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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.

1,221.

The number of sulphur atoms in 3.20g of SO2(g) is [O = 16.0;S = 32.0; Avogadro constant = 6.02 x 1023]

A.

3.01 x 1022

B.

6.02 x 1022

C.

6.02 x1023

D.

1.20 x 1024

Correct answer is A

32g of sulphur = 64g / 6.02 x 1023 atoms of SO2

xg of sulphur = 3.2g of SO2 

: 1.6g of sulphur is present in 3.2g / 3.01 x 1023 atoms of SO2  

1,222.

Consider the following reaction equation: CaCO3(s) + 2HCI(aq) → CaCl2(aq) + H2O(l) + CO2(g). What mass of CaCI2 would be obtained when 25.0g of CaCO3(s) is reacted with excess HCI(aq)? [CaCO3=100;CaCI\(2 = 111]

A.

4.00g

B.

4.44 g

C.

18.9 g

D.

27.8 g

Correct answer is D

CaCO3 + 2HCI → CaCI2 + H2O + CO2

100g CaCO3 will produce 111g CaCI2

25g CaCO3 will produce x ,

x = 25x111100

= 27.75  27.8g

1,223.

MgO does not readily dissolve in water because

A.

of its high melting point

B.

it is a covalent compound

C.

it forms a hydroxide when dissolved in water

D.

its lattice energy is higher than its hydration energy

Correct answer is D

No explanation has been provided for this answer.

1,224.

The vapour pressure of a liquid depends on l. temperature. ll. rate of condensation. III. cohesive forces holding the particles together

A.

l only

B.

l and ll only

C.

l and lll only

D.

ll and lll only

Correct answer is C

Three common factors that influence the vapor pressure of a liquid are the surface area, intermolecular forces and the temperature.

1,225.

The complex compound formed when aluminum dissolves in aqueous sodium hydroxide is

A.

Na3Al(OH)4.

B.

NaAl(OH)4

C.

NaAl(OH)3

D.

Na2Al(OH)3

Correct answer is B

When aluminium is treated with dilute sodium hydroxide it forms a salt called sodium tetrahydroxoaluminate and hydrogen gas.