Q: What is the correct formula for calculating the mass number of an atom?

$$\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$$

Q: A solution has a pH of 5. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-5}$$ \text{ M}$$

Question 1

Which of the following statements best explains why water is considered an excellent solvent for biological reactions?

Accepted Answer

Water's bent geometry and polar nature allow it to form hydrogen bonds with charged and polar molecules, facilitating their dissolution.

Question 2

A carbon atom has 6 protons and 8 neutrons. What is its mass number, and what is this form of carbon called?

Accepted Answer

Mass number is 14; this is carbon-14, a radioactive isotope.

Question 3

Which property of water allows it to move upward from the roots to the leaves in plants against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding.

Question 4

What is the correct formula for calculating the mass number of an atom?

Accepted Answer

$$	ext{Mass number} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 5

Why does ice float on liquid water?

Accepted Answer

Ice forms a relatively open crystal structure with hydrogen bonds, making it less dense than liquid water.

Question 6

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 7

A solution has a pH of 5. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-5}$$ 	ext{ M}$$

Question 8

Which of the following molecules would most likely dissolve in water?

Accepted Answer

A polar molecule such as glucose.

Question 9

What type of bond is formed when electrons are transferred from one atom to another, resulting in oppositely charged ions?

Accepted Answer

Ionic bond

Question 10

Which statement best describes the electron-sharing continuum in chemical bonds?

Accepted Answer

Electrons can be shared equally (nonpolar covalent), unequally (polar covalent), or transferred (ionic) depending on the atoms involved.

Question 11

Which of the following is true about acids and bases in water?

Accepted Answer

Acids increase the concentration of $$H_3O^+$$ ions, while bases decrease it.

Question 12

Which property of water is most responsible for its high specific heat?

Accepted Answer

The extensive hydrogen bonding between water molecules.

Question 13

If a molecule is described as hydrophobic, what does this mean regarding its interaction with water?

Accepted Answer

It does not dissolve in water and tends to aggregate with other nonpolar molecules.

Question 14

Which of the following best explains why living cells maintain a pH close to 7?

Accepted Answer

To maintain homeostasis and provide optimal conditions for biological processes.

Question 15

Which element is most likely to form four covalent bonds due to its number of unpaired electrons?

Accepted Answer

Carbon

Question 16

A molecule of ammonia ($$NH_3) is $$formed by nitrogen sharing electrons with three hydrogen atoms. What type of bond is present between nitrogen and hydrogen in ammonia?

Accepted Answer

Polar covalent bond

Question 17

Which of the following best describes the role of carbon in chemical evolution?

Accepted Answer

Carbon's ability to form four covalent bonds allows it to serve as a versatile building block for complex molecules.

Question 18

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

Accepted Answer

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

Question 19

Which of the following is a consequence of water's surface tension in biological systems?

Accepted Answer

Small insects can walk on water due to the cohesive forces between water molecules.

Water and Carbon: The Chemical Basis of Life – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard