Waec Chemistry 2021 Past Questions and Answers

Question 6:

• WAEC 2021

The most common method of preparing insoluble salts is by ____________

A. Filtration
B. Decomposition
C. Neutralization
D. Double decomposition

Question 7:

• WAEC 2021

What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm\(^{2}\) cylinder?
[R = 0.082 atm dm\(^{3}\) mol\(^{-1}\) K\(^{-1}\)]

A. 0.32
B. 1.56
C. 3.13
D. 31.25

Question 8:

• WAEC 2021

The basic property of salts used as drying agents is by

A. Efforescence
B. High melting point
C. Hygroscopy
D. Low solubility

Question 9:

• WAEC 2021

What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper(II) ions?

A. Blue precipitate is formed which is soluble in excess ammonia
B. Brick red precipitate is produced which is insoluble in excess ammonia
C. Which precipitate is formed which is excess in ammonia
D. Green precipitate is formed which is insoluble in excess ammonia

Question 10:

• WAEC 2021

When CuSO\(_{4(aq)}\) is added to Pb(NO\(_{3}\))\(_{2(aq)}\)--------

A. There would be no visible change
B. A blue precipitate would be formed
C. The resulting solution would become colourless
D. A white precipitate would be formed