$$C_6H_{12}O_6$ + 6 O_2$ \rightarrow 6 CO_2$ + 6 H_2O + \text{Energy}$$

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more elements in a fixed ratio, held together by chemical bonds.

Question 2

Which four elements make up approximately 96% of the human body’s mass?

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 3

An atom of sodium (Na) has 11 protons and 12 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: 11, Mass number: 23

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 5

A radioactive isotope of carbon, $$^{14}C$$, decays over time. Which property makes it radioactive?

Accepted Answer

It has an unstable nucleus that spontaneously emits particles and energy.

Question 6

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

Accepted Answer

Covalent bond

Question 7

What is the main difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

In a polar covalent bond, electrons are shared unequally due to differences in electronegativity.

Question 8

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons.

Question 9

Sodium (Na) and chlorine (Cl) react to form sodium chloride (NaCl). What type of bond is formed between Na and Cl in NaCl?

Accepted Answer

Ionic bond

Question 10

Which of the following best describes a hydrogen bond?

Accepted Answer

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

Question 11

Which of the following equations represents the process of cellular respiration?

Accepted Answer

$$C_6H_{12}O_6$ + 6 O_2$ ightarrow 6 CO_2$ + 6 H_2O + 	ext{Energy}$$

Question 12

A patient is injected with a radioactive isotope for medical imaging. Which property of the isotope allows it to be detected inside the body?

Accepted Answer

It emits radiation that can be detected by imaging equipment.

Question 13

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions involve the making and breaking of chemical bonds.

Question 14

If an atom has a valence shell that is not full, what is it most likely to do?

Accepted Answer

Form chemical bonds to achieve a full valence shell.

Question 15

Which of the following best explains why the shape of a molecule is important in biology?

Accepted Answer

The shape determines the molecule’s biological function and interactions.

Question 16

A scientist mixes two elements and observes the formation of a new substance with different properties. What has most likely occurred?

Accepted Answer

A chemical reaction has formed a compound.

Question 17

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

Accepted Answer

Iron (Fe)

Question 18

Which of the following best describes chemical equilibrium in a reversible reaction?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 19

Which of the following best explains why sodium (Na) forms a positive ion (Na$$^+) in $$ionic compounds?

Accepted Answer

Sodium loses one electron to achieve a full valence shell.

Question 20

Which of the following is the correct balanced equation for the formation of water from hydrogen and oxygen?

Accepted Answer

$$2 H_2$ + O_2$ \rightarrow 2 H_2O$$

The Chemical Context of Life: Foundations for General Biology

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