Question 1

Which of the following best explains why water is an effective solvent for ionic compounds such as sodium chloride (NaCl)?

Accepted Answer

Water is polar, so its partial positive and negative charges surround and stabilize the Na+ and Cl- ions, forming hydration shells.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used to date fossils. What property of $$^{14}C$$ makes it useful for this purpose?

Accepted Answer

It decays spontaneously, emitting particles and energy at a predictable rate.

Question 3

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weak attractions between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 4

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

Accepted Answer

Iodine (I)

Question 5

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of two or more different elements in a fixed ratio.

Question 6

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

Accepted Answer

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

Question 7

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

Accepted Answer

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

Question 8

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice are more 'ordered,' making ice less dense than liquid water.

Question 9

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

Accepted Answer

Hydrogen bonds between water molecules absorb heat when they break and release heat when they form, buffering temperature changes.

Question 10

A biologist wants to prepare 1 liter of a 0.5 M NaCl solution. The molecular mass of NaCl is 58.44 g/mol. How many grams of NaCl should be dissolved in water to make this solution?

Accepted Answer

29.22 g

Question 11

Which of the following is an example of a buffer system in human blood, and how does it function?

Accepted Answer

H_2CO_3/$$HCO_3$$^-, which can both donate and accept H^+ ions to minimize pH changes.

Question 12

Which of the following best describes the emergent properties of a compound?

Accepted Answer

They are new properties that arise from the specific arrangement and interactions of elements in the compound.

Question 13

Which of the following best explains why coastal areas tend to have milder climates than inland areas?

Accepted Answer

Water's high specific heat allows it to absorb and release large amounts of heat with little temperature change, moderating the climate.

Question 14

Which of the following statements about acids and bases is correct?

Accepted Answer

An acid increases the H^+ concentration, while a base decreases the H^+ concentration of a solution.

Question 15

A molecule of methane ($$CH_4) $$has which of the following shapes, and why?

Accepted Answer

Tetrahedral, because the four hydrogen atoms are spaced as far apart as possible around the central carbon.

Question 16

Which of the following best describes the process of evaporative cooling?

Accepted Answer

As water evaporates, the molecules with the highest kinetic energy leave, lowering the temperature of the remaining liquid.

Question 17

Which of the following best explains why a gecko can climb smooth vertical surfaces?

Accepted Answer

Van der Waals interactions between the gecko's toe hairs and the surface provide enough collective strength for adhesion.

Question 18

Which of the following is true about the relationship between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons; mass number is the sum of protons and neutrons.

Question 19

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

Accepted Answer

It decreases carbonate ion concentration, making it harder for organisms to build shells and coral reefs.

The Chemical Context of Life: Foundations for General Biology

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