$$6 \times 12 + 12 \times 1 + 6 \times 16 = 180$$

Question 1

Which element makes up the largest percentage of the human body by mass, and why is it so abundant?

Accepted Answer

Oxygen, because it is a major component of water and is required for cellular respiration.

Question 2

A student observes the electrolysis of water, as shown in the diagram. Which equation correctly represents the chemical reaction occurring?

Accepted Answer

$$2 \mathrm{H}_2\mathrm{O} \rightarrow 2 \mathrm{H}_2 + \mathrm{O}_2$$

Question 3

Which of the following best describes the difference between an element and a compound?

Accepted Answer

An element is a pure substance made of atoms, while a compound is a substance made of two or more elements in a fixed ratio.

Question 4

Which property of water is most directly responsible for the phenomenon of capillary action in plants?

Accepted Answer

Cohesion and adhesion

Question 5

A sodium atom (Na) reacts with a chlorine atom (Cl) to form sodium chloride (NaCl). What type of bond is formed, and what happens to the electrons?

Accepted Answer

Ionic bond; Na transfers an electron to Cl, resulting in electrostatic attraction.

Question 6

Which equation correctly calculates the molecular weight of glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$)?

Accepted Answer

$$6 	imes 12 + 12 	imes 1 + 6 	imes 16 = 180$$

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 8

Which functional group is responsible for the acidic properties of organic acids?

Accepted Answer

Carboxyl group ($$-\mathrm{COOH})$$

Question 9

Which property of water allows ice to float on liquid water, and why is this important for life?

Accepted Answer

Water's lower density as a solid; ice insulates aquatic life below.

Question 10

Which equation correctly expresses the relationship between pH and hydrogen ion concentration?

Accepted Answer

$$\mathrm{pH} = -\log[\mathrm{H}^+]$$

Question 11

Which of the following best explains why carbon is the basis of organic chemistry?

Accepted Answer

Carbon can form four stable covalent bonds, allowing for diverse structures.

Question 12

Which of the following is NOT a function of proteins in living organisms?

Accepted Answer

Energy storage

Question 13

Which property of water is most important for moderating Earth's climate?

Accepted Answer

Water's high heat capacity

Question 14

Which of the following best describes the difference between starch and cellulose?

Accepted Answer

Starch is a polymer of $$\alpha-$$glucose, while cellulose is a polymer of $$\beta-$$glucose.

Question 15

Which of the following is a correct statement about the octet rule?

Accepted Answer

Atoms are most stable when their outer shell contains eight electrons.

Question 16

Which of the following is a real-world example of a polar covalent bond?

Accepted Answer

The bond between hydrogen and oxygen in H$$_2O$$

Question 17

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weaker than ionic bonds.

Question 18

Which of the following is a correct statement about the structure of DNA?

Accepted Answer

DNA is a double helix held together by hydrogen bonds between complementary bases.

Question 19

Which of the following is a correct application of the conservation of matter in a chemical reaction?

Accepted Answer

The number of atoms in the reactants equals the number of atoms in the products.

Unit 2

Study Guide - Practice Questions