anode is

A.

4H+ + 4e- → 2H2

B.

4OH- + 4e- → 2H2O + O2

C.

2OH - 2e- → 2OH

D.

2OH- + 2OH- → 2H2O + O2

Correct answer is B

4OH<sup>-</sup> + 4e<sup>-</sup> → 2H<sub>2</sub>O + O<sub>2</sub> is the reaction of sun at the anode in the electrolysis of CuSO4 (g) 

3,398.

In which of the following is the oxidation number of sulphur equal to -2?

A.

SO3

B.

S8

C.

H2S

D.

SO2

Correct answer is C

No explanation has been provided for this answer.

3,399.

The solution that will conduct the highest amount of electricity is?

A.

0.5 mol dm-3 of hydrochloric acid

B.

2.0 mol dm-3 of hydrochloric acid

C.

0.5 mol dm-3 ethanoic acid

D.

2.0 mol dm-3 ethanoic acid

Correct answer is B

Hence, for most aqueous solutions, the more ions, the higher the conductivity.

Strong electrolytes ionize completely e.g strong acid, strong bases and some salts

While weak electrolytes ionize only partially e.g CH3COOH is regarded as acetic acid. 
It is a weak electrolyte. Acetic acid is regarded as weak electrolyte because its dissociation constant is low. 

3,400.

Zinc and carbon rods are used as anode and cathode respectively in a

A.

Leclanche cell

B.

lead accumulator

C.

Daniel cell

D.

voltaic cell

Correct answer is A

In a Leclanche cell, the anode and the cathode are a zinc rod and a carbon rod respectively. The electrolyte is an ammonium chloride solution or paste (wet or dry cell).