Question 1

Which of the following statements best describes an element?

Accepted Answer

An element is a substance that cannot be broken down into simpler substances by ordinary chemical means.

Question 2

Which four elements make up approximately 96% of the mass of living organisms?

Accepted Answer

Carbon, Hydrogen, Nitrogen, Oxygen

Question 3

A molecule of glucose (C6H12O6) contains how many atoms in total?

Accepted Answer

$$6 + 12 + 6 = 24$$

Question 4

Which of the following best describes a compound?

Accepted Answer

A compound contains atoms of two or more different elements combined in a fixed ratio.

Question 5

What is the atomic number of an atom with 7 protons, 7 neutrons, and 7 electrons?

Accepted Answer

$$7$$

Question 6

Which subatomic particle determines the chemical properties of an atom?

Accepted Answer

Electron

Question 7

If an atom has an atomic mass of 23 and an atomic number of 11, how many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$

Question 8

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 9

Radioactive isotopes are useful in biology for all of the following EXCEPT:

Accepted Answer

Increasing the stability of proteins

Question 10

What is the half-life of a radioactive isotope?

Accepted Answer

The time required for half of a sample to decay into a more stable form

Question 11

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

Accepted Answer

Covalent bond

Question 12

What is the main reason water is a polar molecule?

Accepted Answer

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

Question 13

Which property of water allows it to move upward through the vessels of plants against gravity?

Accepted Answer

Cohesion and adhesion

Question 14

A solution with a pH of 4 has how many times more hydrogen ions ($$[H^+]) $$than a solution with a pH of 7?

Accepted Answer

$$10^3 = 1000$

Question 15

Which of the following best describes a buffer?

Accepted Answer

A substance that minimizes changes in pH by accepting or donating $$H^+$$ ions

Question 16

Ocean acidification is primarily caused by which of the following processes?

Accepted Answer

Absorption of $$CO_2$$ from the atmosphere by seawater

Question 17

Which of the following is a real-world consequence of acid precipitation?

Accepted Answer

Soil acidification can increase the solubility of toxic ions like aluminum

Question 18

Which of the following best explains why carbon dating is not useful for dating dinosaur fossils?

Accepted Answer

The half-life of carbon-14 is too short to date fossils millions of years old

Question 19

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weaker than covalent and ionic bonds but can collectively provide significant force

Question 20

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

Accepted Answer

A molecule is formed by covalent bonds and may consist of the same or different elements, while a compound must contain different elements in a fixed ratio.

The Chemical Basis of Life: Matter, Elements, and Atomic Structure

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