Waec Chemistry 2019 Past Questions and Answers

Question 51:

• WAEC 2019

Which of the following methods is NOT used for the separation of mixtures?

A. Chromatography
B. Crystallization
C. Distillation
D. Electrolysis

Question 52:

• WAEC 2019

The group to which elements belong in the periodic table is determined by the number?

A. Electrons
B. Core electrons
C. Valence shells
D. Valence electrons

Question 53:

• WAEC 2019

Kipps apparatus can be used to prepare?

A. H\(_2\)
B. NH\(_3\)
C. O\(_2\)
D. H\(_2\)S

Question 54:

• WAEC 2019

(a) Explain briefly why \(_2^4He\) has a stable electron configuration compared to \(_4^9Be\)
(b) Consider the following elements: 1H and 3Li.
(i) State the number of electrons that an atom of each element would have after forming an ionic bond.
(ii) Give a reason for each of your answers stated in (b)(i).
(c) State two factors that should be considered when siting a chemical industry.

(d) State two advantages of using a catalyst instead of high temperatures in chemical reactions.
(e) Turpentine burns in chlorine according to the following equation:
C\(_{10}\)H\(_{16}\)\(_{(I)}\) + 8Cl\(_{2(g)}\) \(\to\) 10C\(_{(s)}\) + 16HCl\(_{(g)}\)
Calculate the mass of turpentine that would completely burn in 21.3 g of chlorine.
[Molar mass of chlorine = 71 gmol\(^{-1}\); Molar mass of Turpentine = 136 gmol\(^{-1}\)]

(f) What is cracking?

(g) State two factors that may influence the value of electron affinity.

(h) What are carbohydrates?

(i) State two differences between a simple sugar and starch.

(j) Write an equation to show the dissociation of each of the following acids:
(i) H\(_2\)CO\(_3\);
(ii) CH\(_3\)COOH.

Question 55:

• WAEC 2019

(a) (i) Name three different methods for preparing salts.
(ii) Give one example of a balanced equation for each of the methods named in (a)(i).
(iii) State two uses of sodium trioxocarbonate (IV).
(b) If you were given some impure copper, describe how you would
obtain a specimen of the pure metal by electrolysis.

(c) Given that sodium chloride has a solubility of 36.3 at 30 and 39.0 at
100 and that of silver nitrate is 297.0 at 30 and 952.0 at 100.

(i) Calculate the percentage of each substance in the saturated solution at 100 that is deposited on cooling to 30

(ii) Deduce which of the two salts can be purified more efficiently by crystallization.