Q: A solution has a pH of 4. What is the hydrogen ion concentration $$[H^+] in $$moles per liter?

$$[H^+] = 10$$^{-4}$$ \text{ M}$$

Question 1

Which of the following best explains why ice floats on liquid water, and why this property is important for aquatic life?

Accepted Answer

Ice is less dense than liquid water due to the formation of a crystalline lattice by hydrogen bonds, which allows ice to float and insulate the water below, protecting aquatic life from freezing.

Question 2

A patient is diagnosed with goiter, a swelling of the thyroid gland. Which trace element deficiency is most likely responsible for this condition?

Accepted Answer

Iodine

Question 3

Which of the following statements about covalent bonds is correct?

Accepted Answer

A double covalent bond involves the sharing of two pairs of electrons between atoms.

Question 4

Which equation correctly represents the relationship between pH and hydrogen ion concentration $$[H^+]$$?

Accepted Answer

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

Question 5

A radioactive isotope is used in a PET scan to diagnose cancer. What property of radioactive isotopes makes them useful for this application?

Accepted Answer

They emit particles and energy as they decay, which can be detected by imaging equipment.

Question 6

Which of the following best describes the difference between a cation and an anion?

Accepted Answer

A cation is a positively charged ion, while an anion is a negatively charged ion.

Question 7

Which property of water allows it to moderate Earth's climate and stabilize temperatures in organisms?

Accepted Answer

High specific heat

Question 8

A solution has a pH of 4. What is the hydrogen ion concentration $$[H^+] in $$moles per liter?

Accepted Answer

$$[H^+] = 10$$^{-4}$$ 	ext{ M}$$

Question 9

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are hydrophobic due to their nonpolar covalent bonds, which do not interact favorably with water's polar molecules.

Question 10

Which of the following is an example of a chemical reaction?

Accepted Answer

The conversion of sodium and chlorine to sodium chloride: $$2Na + Cl_2$ \rightarrow 2NaCl$$

Question 11

A buffer solution is added to a beaker of water. What is the primary function of the buffer?

Accepted Answer

To minimize changes in the concentrations of $$H^+$$ and $$OH^-$$ ions when acids or bases are added.

Question 12

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are found in the outermost shell and determine the chemical reactivity and bonding behavior of an atom.

Question 13

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity is an atom’s attraction for the electrons in a covalent bond.

Question 14

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water’s polarity allows it to surround and separate ions, forming hydration shells.

Question 15

A gecko can climb smooth walls due to van der Waals interactions. What is the nature of these interactions?

Accepted Answer

They are weak attractions that occur when electrons are distributed asymmetrically in molecules or atoms, allowing temporary regions of positive and negative charge.

Question 16

Which of the following is true about chemical equilibrium in a reversible reaction?

Accepted Answer

The forward and reverse reaction rates are equal, so the concentrations of reactants and products remain constant.

Question 17

Which of the following best describes the difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

In a polar covalent bond, electrons are shared unequally, resulting in partial charges; in a nonpolar covalent bond, electrons are shared equally.

Question 18

A solution is made by dissolving 1 mole of glucose ($$C_6H_{12}O_6$) in enough water to make 1 liter of solution. What is the molarity (M) of the solution?

Accepted Answer

1 M

Question 19

Which property of water is most responsible for the upward movement of water in plants against gravity?

Accepted Answer

Cohesion due to hydrogen bonding

Question 20

Which of the following best describes the effect of ocean acidification on marine organisms?

Accepted Answer

It reduces the availability of carbonate ions, making it harder for organisms to form shells and skeletons.

Chapter 2: The Chemical Context of Life – Study Notes

Study Guide - Practice Questions

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