WAEC Past Questions and Answers - Page 1346

6,726.

The properties of a good primary standard solution include the following except?

A.

High molecular mass

B.

low molecular mass

C.

high degree of purity

D.

readily available

Correct answer is B

Properties of a good standard solution

  • High purity.
  • Stability (low reactivity)
  • Low hygroscopicity (to minimize weight changes due to humidity)
  • High equivalent weight (to minimize weighing errors)
  • Non-toxicity.
  • Ready and cheap availability.
  •  High molecular mass

6,727.

The name of the compound CH\(_3\)C(CH\(_3\))\(_2\)CH\(_2\)CH\(_2\)CH\(_3\)

A.

2 - methyl butane

B.

2,2 - dimethyl butane

C.

2 - methyl pentane

D.

2,2 - dimethyl pentane

Correct answer is D

- The longest chain has five carbon atoms i.e PENT

- with two methyl attached to the second carbon atom 

6,728.

Which of the following compounds has coordinate bonds in its structure?

A.

Al\(_2\)Cl\(_6\)

B.

MgCl\(_2\)

C.

AgCl

D.

NaCl

Correct answer is A

Aluminum chloride (Al2Cl6) has coordinate dative bonding

6,729.

What is the percentage by mass of H in  CH3COOH

A.

1.7%

B.

5.0%

C.

6.7%

D.

7.1%

Correct answer is C

- molecular mass (or molar mass) is 60.05 g/mol

- with 4 atoms of hydrogen present

( 4 / 60 ) X 100

≈6.7%

6,730.

Stoichiometry is based on the law?

A.

multiple proportion

B.

constant composition

C.

conservation of energy

D.

conservation of mass

Correct answer is D

The principles of stoichiometry are based upon the law of conservation of mass. Matter can neither be created nor destroyed, so the mass of every element present in the product(s) of a chemical reaction must be equal to the mass of each and every element present in the reactant(s).