WASSCE 2019 Chemistry

The periodic table is an arrangement of elements according to their?

• Oxidation number

• Atomic number

• Mass number

• Number of neutrons

Answer explanation

Explanation

Elements are arranged in order of increasing atomic number

A solid with higher melting and boiling points is likely to be?

• A Covalent compound

• A Dative compound

• An Electrovalent compound

• A Non-metal

Answer explanation

Ionic Compounds / Electrovalent compounds Have A High Melting Point and High Boiling Point.

Calcium and magnesium belong to the group of the periodic table because both?

• are metals

• form cations

• form colourless salts

• have same number of valence electrons

Which of the substances is non-polar?

• Bromine

• Ammonia

• Water

• Hydrogen Bromide

Answer explanation

Br2 (Bromine) is nonpolar because, in this molecule, both bromine atoms have the same electronegativity due to which both atoms have equal charge distribution and results in a net-zero dipole moment.

Which of the following pairs of components have the same molecular mass?

[ H = 1.0, C = 12.0, O = 16.0 ]

Note: Ethene = C2H4

Ethyne = C2H2

• Ethene and Ethyne

• Ethane and Ethene

• Carbon (ii) Oxide and Ethene

• Carbon (iv) Oxide and Ethyne

Answer explanation

Ethene = 28

Ethyne = 26

Carbon(ii)Oxide = 28

Carbon(iv)Oxide = 44

How many moles of carbon(iv)oxide contains 16.0g of oxygen?

[ C = 12.0, O = 16.0 ]

• 0.20 mol

• 0.25 mol

• 0.40 mol

• 0.50 mol

Stoichiometry is based on the law?

• multiple proportion

• constant composition

• conservation of energy

• conservation of mass

What is the percentage by mass of H in  CH3COOH

• 1.7%

• 5.0%

• 6.7%

• 7.1%

Vinegar is an aqueous solution of?

• Hydrochloric acid

• hydrofluoric acid

• ethanedioc acid

• ethanoic acid

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

• Al2Cl6

• MgCl2

• AgCl

• NaCl