Question 1

Which four elements make up approximately 96% of the mass of living organisms?

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 2

An atom has a mass number of 78 and an atomic number of 75. How many neutrons does it have?

Accepted Answer

3

Question 3

In ammonia ($$NH_3$$), the electronegativity difference between nitrogen and hydrogen is $$3.04 - 2.20 = 0.84. $$What type of bond is formed between nitrogen and hydrogen?

Accepted Answer

Polar covalent bond

Question 4

Which step in the scientific method involves making a testable statement that can be supported or contradicted by experimental data?

Accepted Answer

Forming a hypothesis

Question 5

Water is described as a 'universal solvent.' Which property of water allows it to dissolve many substances?

Accepted Answer

Its polarity

Question 6

What is the main reason water molecules form hydrogen bonds with each other?

Accepted Answer

Water molecules are polar, with partial positive and negative charges

Question 7

Which of the following best describes the difference between cohesion and adhesion in water?

Accepted Answer

Cohesion is water molecules sticking to each other; adhesion is water molecules sticking to other surfaces

Question 8

A solution has a pH of 5. How many times more $$H^+$$ ions does it have compared to a solution with a pH of 7?

Accepted Answer

$$100$$ times more

Question 9

Which of the following equations correctly expresses the relationship between pH and hydrogen ion concentration?

Accepted Answer

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

Question 10

If you add hydrochloric acid ($$HCl) to $$pure water, what happens to the concentration of $$H^+$$ ions and the pH?

Accepted Answer

The concentration of $$H^+$$ ions increases and the pH decreases

Question 11

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

Accepted Answer

A substance that minimizes changes in pH by binding excess $$H^+ or$$ $$OH^-$$ ions

Question 12

Which type of molecule is most likely to be hydrophobic?

Accepted Answer

A nonpolar molecule

Question 13

Amphipathic molecules have both hydrophilic and hydrophobic regions. Which biological structure is primarily formed by amphipathic molecules?

Accepted Answer

Cell membranes

Question 14

Which of the following is true about the dissociation of water?

Accepted Answer

It produces equal concentrations of $$H^+$$ and $$OH^-$$ ions in pure water

Question 15

A protein folds so that its hydrophobic amino acids are buried inside and hydrophilic amino acids are exposed to water. What property of water drives this folding?

Accepted Answer

Water's polarity and ability to form hydrogen bonds

Question 16

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

Accepted Answer

Hydrogen bonding between water molecules

Question 17

If sodium hydroxide ($$NaOH) is $$added to water, what happens to the $$OH^-$$ concentration and the pH?

Accepted Answer

$$OH^-$$ concentration increases and pH increases

Question 18

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

Accepted Answer

Acids increase $$H^+$$ concentration; bases decrease $$H^+$$ concentration

Question 19

Which of the following molecules would most likely dissolve in water?

Accepted Answer

A molecule with polar covalent bonds

Question 20

A buffer system in blood uses bicarbonate ($$HCO_3$$^-$$) to maintain pH. If excess H$$^+$$ ions are added, what happens?

Accepted Answer

Bicarbonate binds $$H^+$$ ions, minimizing pH change

Fundamental Chemistry and Water in Biology: Study Notes for BIOL 141

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