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

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

Question 1

Which of the following best explains why sodium chloride (NaCl) has properties very different from both sodium metal and chlorine gas?

Accepted Answer

Chemical bonding creates emergent properties that are not present in the individual elements.

Question 2

A scientist discovers a new element with 17 protons, 18 neutrons, and 17 electrons. What is the atomic mass of this element?

Accepted Answer

$$35$$

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 4

Why is water considered an excellent solvent for many biological molecules?

Accepted Answer

Water's polarity allows it to form hydrogen bonds with ions and polar molecules.

Question 5

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating hydrogen ions.

Question 6

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

Accepted Answer

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

Question 7

Which of the following is a trace element required for normal thyroid function in vertebrates?

Accepted Answer

Iodine

Question 8

What must an electron do to move from a lower energy shell to a higher energy shell?

Accepted Answer

Absorb energy

Question 9

Which of the following best describes a state of dynamic equilibrium in a chemical reaction?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 10

Which property of water is most directly responsible for the ability of insects to walk on water surfaces?

Accepted Answer

Cohesion due to hydrogen bonding

Question 11

A buffer solution contains carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). What happens when a small amount of acid is added to this solution?

Accepted Answer

The bicarbonate ions neutralize the added hydrogen ions, minimizing pH change.

Question 12

Which of the following is the primary cause of increased atmospheric carbon dioxide leading to ocean acidification?

Accepted Answer

Human activities such as fossil-fuel burning and cement production.

Question 13

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

Accepted Answer

A compound consists of two or more elements in a fixed ratio, while a mixture is a physical combination in variable proportions.

Question 14

Which four elements make up approximately 96.3% of human body mass?

Accepted Answer

Carbon, Hydrogen, Oxygen, Nitrogen

Question 15

What does the calibration mark on the neck of a volumetric flask indicate when preparing a chemical solution?

Accepted Answer

The final volume of the prepared solution.

Question 16

Which of the following best explains why carbon dioxide ($$CO_2) is a $$nonpolar molecule, even though it contains polar bonds?

Accepted Answer

The molecule is linear, so the dipoles cancel each other out.

Question 17

Which of the following is a real-world application of radioactive isotopes in medicine?

Accepted Answer

Using isotopes to trace metabolic pathways in PET scans.

Question 18

If a solution changes from pH 7 to pH 5, how does the hydrogen ion concentration change?

Accepted Answer

It increases by a factor of 100.

Question 19

Which of the following best describes the relationship between acid strength and acid concentration?

Accepted Answer

Acid strength refers to how completely an acid ionizes, while acid concentration refers to the amount of acid per unit volume.

The Chemical Context of Life: Foundations for General Biology

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