Q: Which of the following best describes Avogadro's number?

It is the number of atoms or molecules in one mole, $$6.02 \times 10$$^{23}$$.

Question 1

Which of the following statements best describes the difference between an atom and an ion?

Accepted Answer

An atom has an equal number of protons and electrons, while an ion has an unequal number of protons and electrons.

Question 2

A neutral atom of carbon-14 has an atomic number of 6 and a mass number of 14. How many neutrons does it have?

Accepted Answer

$$14 - 6 = 8$$ neutrons

Question 3

Which of the following best explains why atoms with a full valence shell are generally unreactive?

Accepted Answer

Their outermost electron shell is filled, so they do not tend to gain, lose, or share electrons.

Question 4

Which of the following is an example of a polar covalent bond?

Accepted Answer

The bond between oxygen and hydrogen in a water molecule ($$\mathrm{H_2O})$$

Question 5

Which of the following best describes Avogadro's number?

Accepted Answer

It is the number of atoms or molecules in one mole, $$6.02 	imes 10$$^{23}$$.

Question 6

A student dissolves table salt ($$\mathrm{NaCl}) in $$water. Which type of bond is broken in the salt, and what type of interaction forms between the ions and water molecules?

Accepted Answer

Ionic bonds are broken; ion-dipole interactions (hydration) form between ions and water.

Question 7

Which of the following best describes a redox reaction?

Accepted Answer

A chemical reaction in which one substance loses electrons (is oxidized) and another gains electrons (is reduced).

Question 8

In the rusting of iron, which element is reduced and what does this mean in terms of electron movement?

Accepted Answer

Oxygen is reduced; it gains electrons.

Question 9

Which of the following best explains why moles are used in chemistry instead of just mass?

Accepted Answer

Moles allow chemists to count numbers of atoms or molecules, which is necessary because chemical reactions occur between particles, not masses.

Question 10

Which of the following is a correct chemical equation showing equilibrium?

Accepted Answer

$$\mathrm{$$CaCO_3$$ (s) \rightleftharpoons CaO (s) + CO_2$ (g)}$$

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak interaction between a partially positive hydrogen atom and a partially negative atom (such as oxygen or nitrogen) in another molecule.

Question 12

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which of the following best describes a molecule?

Accepted Answer

A group of two or more atoms held together by covalent bonds.

Question 14

Which of the following is a compound but not a molecule?

Accepted Answer

Sodium chloride ($$\mathrm{NaCl})$$

Question 15

Which of the following best describes a cation?

Accepted Answer

An ion with a positive charge, formed when an atom loses one or more electrons.

Question 16

Which of the following best explains why water is a good solvent for ionic compounds?

Accepted Answer

Water is polar, so its partial charges can surround and stabilize ions.

Question 17

Which of the following statements about chemical equilibrium is correct?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 18

Which of the following is the best example of a nonpolar covalent bond?

Accepted Answer

The bond between two oxygen atoms in $$\mathrm{O_2$}$$

Question 19

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of glucose ($$\mathrm{C_6H_{12}$$O_6$$}$$). How many moles of glucose are present?

Accepted Answer

$$0.5$$ moles

Question 20

Which of the following best describes the relationship between oxidation and reduction in a redox reaction?

Accepted Answer

Oxidation and reduction always occur together; when one substance is oxidized, another is reduced.

Chapter 2 Notes

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