Question 1

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

Accepted Answer

Because the oxygen atom is more electronegative than the hydrogen atoms, creating partial charges.

Question 2

Which type of bond is shown between the two hydrogen atoms in the H$$_2$$ molecule (see image 1)?

Accepted Answer

Nonpolar covalent bond

Question 3

A lime (see image 2) tastes sour because it contains citric acid. Which of the following statements about acids is correct?

Accepted Answer

Acids donate H$$^+$$ ions to a solution, lowering the pH.

Question 4

Given the electronegativity scale (see image 3), what type of bond would you expect between sodium (Na, 0.93) and chlorine (Cl, 3.16)?

Accepted Answer

Ionic bond

Question 5

Which property of water allows it to moderate temperature changes in coastal cities compared to inland cities?

Accepted Answer

High specific heat

Question 6

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice are stable and hold molecules apart, making ice less dense.

Question 7

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between a partially positive hydrogen and a partially negative atom like O or N

Question 8

Which of the following molecules would be hydrophobic?

Accepted Answer

A nonpolar molecule such as methane (CH$$_4)$$

Question 9

If the concentration of hydrogen ions in a solution is $$1 	imes 10$$^{-4}$$ M, what is the pH of the solution?

Accepted Answer

$$4$$

Question 10

A solution with a pH of 5 has how many times more hydrogen ions than a solution with a pH of 7?

Accepted Answer

100 times more

Question 11

Which of the following is NOT a property of water that results from hydrogen bonding?

Accepted Answer

Water is a good solvent for nonpolar molecules

Question 12

Which of the following best explains why salt (NaCl) dissolves in water?

Accepted Answer

The partial negative charge on oxygen in water surrounds Na$$^+$$, and the partial positive charge on hydrogen surrounds Cl$$^-.$$

Question 13

Which of the following statements about hydrogen bonds in DNA is correct?

Accepted Answer

Hydrogen bonds hold the two strands of DNA together between complementary bases.

Question 14

Which of the following best describes the relationship between pH and [H$$^+$$]?

Accepted Answer

As [H$$^+$$] increases, pH decreases.

Question 15

Which of the following is an example of an emergent property of water?

Accepted Answer

Surface tension

Question 16

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

Accepted Answer

They cannot form hydrogen bonds with water.

Question 17

Which of the following is true about the bond between oxygen and hydrogen within a water molecule?

Accepted Answer

It is a polar covalent bond.

Question 18

A buffer is important in biological systems because it:

Accepted Answer

Resists changes in pH when acids or bases are added.

Question 19

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

Accepted Answer

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

Question 20

Which of the following is true about the pH of pure water?

Accepted Answer

It is neutral, with [H$$^+$$] = [OH$$^-$$] and pH = 7.

Water: Structure, Properties, and Biological Importance

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