Q: A solution has a hydrogen ion concentration of $1 \times 10^{-4}$ M. What is its pH?

$pH = -\log_{10}(1 \times 10^{-4}) = 4$

Q: How many grams of NaCl are needed to make 500 mL of a 0.2 M solution? (Molecular weight of NaCl = 58 g/mol)

$0.2 \times 0.5 \times 58 = 5.8$ g

Question 1

Which of the following best explains why covalent bonds are critical to biological systems?

Accepted Answer

They allow atoms to share electrons, creating stable molecules essential for life.

Question 2

A solution has a hydrogen ion concentration of $1 	imes 10^{-4}$ M. What is its pH?

Accepted Answer

$pH = -\log_{10}(1 	imes 10^{-4}) = 4$

Question 3

Which property of water is most responsible for its ability to dissolve ionic substances like NaCl?

Accepted Answer

Water's dipolar nature and ability to form spheres of hydration

Question 4

Which of the following bonds is strongest in water?

Accepted Answer

Covalent bond

Question 5

A buffer solution contains acetic acid ($CH_3COOH$) and its conjugate base ($CH_3COO^-$). What is the main function of this buffer in a biological system?

Accepted Answer

To resist changes in pH when small amounts of acid or base are added

Question 6

Which functional group is classified as a weak acid and is commonly found in amino acids?

Accepted Answer

Carboxyl group ($-COOH$)

Question 7

How many grams of NaCl are needed to make 500 mL of a 0.2 M solution? (Molecular weight of NaCl = 58 g/mol)

Accepted Answer

$0.2 	imes 0.5 	imes 58 = 5.8$ g

Question 8

Which of the following best describes a hydrophobic interaction?

Accepted Answer

Repulsion of nonpolar molecules from water, causing them to cluster together

Question 9

Which element makes up the largest percentage of human body weight?

Accepted Answer

Oxygen

Question 10

Which of the following is a condensation reaction?

Accepted Answer

Joining two monomers to form a polymer and releasing water

Question 11

Which of the following statements about amino acids is correct?

Accepted Answer

All amino acids have a carboxyl group, an amino group, and a unique R-group.

Question 12

Which of the following is a property of water that is essential for life?

Accepted Answer

Water has a high specific heat, allowing it to moderate temperature changes.

Question 13

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA is mostly double-stranded, while RNA is mostly single-stranded.

Question 14

Which of the following is a structural polysaccharide found in plant cell walls?

Accepted Answer

Cellulose

Question 15

What is the pH of a 0.01 M NaOH solution? (Assume complete dissociation)

Accepted Answer

$pH = 12$

Question 16

Which of the following is true about van der Waals attractions?

Accepted Answer

They are weak interactions caused by transient electrical charges and are significant when many are present.

Question 17

Which of the following is a correct formula for calculating pH?

Accepted Answer

$pH = -\log_{10}[H^+]$

Question 18

Which of the following best describes the role of cholesterol in cell membranes?

Accepted Answer

It increases membrane fluidity and is a precursor for steroid hormones.

Question 19

Which of the following is a correct description of a peptide bond?

Accepted Answer

A peptide bond is an amide linkage formed by a condensation reaction between amino acids.

Question 20

Which of the following statements about macromolecules is correct?

Accepted Answer

Sequence of monomers determines the structure and function of macromolecules.

Chemical Components of Cells: Structure, Function, and Biological Importance

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