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

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

Question 1

Which of the following statements best describes the difference between an element and a compound?

Accepted Answer

An element is a substance that cannot be broken down by chemical reactions, while a compound consists of two or more elements combined in a fixed ratio.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in radiometric dating. If the atomic number of carbon is 6, how many neutrons does $$^{14}C$$ have?

Accepted Answer

$$8$$

Question 3

Which property of water allows it to move up a plant stem against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 4

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

Accepted Answer

Hydrogen bonds keep water molecules farther apart in ice, making it less dense than liquid water.

Question 5

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

Accepted Answer

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

Question 6

Which functional group is most likely to act as a base and accept a hydrogen ion in solution?

Accepted Answer

Amino group ($$-NH_2$)

Question 7

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetals

Question 8

Which of the following is an example of a structural isomer?

Accepted Answer

Pentane and 2-methyl butane

Question 9

Which property of water is primarily responsible for its ability to moderate temperature in living organisms?

Accepted Answer

High specific heat

Question 10

A buffer solution is important in biological systems because it:

Accepted Answer

Minimizes changes in pH when acids or bases are added

Question 11

Which of the following molecules is most likely to be hydrophobic?

Accepted Answer

A nonpolar molecule such as a fat

Question 12

Which of the following best describes the relationship between atomic number ($$Z$$), mass number ($$A$$), and number of neutrons ($$N$$)?

Accepted Answer

$$A = Z + N$$

Question 13

Which type of chemical bond is the strongest under physiological conditions?

Accepted Answer

Covalent bond

Question 14

Which of the following is a real-world application of radioactive isotopes in biology?

Accepted Answer

Dating fossils using radiometric techniques

Question 15

Which of the following best explains why water is considered the 'universal solvent'?

Accepted Answer

Its polarity allows it to dissolve many polar and ionic substances

Question 16

Which of the following functional groups is found in all amino acids and is responsible for their acidic properties?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 17

Which of the following statements about isomers is correct?

Accepted Answer

Enantiomers are mirror images of each other and may have different biological activities.

Question 18

A hydrocarbon with only single bonds will have what geometry around each carbon atom?

Accepted Answer

Tetrahedral with bond angles close to $$109.5^\circ$$

Question 19

Which of the following best describes the effect of adding a strong acid to a buffered solution?

Accepted Answer

The pH will change only slightly because the buffer will absorb the excess $$H^+$$ ions.

Question 20

Which of the following best explains why nonpolar molecules such as fats do not dissolve in water?

Accepted Answer

They are hydrophobic and do not interact favorably with water's polar molecules.

The Chemical Context of Life: Atoms, Water, and Carbon

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