Q: A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-4}$$ \ \mathrm{M}$$

Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice cause water molecules to be less densely packed than in liquid water.

Question 2

A nitrogen atom has 7 protons and its most common isotope has 7 neutrons. What is the atomic number and mass number of a radioactive isotope of nitrogen with 9 neutrons?

Accepted Answer

Atomic number: 7, Mass number: 16

Question 3

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions rearrange matter by breaking and forming chemical bonds.

Question 4

Which property of water allows it to moderate Earth's climate by absorbing and releasing heat with only slight temperature changes?

Accepted Answer

Water's high specific heat due to hydrogen bonding

Question 5

What is the main reason that water is such a versatile solvent?

Accepted Answer

Water molecules are polar, allowing them to surround and dissolve ionic and polar substances.

Question 6

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between atoms.

Question 7

A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ \ \mathrm{M}$$

Question 8

Which of the following is a trace element that is commonly added to municipal water supplies to prevent tooth decay?

Accepted Answer

Fluoride

Question 9

What is the primary effect of ocean acidification on coral reefs?

Accepted Answer

It reduces the concentration of carbonate ions, slowing the growth of coral skeletons.

Question 10

Which of the following best describes the difference between adhesion and cohesion in water?

Accepted Answer

Cohesion is the attraction between water molecules; adhesion is the attraction between water and other substances.

Question 11

Which of the following is an example of an ionic bond?

Accepted Answer

The bond between sodium and chlorine in table salt ($$\mathrm{NaCl}).$$

Question 12

Which of the following best explains why sweating cools your body?

Accepted Answer

Sweat absorbs heat as it evaporates, carrying thermal energy away from the skin.

Question 13

Which of the following is true about isotopes?

Accepted Answer

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

Question 14

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 15

A scientist is studying the effect of carbonate ion concentration on the rate of calcium deposition by coral. In this experiment, what is the independent variable?

Accepted Answer

The concentration of carbonate ions

Question 16

Which of the following equations correctly represents the reaction of carbon dioxide with water that leads to ocean acidification?

Accepted Answer

$$\mathrm{CO_2$} + \mathrm{H_2O} \rightarrow \mathrm{H_2CO_3}$$

Question 17

Which of the following best explains why salt ($$\mathrm{NaCl}) $$dissolves easily in water?

Accepted Answer

The positive and negative ends of water molecules surround and separate the sodium and chloride ions.

Question 18

Which of the following is NOT a life-supporting property of water?

Accepted Answer

Water is a good solvent for nonpolar substances.

Question 19

If a solution changes from pH 7 to pH 5, how does the hydrogen ion concentration change?

Accepted Answer

It increases by a factor of 100.

Question 20

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating hydrogen ions.

The Chemical Basis of Life: Elements, Atoms, and Compounds

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