Question 1

Which of the following best describes a compound?

Accepted Answer

A substance formed when two or more elements are chemically combined in fixed ratios.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Carbon, Oxygen, Hydrogen, Nitrogen

Question 3

An atom of sodium (Na) has an atomic number of 11 and an atomic mass of about 23 daltons. How many neutrons does a typical sodium atom have?

Accepted Answer

$23 - 11 = 12$ neutrons

Question 4

Which statement about isotopes is correct?

Accepted Answer

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

Question 5

Which type of chemical bond is the strongest in biological molecules?

Accepted Answer

Covalent bond

Question 6

Water is an excellent solvent for many biological molecules because:

Accepted Answer

It forms hydrogen bonds due to its polarity.

Question 7

Which of the following best explains why table salt (NaCl) dissolves in water?

Accepted Answer

Water's polarity allows it to surround and separate Na+ and Cl- ions.

Question 8

A buffer helps maintain pH in biological systems by:

Accepted Answer

Donating or accepting H+ ions to resist changes in pH.

Question 9

Which of the following is a trace element essential for thyroid hormone production, and its deficiency can lead to goiter?

Accepted Answer

Iodine (I)

Question 10

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak bond formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Question 11

Which of the following equations correctly represents the relationship between atomic number ($Z$), mass number ($A$), number of protons ($p$), and number of neutrons ($n$)?

Accepted Answer

$A = Z + n$

Question 12

Which property of water is most important for the cohesion of water molecules in plant transport?

Accepted Answer

Hydrogen bonding

Question 13

A solution has a high concentration of H+ ions. Which of the following best describes this solution?

Accepted Answer

It is an acid.

Question 14

Which of the following statements about electron configuration is correct?

Accepted Answer

Electrons fill the innermost shells first, and valence electrons are found in the outermost shell.

Question 15

Which of the following is a biological example of an ionic bond?

Accepted Answer

NaCl (table salt)

Question 16

Which of the following best explains the importance of molecular shape in biological systems?

Accepted Answer

Molecular shape is critical for interactions such as enzyme-substrate binding and hormone-receptor recognition.

Question 17

Which of the following is true about buffers in the human body?

Accepted Answer

The carbonic acid-bicarbonate buffer system helps maintain stable blood pH.

Question 18

Which of the following is a correct statement about major and trace elements?

Accepted Answer

Major elements make up most of the organism's mass, while trace elements are needed in minute quantities.

Question 19

Which of the following is a correct application of radioactive isotopes in medicine?

Accepted Answer

They are used as tracers in biological research and diagnostic imaging.

Elements, Compounds, and Chemical Properties: Foundations of General Biology

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