Waec Chemistry 2011 Past Questions and Answers

Question 46:

• WAEC 2011

Which of the following processes does not involve the use of limestone?

A. Extraction of iron in the blast furnance
B. Manufacture of tetraoxosulphate (VI) acid by Contact process
C. Production of washing soda by Solvay process
D. Production of cement

Question 47:

• WAEC 2011

Aluminium is extracted electrolysis from

A. Bauxite
B. Cryolite
C. Duralumin
D. Kaolin

Question 48:

• WAEC 2011

(a)The table below gives the volume/pressure data for a particular sample of a gas-at a given temperature.

Volumedm\(^3\) (V)	4.00	2.00	1.00
Pressure/atm (P)	1.00	2.00	4.00

(i) Deduce a mathematical relationship between volume (V) and pressure (P).
(ii) Name law that can be deduced from the data.
(iii) Calculate the pressure of the gas when the volume is 3.20 dm\(^3\)

(b)(i) What is the role of a salt bridge in an electrochemical cell?
(ii) What type of ions must flow into the cathode? Give a reason for your answer.
(iii)A standard galvanic cell constructed with Ag\(^+_{(aq)}\) Ag\(_{(s)}\) and Zn\(^{2+}_{(aq)}\) couple is discharged until 3.3 g of Ag forms.
I. Write the overall cell reaction and standard cell potential?
II. How many moles of electrons flowed through the circuit during the discharge?
III. How many coulombs of charges flowed through the circuit?
Ag\(^+_{(aq)}\) + e\(^-\) \(\rightleftharpoons\) Ag\(_{(s)}\); E° = + 0.80V
Zn\(^{2+}_{(aq)}\) + 2\(^-\) \(\rightleftharpoons\) Zn\(_{(s)}\), E° = – 0.76 V [Ag = 108]

(c)(i) Define each of the following terms: I. Activation energy; II. Exothermic reaction.
(ii) Give one example of an endothermic process.
(iii) What is the significance of activated complex in a chemical reaction?

Question 49:

• WAEC 2011

The following table gives the atomic numbers of elements V, W, X, Y and Z.

Element	V	W	X	Y	Z
Atomic number	11	16	18	19	24

(a)Which of the elements: (i) belong(s) to group 1?
(ii) is/are riotle gas(es)?
(iii) form(s) coloured compound(s)?
(iv) form(s) an anion?
(v) react(s) with water to liberate hydrogen?
(vi) react(s) with water to form alkaline solution?

(b) What is the:
(i) charge on the ion formed in
(a)(iv) above?
(ii) group of the element(s) in (a)(i) above?

(c)(i) Write the formula of the compound formed between element V and element W.
(ii) Sate the type of bond formed in (c)(i) above. Explain your answer.
(d)(i) What is a covalent compound?
(ii) Give two factors that influence covalent bonding.
(iii) State the type of bond that exists in each of the following substances: MgO, NH\(_3\) and Fe.
(iv) What are intermolecular forces?

Question 50:

• WAEC 2011

(a)Define the term solubility.
(b) The table below gives the solubility of salt Z at various mperatures

Temperature (°C)	0	10	20	30	40	50	60
Solubility (mol dm\(^{-3}\))	0.13	0.21	0.31	0.45	0.63	0.85	1.10

(i) Plot a graph of solubility against temperature.
(ii) From the graph determine the solubility of salt Z at 35°C.
(iii) If 100cm\(^{-3}\) of the saturated solution is cooled from 55°C to 35°C, calculate the mass of salt Z that would crystallize out. [Molar mass of salt Z = 100 g]

(c)(i) Write a balanced equation to illustrate the reaction of AI\(_2\)O\(_3\) with dilute I. HCI; II. NaOH.
(ii) What is the name given to an oxide that exhibits both acidic and basic properties?
(iii) Give one metallic oxide which exhibite these properties.

(d)(i) Determine the oxidation number of: I. Al in [Al (H\(_2\)O)\(_6\)]\(^{3+}\); II. H in NaH.
(ii) Give the IUPAC name of each of the following substances; I. CuSO\(_4\).5H\(_2\)O; II. CaCO\(_3\); Ill. KMnO\(_4\).