Question 1

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

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 2

Given an element X with atomic number 75 and mass number 78, how many neutrons does it have?

Accepted Answer

$$78 - 75 = 3$$ neutrons

Question 3

In an ammonia ($$NH_3) $$molecule, what type of bond is formed between nitrogen and hydrogen atoms?

Accepted Answer

Polar covalent bond

Question 4

Which of the following best describes a hydrogen bond?

Accepted Answer

A temporary bond between polar molecules, often involving hydrogen and either oxygen or nitrogen

Question 5

Why does water have a high surface tension?

Accepted Answer

Because of hydrogen bonding between water molecules

Question 6

Which property allows water to dissolve many substances, making it the 'universal solvent'?

Accepted Answer

Its polarity, which allows it to interact with and dissolve polar and ionic substances

Question 7

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

Accepted Answer

$$10^{2} = 100$ times more H$$^+$$ ions

Question 8

What happens to the pH of a solution when hydrochloric acid ($$HCl) is $$added?

Accepted Answer

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

Question 9

Which of the following best describes an amphipathic molecule?

Accepted Answer

A molecule with both hydrophilic (polar) and hydrophobic (nonpolar) regions

Question 10

If sodium hydroxide ($$NaOH) is $$added to water, what is the effect on the $$H^+$$ and $$OH^-$$ concentrations?

Accepted Answer

$$OH^-$$ increases and $$H^+$$ decreases, making the solution more basic

Question 11

Which of the following statements about buffers is correct?

Accepted Answer

Buffers minimize changes in pH by binding or releasing $$H^+$$ ions

Question 12

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

Accepted Answer

The polarity of water, which causes hydrophobic regions to avoid contact with water

Question 13

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

Accepted Answer

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

Question 14

Which of the following is an example of a hydrophobic substance?

Accepted Answer

A long-chain fatty acid

Question 15

What is the pH of pure water at equilibrium at 25°C?

Accepted Answer

$$pH = 7$$

Question 16

Which step in the scientific method comes immediately after forming a hypothesis?

Accepted Answer

Design an experiment

Question 17

A researcher observes that seeds germinate faster at 35°C than at 25°C. Which part of the scientific method does this represent?

Accepted Answer

Making an observation

Question 18

Which of the following best describes a solution?

Accepted Answer

A homogenous mixture of a solute dissolved in a solvent

Question 19

If the concentration of $$H^+ in a $$solution is $$1 	imes 10$$^{-4}$$ M, what is the pH of the solution?

Accepted Answer

$$pH = 4$$

Question 20

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

Accepted Answer

Acids increase the concentration of $$H^+$$ ions in solution, while bases decrease it

Introduction to General Biology: Elements of Life, Chemical Bonds, Water, and the Scientific Method

Guida di studio - Domande di pratica

Study guide - Flashcard