WAEC Past Questions and Answers - Page 1343

6,711.

If a catalyst is added to a system, the temperature and the pressure remain constant, there would be no effect on the? 

A.

activation energy of the reaction

B.

rate of the reaction

C.

rate of the reverse reaction

D.

heat of reaction

Correct answer is D

No explanation has been provided for this answer.

6,712.

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

Correct answer is A

when 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, WHILE

Secondary 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 

6,713.

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

Correct answer is A

- The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon

6,714.

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\(_11\)

Correct answer is B

C = 72 / 12       H = 12 / 1       O = 16 / 16

C = 6               H = 12             O = 1

: EMPIRICAL FORMULA

C\(_6\)H\(_12\)O

6,715.

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

Correct answer is D

- 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.