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

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

Question 1

Which property of water is primarily responsible for the ability of some insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

A sodium atom (Na) has 11 protons and 11 electrons. When it loses one electron to form Na+, what happens to its charge and why?

Accepted Answer

It becomes positively charged because it has more protons than electrons.

Question 3

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

Accepted Answer

Hydrogen bonds in ice create a lattice that is less dense than liquid water.

Question 4

What is the main reason water is considered a 'universal solvent'?

Accepted Answer

Water's polarity allows it to dissolve many ionic and polar substances.

Question 5

Which of the following equations correctly represents the dissociation of water?

Accepted Answer

$$\mathrm{H_2O} \rightarrow \mathrm{H^+} + \mathrm{OH^-}$$

Question 6

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

Accepted Answer

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

Question 7

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms.

Question 8

Why does sweating help cool the human body?

Accepted Answer

Evaporation of sweat requires energy, which is taken from the body as heat.

Question 9

Which of the following is an example of an emergent property of water that is critical for life on Earth?

Accepted Answer

Water’s high heat of vaporization, which helps moderate Earth's climate.

Question 10

A plant is able to transport water from its roots to its leaves against gravity. Which property of water is most directly responsible for this phenomenon?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 11

Which of the following statements about acids and bases is correct?

Accepted Answer

An acid increases the concentration of $$\mathrm{H^+}$$ ions in a solution.

Question 12

If a solution changes from pH 6 to pH 4, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times.

Question 13

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

Accepted Answer

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

Question 14

Which of the following is a real-world consequence of water’s high specific heat?

Accepted Answer

Coastal regions experience milder climates compared to inland areas.

Question 15

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is the number of protons in the nucleus and determines the element.

Question 16

A buffer solution is added to a solution of strong acid. What is the expected effect on the pH of the solution?

Accepted Answer

The pH will remain relatively stable.

Question 17

Which of the following is a correct statement about isotopes?

Accepted Answer

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

Question 18

Which of the following best explains why water has a high surface tension?

Accepted Answer

Hydrogen bonds between water molecules create a strong cohesive force at the surface.

Question 19

A patient is suffering from acidosis (low blood pH). Which of the following would be an appropriate physiological response to restore normal pH?

Accepted Answer

Increase the concentration of bicarbonate ions ($$\mathrm{$$HCO_3$$^-}) to $$buffer excess $$\mathrm{H^+}.$$

Question 20

Which of the following best describes the process of capillary action in plants?

Accepted Answer

Water moves up the plant stem due to cohesion and adhesion of water molecules.

Water and Its Importance in Biology: Structure, Properties, and Biological Roles

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