$$\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more different elements combined in a fixed ratio.

Question 2

Which subatomic particle is responsible for the chemical properties of an atom?

Accepted Answer

Electron

Question 3

What is the atomic mass of an element with 6 protons, 6 neutrons, and 6 electrons?

Accepted Answer

$$12$$

Question 4

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, creating a partial negative charge near the oxygen atom.

Question 5

Which equation correctly represents the calculation of atomic mass?

Accepted Answer

$$	ext{Atomic mass} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 6

Which of the following is a trace element essential for human health?

Accepted Answer

Iron

Question 7

A radioactive isotope is best described as an atom that:

Accepted Answer

Has an unstable nucleus that decays over time, emitting radiation.

Question 8

Which type of bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 9

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Question 10

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

Accepted Answer

The bond between two hydrogen atoms in $$H_2$$

Question 11

Which of the following best explains why salt ($$NaCl) $$dissolves in water?

Accepted Answer

Water's polarity allows it to surround and separate the positive sodium ions and negative chloride ions.

Question 12

Which equation represents the relationship between energy, mass, and the speed of light?

Accepted Answer

$$E = mc^2$

Question 13

Which of the following best describes a buffer in a biological system?

Accepted Answer

A substance that minimizes changes in pH by accepting or donating hydrogen ions.

Question 14

Which of the following is an example of a colligative property?

Accepted Answer

Boiling point elevation

Question 15

Which of the following best explains why ice floats on water?

Accepted Answer

Hydrogen bonds in ice create a lattice that is less dense than liquid water.

Question 16

Which of the following is the best definition of electronegativity?

Accepted Answer

The ability of an atom to attract electrons in a covalent bond.

Question 17

Which of the following is a correct statement about van der Waals interactions?

Accepted Answer

They are weak attractions between molecules due to temporary partial charges.

Question 18

Which of the following best describes the role of surface tension in water?

Accepted Answer

It enables small insects to walk on water due to cohesive forces between water molecules.

Question 19

Which of the following is the best example of a hydration shell?

Accepted Answer

A layer of water molecules surrounding a dissolved ion.

Question 20

Which of the following equations represents the calculation of molarity?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

The Chemical Context of Life: Atoms, Bonds, and Water

Study Guide - Practice Questions