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.

3,761.

56.00cm3 of a gas at S.T.P. weighed 0.11g. What is the vapour density of the gas?
[Molar volume of a gas at S.T.P = 22.4dm3]

A.

11.00

B.

22.00

C.

33.00

D.

44.00

Correct answer is B

56.00cm3 of a gas at S.T.P weighed 0.11g
Molar volume of the gas = 22.4dm3 = 22400cm3
molar mass = (22400 x 0.11)/56
molar mass = 2464/56 = 44
Vapour density = Molar mass/2 = 44/2 = 22

3,762.

200cm3 each of 0.1M solutions of lead (II) trioxonitrate(V) and hydrochloric acid were mixed. Assuming that lead (II) chloride is completely insoluble, calculate the mass of lead (II) chloride that will be precipitated.
[Pb = 207, Cl= 35.5, N = 14, O = 16]

A.

2.78g

B.

5.56g

C.

8.34g

D.

11.12g

Correct answer is A

HCl + Pb(NO3)2 ===> 2HNO3 + PbCl2
2moles of HCl ===> 1mole of PbCl2

n = CV/1000 = (100 x 0.2)/(1000) = 0.02 mol
n (HCl) = 0.02 mol

2 moles of HCl ===> 1 mole of PbCl2
0.02 mole of HCl ===> x mole of PbCl2
2x = 0.02
x = 0.01 mol

n = m/M
m = 0.01 x (207 + (35.5 x 2)) = 0.01 x 278 = 2.78 g       note; HCl is used for the calculation instead of lead(II) nitrate because it is the limiting reactant meaning it will be used up first before lead(11) nitrate

3,763.

Which of the following substances would you see as an indicator in the titration of sodium carbonate solution against hydrochloric acid (complete neutralisation)?

A.

Litmus paper

B.

Phenolphthalein

C.

Methyl orange

D.

Universal indicator

E.

None of these

Correct answer is C

No explanation has been provided for this answer.

3,764.

You are provided with five gas jars containing SO2, CO2, H2, CO and NO respectively. Select a test from A to E which will identify ANY ONE of the gases completely

A.

pass each gas into lime water

B.

pass each gas into water and test with litmus paper

C.

pass each gas into concentrated sulphuric acid

D.

expose each gas to atmospheric air

E.

expose each gas to fumes of hydrogen chloride

Correct answer is A

No explanation has been provided for this answer.

3,765.

A gas jar was inverted over burning yellow phosphorus floating over water in a beaker. After burning, the water level was found to rise in the gas jar. The water level rises because

A.

pressure inside the gas jar is greater than pressure outside it

B.

the air in the gas jar had been used up by burning

C.

oxygen in the gas jar had been used up by burning

D.

nitrogen in the gas jar had been used up by burning

E.

the temperature in the jar had risen considerably

Correct answer is C

No explanation has been provided for this answer.