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.

21.

The oxidation state of carbon in HCOOH is

A.

-1

B.

+2

C.

+3

D.

zero

Correct answer is B

HCOOH
O.N of H + O.N of C + 2* O.N of oxygen of
H = 0
1 + X + 2X - 2 + 1 = 0
2 + X -4 = 0
X = 4 - 2 = +2

22.

Insoluble salts can be prepared by?

A.

titrating an alkali against an appropriate acid

B.

reacting an acid with trioxocarbonate (IV) salt

C.

directing combination of the elements which make up the salt

D.

mixing two soluble compounds containing the metallic radical and the acidic radic

Correct answer is D

An insoluble salt can be prepared by a precipitation method through a double decomposition reaction.

Two soluble metal salts react with each other to form one soluble salt and one insoluble salt .

Lead nitrate solution and sodium chloride solution react to produce solid lead chloride , leaving soluble sodium nitrate in solution.

The lead chloride can be recovered by filtration.

23.

0.05 mol dm-3 HCl is neutralized by 25 cm3 NaOH. If the volume of acid used is 32.00cm3, what is the concentration of the base

A.

0.016 mol dm-3

B.

0.032 mol dm-3

C.

0.039 mol dm-3

D.

0.064 mol dm-3

Correct answer is D

HCl + NaOH → NaCl + H2O
CAVA = NA/NB = (0.05 * 32)/(CB * 25)
∴ CB = (0.05 * 32)/25 = 0.064 mol dm-3

24.

The basicity of CH3COOH is

A.

1

B.

2

C.

3

D.

4

Correct answer is A

The basicity of CH3COOH is 1. Which means it has just one ionizable ion.

25.

What is the pH of 0.001 mol dm-3 solution of sodium hydroxide

A.

14

B.

13

C.

12

D.

11

Correct answer is D

\([H^+] [OH^-] = 10^{-14}\)
\([H^+] = 10^{-14}/[OH^-] = 10^{-14}/(1 * 10^{-3}) = 10^{-11}\)
pH = -Log10[H+]
= - Log10[10-11] = - 1 * -11 Log10[10-11] = 1 = -1 * -11 * 1 = 11

26.

The uncovered raw food that is sold along major roads is likely to contain some amounts of

A.

Pb

B.

Cu

C.

Ag

D.

Na

Correct answer is A

The uncovered raw food that is sold along major roads is likely to contain some amounts of lead(Pb).

27.

117.0g of sodium chloride was dissolved in 1.0dm3 of distilled water at 25°C. Determine the solubility in mol dm-3 of sodium chloride at that temperature
[Na = 23, Cl = 35.5]

A.

1.0

B.

2.0

C.

3.0

D.

4.0

Correct answer is B

Relative molecular mass of NaCl = 23 + 35.5 = 58.5 g/mol
No. of mole of NaCl = 117/58.5 = 2.0 mol

28.

The vulcanizer's solution is prepared by dissolving rubber in

A.

ethanol

B.

kerosine

C.

benzene

D.

petrol

Correct answer is C

Dissolved rubber in benzene makes the vulcanizer's solution.

29.

When a few drops of water is added to a blue anhydrous cobalt (II) chloride, the colour changes to

A.

white

B.

pink

C.

red

D.

blue

Correct answer is B

Blue anhydrous cobalt (II) chloride changes to pink in water

30.

In the course of purifying water for town supply the water is passed through large settlings tanks, containing sodium aluminate (III) to remove?

A.

large particles

B.

germs

C.

fine particles

D.

odour

Correct answer is C

Potash alum [kAl(S\({O}_4\))\(_2\)] n sodium aluminate (ii) (NaHCO\(_2\)) are added to cause coagulation.

As  fine particles to clump together, forming large particles heavy enough to settle at the bottom of the tanks as impurities.