Question 1

Which of the following best describes an element?

Accepted Answer

A substance that cannot be broken down to other substances by chemical means.

Question 2

What is the atomic number of an atom?

Accepted Answer

The number of protons in its nucleus.

Question 3

A radioactive isotope of carbon decays by releasing a neutron from its nucleus. What is the result of this decay?

Accepted Answer

The atom remains carbon but has a different number of neutrons.

Question 4

Which of the following best explains why water has a high heat of vaporization?

Accepted Answer

Water molecules are held together by hydrogen bonds, requiring a large amount of energy to separate them.

Question 5

Which statement about covalent bonds is correct?

Accepted Answer

Covalent bonds involve the sharing of valence electrons between atoms.

Question 6

A solution has a pH of 4. Which of the following statements is true?

Accepted Answer

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

Question 7

Which of the following is a consequence of the octet rule in chemical bonding?

Accepted Answer

Atoms attempt to fill their valence shell with 8 electrons by sharing, gaining, or losing electrons.

Question 8

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond between a partial positive charge on a hydrogen atom and a partial negative charge on another atom.

Question 9

If a molecule of sodium hydroxide ($$\mathrm{NaOH}) is $$added to water, what happens to the concentration of hydroxide ions ($$\mathrm{OH^-}) $$and the pH of the solution?

Accepted Answer

Hydroxide ion concentration increases and pH increases.

Question 10

Which property of water allows lakes and ponds to remain liquid under a layer of ice during winter?

Accepted Answer

Ice is less dense than liquid water, so it floats and insulates the water below.

Question 11

Which of the following is true about acids and bases in aqueous solutions?

Accepted Answer

Acids release $$\mathrm{H^+}$$ ions and bases release $$\mathrm{OH^-}$$ ions.

Question 12

A molecule with the formula $$\mathrm{C_6H_{12}O_6$} is $$dissolved in water. What type of solution is formed?

Accepted Answer

An aqueous solution.

Question 13

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

Accepted Answer

Water has an unequal sharing of electrons, resulting in partial charges on the oxygen and hydrogen atoms.

Question 14

What happens to the structure of biological molecules when the pH of their environment changes drastically?

Accepted Answer

Their 3-dimensional structure can be denatured.

Question 15

Which of the following is a weak chemical interaction important for biological recognition?

Accepted Answer

Hydrogen bond

Question 16

A solution has a pH of 9. What is the concentration of hydrogen ions ($$[\mathrm{H^+}]) $$compared to a solution with pH 7?

Accepted Answer

$$[\mathrm{H^+}] is 100 $$times lower in the pH 9 solution.

Question 17

Which of the following is true about ions?

Accepted Answer

Cations are positively charged and anions are negatively charged.

Question 18

Which of the following best describes the role of a solvent in a solution?

Accepted Answer

The solvent is the substance that dissolves the solute.

Question 19

Which of the following is a real-world example of a chemical reaction involving reactants and products?

Accepted Answer

Burning glucose ($$\mathrm{C_6H_{12}O_6$}) in $$oxygen to produce carbon dioxide and water.

Atoms, Elements, and the Chemical Basis of Life: Study Notes

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