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

$$[H^+] = 1 \times 10$$^{-4}$$ \ \mathrm{M}$$

Question 1

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond to create sodium chloride (NaCl)?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 2

Which element makes up the largest percentage of the human body by weight, and what is its approximate percentage?

Accepted Answer

Oxygen, 65.0%

Question 3

A radioactive isotope of carbon, $$^{14}C$$, is used in radiocarbon dating. What makes $$^{14}C$$ different from the most common carbon isotope, $$^{12}C$$?

Accepted Answer

$$^{14}C$$ has more neutrons than $$^{12}C.$$

Question 4

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms.

Question 5

Water is often called the 'universal solvent.' Which property of water is primarily responsible for this characteristic?

Accepted Answer

Its ability to form hydrogen bonds with many substances.

Question 6

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

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ \ \mathrm{M}$$

Question 7

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

Accepted Answer

Acids release $$H^+$$ ions, while bases either absorb $$H^+ or $$release $$OH^-$$ ions.

Question 8

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

Accepted Answer

Hydrogen bonds in ice create a lattice structure that is less dense than liquid water.

Question 9

A buffer solution is important in biological systems because it:

Accepted Answer

Maintains a relatively constant pH by absorbing excess $$H^+ or$$ $$OH^-$$ ions.

Question 10

Which of the following is a trace element in the human body, making up less than 0.01% of body weight?

Accepted Answer

Iron (Fe)

Question 11

If an atom has 11 protons, 12 neutrons, and 10 electrons, what is its net charge and what is it called?

Accepted Answer

Net charge: +1, called a cation

Question 12

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

Accepted Answer

A molecule is any group of atoms bonded together, while a compound is a molecule made of different elements.

Question 13

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

Accepted Answer

Hydrogen bonds between water molecules require more energy to break.

Question 14

A patient is experiencing acidosis, meaning their blood pH is below 7.4. Which of the following would help restore their blood pH to normal?

Accepted Answer

Adding a buffer that absorbs $$H^+$$ ions.

Question 15

Which of the following is an example of a polar covalent bond?

Accepted Answer

The bond between hydrogen and oxygen in a water molecule.

Question 16

Which of the following best describes van der Waals interactions?

Accepted Answer

Weak attractions between molecules due to temporary dipoles.

Question 17

If a chemical reaction is at equilibrium, which of the following is true?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction.

Question 18

Which of the following best explains why living organisms require trace elements such as zinc (Zn) and copper (Cu)?

Accepted Answer

They are essential cofactors for many enzymes and biological processes.

Question 19

Which of the following statements about electron shells is correct?

Accepted Answer

Atoms are most stable when their valence shell is full.

Question 20

A molecule of ammonia ($$NH_3) $$acts as a base in water. Which of the following best describes what happens?

Accepted Answer

$$NH_3$$ absorbs $$H^+$$ ions from the solution.

The Chemical Basis of Life: Atoms, Elements, and Chemical Bonds

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