Waec Chemistry Past Questions For Year 2004
Question 26
An orange drink concentrate is suspected to contain traces of poisonous green dye and a harmless dye having the same boiling point. Which of the following techniques is most suitable for isolating the dyes?
- A. Fractional distillation
- B. Paper chromatography
- C. Coagulation
- D. Recrystallization
Question 27
Which of the following factors that affect the rate of chemical reactions can be explained in terms of the collision theory? l. concentration ll. pressure lll. temperature lV catalyst
- A. l and ll only
- B. l, ll and lll only
- C. l and lll only
- D. l, II, lll and IV only
Question 28
WHICH OF THE FOLLOWING SALTS IS READILY SOLUBLE IN WATER?
- A. PbCI2
- B. Pb(NO 3) 2
- C. PbSO4
- D. PbCO 3
Question 29
What of the following pairs of acid and base will produce a solution with pH less than 7 at equivalence point?
- A. HNO3 and NaOH
- B. H2SO4 and KOH
- C. HCI and Mg(OH) 2
- D. HNO 3 and KOH
Question 30
What is the change in the oxidation number of 1- in the reaction represented by the following equation? 51 -1(aq) + 6H+(aq) + 1O-3(aq) → 312(g) + 3H2O(l)
- A. -5 to -3
- B. -1 to 0
- C. + 5 to + 0
- D. -1 to + 2
