Question 1

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

Accepted Answer

An element is a substance made of only one type of atom, while a compound consists of two or more different elements chemically bonded together.

Question 2

A neutral atom of sodium ($ \mathrm{Na} $) has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

12

Question 3

Which of the following best explains why water is an excellent solvent for many biological molecules?

Accepted Answer

Water is a polar molecule, allowing it to form hydrogen bonds with ions and other polar molecules.

Question 4

A scientist is testing the effect of a new fertilizer on plant growth. She sets up two groups: one receives the fertilizer, and the other does not. What is the independent variable in this experiment?

Accepted Answer

Whether or not the plants receive fertilizer

Question 5

Which of the following statements about covalent and ionic bonds is correct?

Accepted Answer

Covalent bonds involve the sharing of electrons, while ionic bonds involve the transfer of electrons from one atom to another.

Question 6

Given the electronegativities: $ \mathrm{H} = 2.1 $, $ \mathrm{O} = 3.5 $, $ \mathrm{C} = 2.5 $, which bond is most polar?

Accepted Answer

$ \mathrm{O-H} $

Question 7

A solution has a hydrogen ion concentration of $ 1 	imes 10^{-4} $ M. What is its pH?

Accepted Answer

4

Question 8

Which of the following best describes a controlled variable in a scientific experiment?

Accepted Answer

A factor that is kept constant to ensure that the effect of the independent variable can be measured accurately.

Question 9

Which property of water allows insects such as water striders to walk on its surface?

Accepted Answer

High surface tension due to hydrogen bonding between water molecules.

Question 10

A molecule of methane ($ \mathrm{CH}_4 $) is nonpolar. Which statement best explains why?

Accepted Answer

The molecule is symmetrical, so the polarities of the C-H bonds cancel out.

Question 11

Which of the following substances would you expect to dissolve readily in water?

Accepted Answer

Sodium chloride ($ \mathrm{NaCl} $)

Question 12

If a solution has a pH of 2, which of the following statements is true?

Accepted Answer

The solution has a high concentration of hydrogen ions and is acidic.

Question 13

Which of the following best describes how hydrogen bonds form between water molecules?

Accepted Answer

A hydrogen atom with a partial positive charge is attracted to an oxygen atom with a partial negative charge on a neighboring molecule.

Question 14

Which of the following is a correct prediction about the number of covalent bonds an oxygen atom (atomic number 8) can form?

Accepted Answer

2, because oxygen has 6 valence electrons and needs 2 more to fill its outer shell.

Question 15

A student is given a graph showing the growth of two bacterial populations over time, one exposed to an antibiotic and one not exposed. What is the most reasonable conclusion if the exposed population declines while the unexposed population increases?

Accepted Answer

The antibiotic inhibits the growth of the bacteria.

Question 16

Which of the following best explains why salt (NaCl) dissolves in water but oil does not?

Accepted Answer

Salt is ionic and interacts with water's partial charges, while oil is nonpolar and cannot form hydrogen bonds with water.

Question 17

Which of the following is the best definition of a hypothesis in the scientific method?

Accepted Answer

A testable explanation for an observation or scientific problem.

Question 18

If a molecule has a region with a partial positive charge and another with a partial negative charge, what type of bond is most likely present?

Accepted Answer

Polar covalent bond

Question 19

A patient is diagnosed with acidosis, meaning their blood pH is below 7.35. Which of the following best describes the hydrogen ion concentration in their blood compared to normal?

Accepted Answer

It is higher than normal, making the blood more acidic.

General Biology: Foundations, Scientific Method, and Chemistry of Life

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