Question 1

Which element is present in the greatest mass in a 75 kg human body, and what is its approximate mass?

Accepted Answer

Oxygen, 46 kg

Question 2

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

Accepted Answer

Hydrogen bonding between water molecules resists changes in temperature.

Question 3

A lake is able to resist changes in pH after acid rain due to its buffering capacity. Which chemical equation best represents a buffering reaction in this context?

Accepted Answer

$$\mathrm{H_2CO_3 \rightleftharpoons H^+ + $$HCO_3$$^-}$$

Question 4

Which property of water allows insects to walk on its surface?

Accepted Answer

Surface tension due to hydrogen bonding

Question 5

Which of the following statements about atomic orbitals is correct?

Accepted Answer

Each s orbital can hold 2 electrons, and each p orbital can hold 2 electrons.

Question 6

Methane ($$\mathrm{CH_4$}) $$has a tetrahedral shape. What is the main reason for this geometry?

Accepted Answer

The carbon atom undergoes sp$$^3$$ hybridization, creating four equivalent orbitals.

Question 7

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

Accepted Answer

Polar covalent bonds share electrons unequally due to differences in electronegativity, while nonpolar covalent bonds share electrons equally.

Question 8

A student adds salt (NaCl) to water and observes it dissolves. Which property of water explains this phenomenon?

Accepted Answer

Water's polarity allows it to dissolve ionic compounds

Question 9

Which of the following elements is present in the smallest amount by mass in a 75 kg human?

Accepted Answer

Iron

Question 10

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

Accepted Answer

Hydrogen bonding in ice keeps water molecules further apart, making it less dense.

Question 11

Which of the following is a real-world consequence of water's high heat of vaporization?

Accepted Answer

Sweating cools the human body as water evaporates from the skin.

Question 12

Which of the following best describes the role of hydrogen bonds in the properties of water?

Accepted Answer

They are responsible for water's cohesion, adhesion, and high surface tension.

Question 13

A solution has a pH of 3. Which of the following best describes this solution?

Accepted Answer

It is acidic and has a high concentration of $$\mathrm{H^+}$$ ions.

Question 14

Which of the following best explains why carbon is able to form such a wide variety of molecules essential for life?

Accepted Answer

Carbon can form up to four covalent bonds due to its four valence electrons.

Question 15

Which of the following is an example of a buffer system in the human body?

Accepted Answer

$$\mathrm{H_2CO_3 \rightleftharpoons H^+ + $$HCO_3$$^-}$$

Question 16

Which of the following best describes the relationship between pH and hydrogen ion concentration?

Accepted Answer

As pH decreases, $$[\mathrm{H^+}]$$ increases.

Question 17

Which of the following best explains why lakes with low buffering capacity are more vulnerable to acid rain?

Accepted Answer

They have fewer ions to neutralize added acids.

Question 18

Which of the following is a correct statement about the distribution of elements in the human body?

Accepted Answer

Oxygen, carbon, hydrogen, and nitrogen make up the majority of body mass.

Question 19

Which of the following best describes the process of hybridization in carbon atoms?

Accepted Answer

It results in the mixing of s and p orbitals to form four equivalent sp$$^3$$ orbitals.

Question 20

A molecule of water can form hydrogen bonds with other water molecules. Which atoms are directly involved in these hydrogen bonds?

Accepted Answer

Oxygen of one water molecule and hydrogen of another

Essential Elements and Chemical Properties in Biology

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