Q: A solution has a hydrogen ion concentration of $$[H^+] = 1 \times 10$$^{-5}$$ M. What is its pH?

$$pH = -\log_{10}(1 \times 10$$^{-5}$$) = 5$$

Question 1

Which of the following best describes an emergent property of a compound?

Accepted Answer

A property that arises only when elements are combined in a fixed ratio, and is not present in the individual elements.

Question 2

A sodium atom has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

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

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

High specific heat

Question 5

A patient is injected with a radioactive isotope for a PET scan. Which property of the isotope is most important for this medical application?

Accepted Answer

It decays spontaneously, emitting particles and energy that can be detected.

Question 6

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

Accepted Answer

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

Question 7

Which of the following is a real-world consequence of ocean acidification caused by increased atmospheric $$CO_2$$?

Accepted Answer

Decreased availability of carbonate ions for shell-building organisms.

Question 8

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

$$pH = -\log_{10}(1 	imes 10$$^{-5}$$) = 5$$

Question 9

Which of the following best describes the difference between covalent and ionic bonds?

Accepted Answer

Covalent bonds involve sharing of electrons, while ionic bonds involve transfer of electrons.

Question 10

Which property of water is most directly responsible for the ability of some insects to walk on water?

Accepted Answer

Surface tension due to hydrogen bonding

Question 11

A buffer solution contains carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). What happens when a small amount of acid is added to this solution?

Accepted Answer

The bicarbonate ion ($$HCO_3$$^-$$) acts as a base and neutralizes the added acid.

Question 12

Which of the following best explains why oil does not mix with water?

Accepted Answer

Oil molecules are nonpolar and hydrophobic, so they do not form hydrogen bonds with water.

Question 13

If a molecule has a high electronegativity, what effect does this have on a covalent bond it forms with hydrogen?

Accepted Answer

The bond will be polar, with the more electronegative atom having a partial negative charge.

Question 14

Which of the following is an example of a weak chemical interaction important in biological systems?

Accepted Answer

Hydrogen bonds between water molecules

Question 15

A beaker contains 1 liter of a 1 M NaCl solution. How many moles of NaCl are present?

Accepted Answer

1 mole

Question 16

Which of the following best describes the role of water in the transport of nutrients in plants?

Accepted Answer

Cohesion and adhesion allow water to move upward through plant vessels against gravity.

Question 17

Which of the following equations correctly represents the dissociation of water?

Accepted Answer

$$H_2O \rightleftharpoons H^+ + OH^-$$

Question 18

A solution has a pH of 3. How does its hydrogen ion concentration compare to a solution with pH 6?

Accepted Answer

It is 1,000 times higher.

Question 19

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

Accepted Answer

Evaporation of water from the skin absorbs heat due to water's high heat of vaporization.

Question 20

Which of the following is a direct consequence of the polarity of water molecules?

Accepted Answer

Water forms hydrogen bonds with other polar molecules.

Chapter 2: The Chemical Context of Life – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard