Chemical combination - Jamb Chemistry Past Questions and Answers

Question 16:

• JAMB 1981

Na₂CO₃ + 2HCI → 2NaCI + H₂O + CO₂. Using the above equation, what volume of carbondioxide, measured at s.t.p is liberated when 53g of sodium carbonate is dissolved in hydrochloric acid?
(1 mole of gas occupies 22.4 dm³ at s.t.p)
(Na = 23, C = 12, O = 16)

A. 44.8 dm³
B. 11.2 dm³
C. 100.1 dm³
D. 3.0 dm³
E. 22.4 dm³

Question 17:

• JAMB 1981

If 48,000 coulombs of electricity are required to discharge 0.5 mole of sodium from a molten sodium chloride mass, then the number of coulombs required to discharge 2 moles of lead from molten lead (ll) chloride is?

A. 48,000
B. 96,000
C. 192,000
D. 384,000
E. 576,000

Question 18:

• JAMB 1981

If one mole of aluminium contains 6 x 10²³ atoms of aluminium, how many atoms are contained in 0.9g of aluminium?
(Al = 27)

A. 1.0 x 10²¹
B. 6.6 x 10²¹
C. 2.0 x 10²²
D. 1.0 x 10²²
E. 5.4 x 10²³

Question 19:

• JAMB 1982

1.00 g of the oxide of metal X (atomic mass = 64) gave 0.80 g of the metal when reduced with hydrogen.
The formula of the oxide is?

A. X₂O
B. XO
C. XO₂
D. X₂O₃
E. X₃O₄

Question 20:

• JAMB 1982

A mixture contains 20cm³ of hydrogen, 35cm³ of oxygen, 15cm³ of carbon monoxide and 10cm³ of nitrogen at S.T.P. Which of the following gives the mole fraction of hydrogen in this mixture?

A. 0.02
B. 0.16
C. 0.20
D. 0.25
E. 20