JAMB Chemistry Past Questions & Answers - Page 187

931.

If chlorine gas is bubbled into water and then this yellowish-green coloured solution is exposed to bright sunlight for a while

A.

the solution will give out chlorine gas and hydrogen chloried gas

B.

the solution will produce chlorine gas and oxygen

C.

the solution will give out solution will producing hypochloric acid

D.

the solution is decomposed giving out oxygen, hydrogen and chlorine

E.

the solution will give out oxygen gas leaving behind aqueous hydrochloric acid

Correct answer is E

No explanation has been provided for this answer.

932.

When ammonium, potassium and calcium carbonates are each separately heated

A.

none of them will decompose

B.

each of them will decompose to give carbondioxide and the respective oxide

C.

ammonium carbonate and potassium carbonate will not decompose

D.

only ammonium carbonate and the respective oxide

E.

ammonium carbonate will decompose to give carbondioxide, water and ammonia

Correct answer is E

Solid ammonium carbonate decomposes as it is heated.

 (NH4)2CO3 → 2 NH3 + CO2 + H2O

933.

How many grams of HBr would exactly be required to react with 2 g of propyne? (C =12, H=1, Br = 80)

A.

4.1g

B.

6.1g

C.

8.1g

D.

16.2g

Correct answer is C

2HBr + C3H4 \(\to\) C3H6 + 2Br

162gms of HBr reacts with 40gms of propyne 2gms of propyne will react with

\(\frac{162}{40} \times \frac{2}{1}\) = 8.1gms HBr

934.

\(50cm^{3}\) of hydrogen are sparked with \(20cm^{3}\) of oxygen at \(100°C\) and \(1atm\) . The total volume of the residual gases in

A.

50 cm3

B.

10 cm3

C.

40 cm3

D.

30 cm3

E.

70 cm3

Correct answer is A

The equation of the reaction is:

\(2H_{{2}{(g)}} + O_{{2}{(g)}} = 2H_{2}O_{(g)}\)

Before Sparking we have : \(50cm^{3} : 20cm^{3}\)

On Sparking, \(40cm^{3} : 20cm^{3} : 40cm^{3}\)

After Sparking, we have \(10cm^{3} : 0  : 40cm^{3}\)

Hence, the volume of residual gases = \((10+40)cm^{3} = 50cm^{3}\)

935.

Helium atoms are chemically unreactive because

A.

there are no electrons around the nucleus

B.

the number of protons equals the number of electrons

C.

there are equal number of protons and neutrons in the nucleus

D.

the outer electron shell is completely filled

E.

the atoms contain only protons

Correct answer is D

No explanation has been provided for this answer.