Foundations of Chemistry Practice Quiz (27 questions)

1. Which set of subjects falls within the scope of chemistry?

A. The measurement of distances, shapes, and relationships between geometric figures

B. The classification of organisms, their environments, and patterns of inheritance

C. The composition, properties, and structure of substances, along with their changes and reaction mechanisms

D. The motion of objects, forces acting on them, and changes in their positions

Answer: (C)

Explanation

Chemistry examines substances’ composition, properties, and internal structure, as well as how they change and how reactions occur. The study of motion and forces is more closely associated with mechanics in physics.

2. A material changes from a solid to a liquid while keeping the same chemical composition; how should this change be classified?

A. As a physical change, because its state changes while its composition remains the same

B. As a chemical change, because any change in state produces a new substance

C. As a chemical change, because energy is involved in the transformation

D. As a physical change, because the material’s composition becomes different

Answer: (A)

Explanation

A physical change can alter a substance’s energy or aggregate state without changing its composition. A change of state does not, by itself, mean that a new substance has formed.

3. Which statement correctly describes mass and its standard unit of measurement?

A. Mass is the energy stored in matter measured in joules

B. Mass is the gravitational force on matter measured in newtons

C. Mass is the volume occupied by matter measured in cubic metres

D. Mass is a basic property of matter measured in kilograms

Answer: (D)

Explanation

Mass is a basic property of matter, and its unit is the kilogram. Gravitational force is weight, not mass, and is expressed in newtons.

4. An object has mass $m$ in a gravitational field with acceleration $g$; which expression gives its weight force?

A. $F=mg$

B. $F=g-m$

C. $F=\frac{m}{g}$

D. $F=m+g$

Answer: (A)

Explanation

Weight force is calculated by multiplying an object’s mass by gravitational acceleration, giving $F=mg$. Dividing mass by gravitational acceleration does not express the weight-force relation.

5. If the separation between two bodies doubles while their masses remain unchanged, what happens to their gravitational force?

A. It becomes half as large, because force varies inversely with separation

B. It remains unchanged, because force depends on mass but not separation

C. It becomes twice as large, because force increases with separation

D. It becomes one quarter as large, because force varies inversely with the square of separation

Answer: (D)

Explanation

Newton’s gravitational relation makes force proportional to the product of the masses and inversely proportional to the square of their separation. Doubling the separation therefore reduces the force to one quarter, rather than one half.

6. Which relation expresses Einstein’s mass–energy equivalence?

A. $F=k\frac{m_1m_2}{r^2}$

B. $E=\frac{mv^2}{2}$

C. $E=mc^2$

D. $F=mg$

Answer: (C)

Explanation

Einstein’s mass–energy relation states that energy equals mass multiplied by the square of the speed of light, $E=mc^2$. The expression with velocity squared and a factor of one half gives kinetic energy instead.

7. A sample has uniform composition and consists of a single kind of matter; how is it classified?

A. As a homogeneous substance

B. As a pure substance with necessarily changing composition

C. As a heterogeneous substance

D. As a mixture in variable proportions

Answer: (A)

Explanation

A homogeneous substance consists of a single kind of matter and has uniform composition. A heterogeneous substance, by contrast, contains more than one kind of matter.

8. A rock contains visible quartz, feldspar, and mica; what does this indicate about the rock?

A. It is homogeneous because its components form one solid object

B. It is heterogeneous because it contains multiple kinds of matter

C. It is a variable-proportion mixture whose components have lost their properties

D. It is a pure substance because its minerals have characteristic properties

Answer: (B)

Explanation

Granite is an example of a heterogeneous substance because it contains different kinds of matter, including quartz, feldspar, and mica. The fact that these components form one rock does not make its composition uniform.

9. What distinguishes a pure substance from a material whose composition varies from sample to sample?

A. It consists of several components that retain separate properties

B. It has a precisely defined, constant chemical composition and characteristic constant properties

C. It has a uniform appearance but no defined chemical composition

D. It contains multiple substances whose proportions vary between samples

Answer: (B)

Explanation

A pure substance has a precisely defined, constant chemical composition and characteristic constant properties. A material with components in variable proportions is a mixture, even if it appears uniform.

10. In a mixture, what happens to the component substances and their proportions?

A. Two or more substances occur in variable proportions, and each retains its characteristic properties

B. One kind of matter forms a uniform composition with no separate components

C. Two or more substances combine in fixed proportions and lose their characteristic properties

D. Multiple kinds of matter occur in variable proportions, but their properties become identical

Answer: (A)

Explanation

A mixture contains at least two substances in variable proportions, and each component retains its characteristic properties. Fixed composition and loss of component properties do not describe the defining behavior of mixtures.

11. During distillation of a liquid solution, which substances are collected as vapour is condensed?

A. The dissolved solid, while both liquid components remain behind

B. All components together, in the same proportions as the original solution

C. The less volatile substances, while more volatile substances remain behind

D. The more volatile substances, while less volatile substances remain behind

Answer: (D)

Explanation

Distillation collects the more volatile substances as vapour and leaves less volatile substances behind. The reverse description is a plausible mix-up, but it swaps which substances evaporate and which remain.

12. A mixture contains a soluble solid and an insoluble solid. Which sequence can separate the insoluble solid from the dissolved component and then recover the soluble solid?

A. Centrifuge the dry mixture, then condense the separated solids into crystals

B. Boil the mixture to separate the solids by boiling point, then condense both vapours

C. Dissolve the soluble component, filter out the insoluble solid, then crystallize the dissolved solid

D. Filter the dry mixture, then heat the residue until both solids evaporate

Answer: (C)

Explanation

Dissolving the soluble component allows filtration to separate the insoluble solid, and crystallization can recover the dissolved solid. Boiling-point separation is used for suitable liquids, not for separating two solids in a dry mixture.

13. Which set consists entirely of characteristic physical properties that can help describe a pure substance?

A. Aggregate state, reactivity, combustibility, melting point, density, and solubility

B. Color, odor, flammability, melting point, boiling point, and solubility

C. Color, odor, aggregate state, corrosion, boiling point, and chemical stability

D. Color, odor, aggregate state, melting point, boiling point, and solubility

Answer: (D)

Explanation

Color, odor, aggregate state, melting point, boiling point, and solubility are characteristic physical properties. Flammability and reactivity, by contrast, describe chemical behavior rather than physical properties.

14. How is a chemical property of a pure substance determined?

A. By recording its melting point while it changes physical state

B. By observing a reaction that transforms it into another substance

C. By measuring its solubility while it remains chemically unchanged

D. By measuring its color and odor without changing its composition

Answer: (B)

Explanation

Chemical properties are determined through reactions that transform a substance into other substances. Measuring color or melting point can characterize physical properties without chemical transformation.

15. A pure substance cannot be broken down into simpler substances by chemical reactions. How is it classified?

A. As a solution, because its composition can vary between samples

B. As an element, because compounds can be decomposed into elements by chemical reactions

C. As a compound, because elements can be decomposed into simpler substances by chemical reactions

D. As a mixture, because its components can be separated by physical methods

Answer: (B)

Explanation

An element cannot be decomposed into other substances by chemical reactions, whereas a compound can be decomposed into elements. The compound description reverses this defining distinction.

16. What happens during the chemical process called synthesis?

A. A mixture separates into components through filtration

B. Elements combine chemically to form a compound

C. A compound decomposes chemically into its constituent elements

D. A liquid solution separates according to boiling point

Answer: (B)

Explanation

Synthesis is the chemical combination of elements to form a compound. Decomposing a compound into elements is analysis, not synthesis.

17. Which statement best captures Robert Boyle’s early definition of an element in his 1661 book The Sceptical Chymist?

A. A substance made from simpler substances and decomposable into elements by reactions

B. A basic substance that cannot be decomposed into, or formed from, simpler substances

C. A mixture whose components can be separated by physical methods

D. A substance defined by having a fixed melting point and boiling point

Answer: (B)

Explanation

Boyle described an element as a basic substance that cannot be decomposed into simpler substances or formed from simpler substances. The decomposition-based description applies to compounds, not Boyle’s definition of an element.

18. Which statement reflects F. W. Clarke’s account of elements in Earth’s crust?

A. About 110 elements occur in the crust, and silicon alone makes up half of it

B. About 110 elements occur in the crust, and oxygen and silicon together make up half of it

C. Ninety-two elements occur in the crust, and oxygen and silicon together make up half of it

D. Ninety-two elements occur in the crust, and oxygen alone makes up half of it

Answer: (C)

Explanation

Clarke stated that 92 elements occur in Earth’s crust and that oxygen and silicon together account for half of it. The figure of about 110 refers to elements occurring in nature overall, not Clarke’s count for the crust.

19. In a chemical reaction, what does the law of conservation of mass state about the total mass of the substances involved?

A. It remains unchanged only when energy is included in the total.

B. It increases when atoms combine into new substances.

C. It remains unchanged between the reactants and products.

D. It decreases when chemical bonds are broken.

Answer: (C)

Explanation

The law states that the total mass of the substances involved in a reaction does not change. The energy-inclusive statement concerns a closed system retaining energy, not the reaction mass law itself.

20. A pure compound is prepared in several different batches. What relationship does Proust’s law predict between the masses of its constituent elements?

A. Their mass ratio varies with the amount of compound made.

B. Their masses are equal whenever the compound is pure.

C. Their mass ratio consists of small whole numbers in every compound.

D. Their mass ratio is constant from batch to batch.

Answer: (D)

Explanation

Proust’s law says that a given compound contains its elements in a constant mass ratio. Small whole-number ratios of element masses across multiple compounds describe Dalton’s law of multiple proportions instead.

21. Two elements form several compounds. If the mass of one element is held fixed, what does Dalton’s law of multiple proportions predict about the masses of the other element?

A. They occur in ratios of small whole numbers.

B. They are equal in each compound.

C. They remain in the same ratio in every compound.

D. They vary without any simple numerical relationship.

Answer: (A)

Explanation

Dalton’s law predicts small whole-number ratios between the masses that combine with a fixed mass of the other element. A constant mass ratio in every compound is the law of constant proportions, which applies to a given compound.

22. How did Dalton’s atomic theory describe atoms during chemical reactions?

A. As particles that change into atoms of different elements.

B. As particles that split into smaller parts when compounds form.

C. As collections of matter created when new substances appear.

D. As extremely small particles that cannot be divided during the reaction.

Answer: (D)

Explanation

Dalton described atoms as extremely small particles that cannot be divided during chemical reactions. The idea that atoms split into smaller parts during compound formation conflicts with this description.

23. Under Dalton’s theory, how do atoms of the same element compare with atoms of a different element?

A. Atoms of the same element match in mass but differ in size and chemical properties; different elements match in those traits.

B. Atoms of the same element match in mass, size, and chemical properties; different elements differ in these traits.

C. Atoms of the same element differ in mass and size but match in chemical properties; different elements differ only in mass.

D. Atoms of the same element match in size and chemical properties but differ in mass; different elements differ only in size.

Answer: (B)

Explanation

Dalton’s theory treats atoms of the same element as identical in mass, size, and chemical properties, while those of different elements differ in these properties. The alternatives each incorrectly limit or alter which traits distinguish the atoms.

24. What does Dalton’s theory propose about the atoms in a compound?

A. It contains atoms of more than one element in fixed numbers for that compound.

B. It contains atoms of more than one element in proportions that vary from sample to sample.

C. It contains atoms that lose their elemental identities when they form a compound.

D. It contains atoms of one element in changing numbers as the sample grows.

Answer: (A)

Explanation

Dalton’s theory states that compounds contain atoms of more than one element, with a fixed number of each element’s atoms in each compound. The idea that those numbers vary from sample to sample contradicts the fixed composition described by the theory.

25. When a chemical reaction occurs in Dalton’s theory, what happens to the atoms?

A. They divide into smaller particles before combining into products.

B. They are created as products form and destroyed as reactants disappear.

C. They separate, combine, or rearrange without being created or destroyed.

D. They remain in the same combinations while the substances change around them.

Answer: (C)

Explanation

Dalton’s theory describes reactions as the separation, combination, or rearrangement of atoms, with no atoms created or destroyed. The creation and destruction of atoms is a common confusion but is not part of this account of chemical reactions.

26. At constant temperature and pressure, what relationship does Gay-Lussac’s law describe among volumes of reacting gases and gaseous products?

A. They vary continuously with the amounts of the substances.

B. They are equal whenever the gases react completely.

C. They are in constant mass ratios for each compound.

D. They are in ratios of small whole numbers.

Answer: (D)

Explanation

Gay-Lussac’s law states that reacting or produced gas volumes have ratios of small whole numbers when temperature and pressure are constant. Constant mass ratios describe compound composition, not the gas-volume relationship in this law.

27. When hydrogen and oxygen react to produce water vapour, what gas-volume ratio does the stated example give for hydrogen, oxygen, and water vapour, respectively?

A. 1:2:2

B. 2:2:1

C. 3:1:2

D. 2:1:2

Answer: (D)

Explanation

The example gives two volumes of hydrogen reacting with one volume of oxygen to produce two volumes of water vapour. The ratio 1:2:2 instead reverses the hydrogen and oxygen volumes.