Year :
2019
Title :
Chemistry
Exam :
WASSCE/WAEC MAY/JUNE
Paper 1 | Objectives
21 - 30 of 50 Questions
| # | Question | Ans |
|---|---|---|
| 21. |
The most suitable indicator for the reaction between NaOH and HCOOH is? A. bromocresol B. methyl orange C. methyl red D. phenolphthalein Detailed SolutionPhenolphthalein is suitable as indicator for this reaction i.e strong base and weak acid |
|
| 22. |
Consider the following reaction equation: 2Al(OH)\(_3\) + 3H\(_2\)SO\(_4\) →Al\(_2\)(SO4)\(_3\)(aq)+6H\(_2\)O. How many moles of tetraoxosulphate(vi)acid is needed to produce 0.5mol of aluminium tetraoxosulphate(vi)? A. 0.5 B. 1.0 C. 1.5 D. 3.0 |
|
| 23. |
Which of the following pairs of substances has the highest heat of neutralization? A. strong acid and strong base B. weak acid and weak base C. strong acid and weak base D. weak acid and strong base Detailed SolutionIn other terms, the stronger the acid the greater the amount of hydrogen ions present in the solution, and hence the more alkali that should be required to neutralise the solution, hence increasing the enthalpy |
|
| 24. |
When quicklime dissolves in water? A. heat is absorbed B. heat is evolved C. oxygen is liberated D. hydrogen is given off Detailed Solution- When quicklime is added to water, it forms slaked lime along with the evolution of heat. There will be a rise in the temperature of the bucket. Calcium oxide reacts with water to form calcium hydroxide, also called slaked lime.- That is adding water to quicklime produces an exothermic reaction (gives out heat) and hydrated lime. |
|
| 25. |
If the value of ΔH is positive for a reaction, it means that the reaction is? A. exothermic B. endothermic C. spontaneous D. slow Detailed Solution- Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.- A system of reactants that absorbs heat from the surroundings in an endothermic reaction has a positive ΔH. - examples of endothermic processes: |
|
| 26. |
Which of the following compounds is formed by the oxidation of ethanol? A. C\(_2\)H\(_4\)CO\(_2\)H B. C\(_2\)H\(_5\)CO\(_2\)H C. CH\(_3\)OH D. CH\(_3\)CO\(_2\)H Detailed Solution-Potassium dichromate solution is acidified with dilute sulphuric acid to oxidise ethanol into ethanoic acid. |
|
| 27. |
What is the name of the gas liberated when diluted hydrochloric acid is added to iron(ii)sulphide? A. turns lime water milky B. decolorizes bromine water C. gives a pop sound D. turns lead(ii)ethanoate paper black Detailed Solution- Iron sulfide reacts with hydrochloric acid, releasing hydrogen sulfide: FeS + 2HCl → FeCl\(_2\) + H\(_2\)S.- Hydrogen sulfide reacts with lead acetate to form lead sulfide and thus produces a coloration on the paper which will vary from yellow to black, depending upon the amount of hydrogen sulfide present. |
|
| 28. |
An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound?[ H = 1.0. C = 12.0, O = 16.0 ] A. C\(_3\)H\(_8\)O B. C\(_6\)H\(_12\)O C. C\(_6\)H\(_12\)O\(_2\) D. C\(_12\)H\(_12\)O\(_11\) Detailed SolutionC = 72 / 12 H = 12 / 1 O = 16 / 16C = 6 H = 12 O = 1 : EMPIRICAL FORMULA C\(_6\)H\(_12\)O |
|
| 29. |
When excess chlorine is mixed with ethane at room temperature, the product formed is? A. 1,2-dichloroethane B. 1,2-dichloroethene C. 1,1-dichloroethane D. 1,1-dichloroethene Detailed Solution- The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon |
|
| 30. |
Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol A. H+ / K2Cr2O7 B. I\(_2\) / OH- C. CH\(_3\)COOH D. NaCl Detailed Solutionwhen a primary alcohol like ethanol is warmed with excess of an oxidizing reagent, such as acidified Potassium permanganate( KMnO₄) or acidified Potassium dichromate(VI) ( K2Cr2O7 ), it is oxidized first to ethanal then to ethanoic acid, WHILESecondary alcohols like butan-2-ol will be oxidized to alkanones propan-1-ol - primary alcohol, propan-2-ol- secondary alcohol - The Lucas test in alcohols is a test to differentiate between primary, secondary, and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides |
| 21. |
The most suitable indicator for the reaction between NaOH and HCOOH is? A. bromocresol B. methyl orange C. methyl red D. phenolphthalein Detailed SolutionPhenolphthalein is suitable as indicator for this reaction i.e strong base and weak acid |
|
| 22. |
Consider the following reaction equation: 2Al(OH)\(_3\) + 3H\(_2\)SO\(_4\) →Al\(_2\)(SO4)\(_3\)(aq)+6H\(_2\)O. How many moles of tetraoxosulphate(vi)acid is needed to produce 0.5mol of aluminium tetraoxosulphate(vi)? A. 0.5 B. 1.0 C. 1.5 D. 3.0 |
|
| 23. |
Which of the following pairs of substances has the highest heat of neutralization? A. strong acid and strong base B. weak acid and weak base C. strong acid and weak base D. weak acid and strong base Detailed SolutionIn other terms, the stronger the acid the greater the amount of hydrogen ions present in the solution, and hence the more alkali that should be required to neutralise the solution, hence increasing the enthalpy |
|
| 24. |
When quicklime dissolves in water? A. heat is absorbed B. heat is evolved C. oxygen is liberated D. hydrogen is given off Detailed Solution- When quicklime is added to water, it forms slaked lime along with the evolution of heat. There will be a rise in the temperature of the bucket. Calcium oxide reacts with water to form calcium hydroxide, also called slaked lime.- That is adding water to quicklime produces an exothermic reaction (gives out heat) and hydrated lime. |
|
| 25. |
If the value of ΔH is positive for a reaction, it means that the reaction is? A. exothermic B. endothermic C. spontaneous D. slow Detailed Solution- Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.- A system of reactants that absorbs heat from the surroundings in an endothermic reaction has a positive ΔH. - examples of endothermic processes: |
| 26. |
Which of the following compounds is formed by the oxidation of ethanol? A. C\(_2\)H\(_4\)CO\(_2\)H B. C\(_2\)H\(_5\)CO\(_2\)H C. CH\(_3\)OH D. CH\(_3\)CO\(_2\)H Detailed Solution-Potassium dichromate solution is acidified with dilute sulphuric acid to oxidise ethanol into ethanoic acid. |
|
| 27. |
What is the name of the gas liberated when diluted hydrochloric acid is added to iron(ii)sulphide? A. turns lime water milky B. decolorizes bromine water C. gives a pop sound D. turns lead(ii)ethanoate paper black Detailed Solution- Iron sulfide reacts with hydrochloric acid, releasing hydrogen sulfide: FeS + 2HCl → FeCl\(_2\) + H\(_2\)S.- Hydrogen sulfide reacts with lead acetate to form lead sulfide and thus produces a coloration on the paper which will vary from yellow to black, depending upon the amount of hydrogen sulfide present. |
|
| 28. |
An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound?[ H = 1.0. C = 12.0, O = 16.0 ] A. C\(_3\)H\(_8\)O B. C\(_6\)H\(_12\)O C. C\(_6\)H\(_12\)O\(_2\) D. C\(_12\)H\(_12\)O\(_11\) Detailed SolutionC = 72 / 12 H = 12 / 1 O = 16 / 16C = 6 H = 12 O = 1 : EMPIRICAL FORMULA C\(_6\)H\(_12\)O |
|
| 29. |
When excess chlorine is mixed with ethane at room temperature, the product formed is? A. 1,2-dichloroethane B. 1,2-dichloroethene C. 1,1-dichloroethane D. 1,1-dichloroethene Detailed Solution- The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon |
|
| 30. |
Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol A. H+ / K2Cr2O7 B. I\(_2\) / OH- C. CH\(_3\)COOH D. NaCl Detailed Solutionwhen a primary alcohol like ethanol is warmed with excess of an oxidizing reagent, such as acidified Potassium permanganate( KMnO₄) or acidified Potassium dichromate(VI) ( K2Cr2O7 ), it is oxidized first to ethanal then to ethanoic acid, WHILESecondary alcohols like butan-2-ol will be oxidized to alkanones propan-1-ol - primary alcohol, propan-2-ol- secondary alcohol - The Lucas test in alcohols is a test to differentiate between primary, secondary, and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides |