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

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

Question 1

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

Accepted Answer

Hydrogen bonds in ice form a more ordered structure, creating open spaces and making ice less dense than liquid water.

Question 2

A patient is diagnosed with goiter due to a deficiency of which essential element?

Accepted Answer

Iodine (I)

Question 3

Which statement about compounds is correct?

Accepted Answer

Compounds have emergent properties different from those of their elements.

Question 4

A sodium atom has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 5

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

Accepted Answer

Dating fossils using carbon-14 decay

Question 6

What determines the chemical behavior of an atom?

Accepted Answer

The distribution of electrons in electron shells, especially the valence shell

Question 7

Which type of chemical bond involves the sharing of a pair of valence electrons between two atoms?

Accepted Answer

Covalent bond

Question 8

In a water molecule ($$H_2O$$), the oxygen atom is more electronegative than the hydrogen atoms. What type of covalent bond is formed between oxygen and hydrogen?

Accepted Answer

Polar covalent bond

Question 9

Which of the following best describes the process of evaporative cooling?

Accepted Answer

As water evaporates, the remaining surface cools because the molecules with the highest kinetic energy leave first.

Question 10

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

Accepted Answer

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

Question 11

Which property of water allows plants to transport water from roots to leaves against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 12

Which of the following is a consequence of ocean acidification caused by increased $$CO_2$$ absorption?

Accepted Answer

Decrease in carbonate ion concentration, threatening organisms that build shells and coral

Question 13

Which of the following best describes a buffer in biological systems?

Accepted Answer

A buffer is a substance that minimizes changes in $$[H^+]$$ and $$[OH^-]$$ concentrations.

Question 14

Which of the following interactions is responsible for the temporary binding of biological molecules with complementary shapes?

Accepted Answer

Weak chemical interactions such as hydrogen bonds and van der Waals forces

Question 15

A molecule with many nonpolar covalent bonds is likely to be:

Accepted Answer

Hydrophobic

Question 16

Which equation correctly represents the relationship between hydrogen ion and hydroxide ion concentrations in any aqueous solution at 25°C?

Accepted Answer

$$[H^+][OH^-] = 10$$^{-14}$$

Question 17

Which of the following best describes the role of van der Waals interactions in biological systems?

Accepted Answer

They are weak interactions that, when numerous, can provide significant adhesion, such as a gecko’s foot sticking to a wall.

Question 18

Which of the following is true about the specific heat of water?

Accepted Answer

It is high due to hydrogen bonding, allowing water to resist temperature changes.

Question 19

Which of the following is a correct statement about acids and bases?

Accepted Answer

Bases increase the $$[OH^-]$$ concentration in water.

Question 20

A solution is prepared by dissolving 1 mole of NaCl in enough water to make 1 liter of solution. What is the molarity ($$M) of $$NaCl in the solution?

Accepted Answer

$$M = 1 M$$

Chapter 2: The Chemical Context of Life – Study Notes

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