IGCSE Chemistry Unit 4

The name of P₄S₁₀ is

• phosphorous sulfide

• phosphorus sulfide

• tetraphosphorus decasulfide

• phosphorus (X) sulfide

Answer explanation

The formula P₄S₁₀ indicates 4 phosphorus (P) atoms and 10 sulfur (S) atoms. The correct IUPAC name is tetraphosphorus decasulfide, reflecting the number of each element in the compound.

A covalent compound made of one sulfur and two oxygen atoms would be named

• sulfur dioxide.

• sulfur oxide.

• disulfur oxide.

• sulfide oxygen.

Answer explanation

The compound consists of one sulfur and two oxygen atoms. According to naming conventions, it is called sulfur dioxide, where 'di-' indicates two oxygen atoms. The other options do not correctly represent this compound.

The chemical formula of sulfur hexabromide is

• SBr₆

• S₆Br

• S(VI)Br

• S6Br

Answer explanation

The correct chemical formula for sulfur hexabromide is SBr₆, indicating one sulfur atom bonded to six bromine atoms. The other options do not accurately represent the composition of the compound.

The covalent compound N₂O₅ would be named

• nitrogen oxide.

• dinitrogen oxide.

• nitrogen pentoxide.

• dinitrogen pentoxide.

Answer explanation

The compound N2O5 contains two nitrogen atoms and five oxygen atoms. The prefix 'di-' indicates two, and 'penta-' indicates five, leading to the correct name: dinitrogen pentoxide.

The name of SO₃ compound is

• sulfate

• sulfur oxide

• sulfur trioxide

• monosulfur trioxide

Answer explanation

The compound SO₃ is named sulfur trioxide, indicating it contains one sulfur atom and three oxygen atoms. The other options do not accurately represent this chemical formula.

silicon dioxide

• SO₂

• NaO₂

• SiO₂

• SiO

Answer explanation

Silicon dioxide is chemically represented as SiO₂. The other options, SO₂ (sulfur dioxide) and NaO₂ (sodium oxide), are different compounds, while SiO is silicon monoxide, not dioxide.

carbon monoxide

• CO

• CO₂

• C₂O

• COH

Answer explanation

Carbon monoxide is represented by the chemical formula CO, which consists of one carbon atom and one oxygen atom. The other options, CO₂, C₂O, and COH, represent different compounds.

NO

• Nitrogen oxide

• Mononitrogen monoxide

• Nitrogen monoxide

• Nitrogen monoxygen

Answer explanation

The correct answer is 'Nitrogen monoxide' because it accurately describes the chemical compound with one nitrogen and one oxygen atom, commonly known as NO. The other options are incorrect or not standard nomenclature.

In the formula for calcium chloride, CaCl₂, there are ___ atoms of chlorine in a formula unit.

• 1

• 2

• 3

• it is estimated in the billions, but we're not sure

Answer explanation

In the formula for calcium chloride, CaCl2, the subscript '2' indicates there are 2 atoms of chlorine in each formula unit. Therefore, the correct answer is 2.

The compound calcium chloride, CaCl₂,uses _______ bonds to hold the atoms together.

• metallic

• ionic

• covalent

• intrinsic

Answer explanation

Calcium chloride, CaCl2, is formed through ionic bonds, which occur between the positively charged calcium ions (Ca²⁺) and negatively charged chloride ions (Cl⁻). This type of bond is characteristic of compounds formed from metals and nonmetals.