Question

An air sample consists of oxygen and nitrogen gas as major components. It also contains carbon dioxide and traces of some rare gases. All these gases are evenly distributed throughout the sample of air. Which term or terms could be used to describe this sample of air? Check all that apply.

Answer 1

• a) mixture

• c) homogeneous mixture

• d) solution

Step-by-step explanation:

The relevant definitions that you must know to answer this question are:

Pure substance: matter that has a unique fixed (invariable) uniform composition. Only elements and compounds are pure substances.

Element: matter formed by one single kind of atoms. For instance, hydrogen, oxygen, sodium. There are 118 known elements and they are all listed in the periodic table.

Compound: pure substances formed by two or more kind of atoms. For instance: H₂O, CO₂, NaOH, CH₃OH. Every compound has its own chemical compositon. There are infinetely many different compounds.

Mixture: a mixture is a combination of two or more pure substances, in any proportion. Each pure substance retains its own properties in the mixture.

Homogeneous mixture: a mixture in which the components cannot be distinguished by physical media. Alll the components are in the same phase and the compositon of the mixture is uniform.

Solutions: homogeneous mixtures.

Heterogeneous mixture: mixtures in which the individual components can be distinguished by physical media. E.g. the mixture of sand and water.

With that you can go through each choice:

a) mixture: Correct. Indeed air is a mixture because it is formed by several compounds (carbon dioxide, CO₂) and other gases.

b) heterogeneous mixture: Wrong. It is not heterogeneous because its components are evenly distributed throughout the sample of air and they cannot be distinguished one from each other by physical media.

c) homogeneous mixture: Correct. This is a homogeneous mixture, for the same reason explained in b)

d) solution: Correct. Solutions are homogeneous mixtures.

e) pure chemical substance: Wrong. Pure chemical substances are composed either by one kind of atoms or one kind of compound. Since there are several different elements and compouds this is not a pure chemical substance.

f) compound: Wrong. Carbon dioxide (CO₂) is a compound, but there are other compounds and elements present in the sample of air.

g) element: Wrong. Oxygen is an element (it has only oxygen atoms), but there are other elements and compounds.