wk 3

Question 1

What happens when water ionizes?

Answer 1

Water splits into hydrogen ions (H⁺) and hydroxide ions (OH⁻).

Question 2

What does a hydrogen ion consist of?

Answer 2

A single proton.

Question 3

What is hydronium?

Answer 3

A water molecule (H₂O) that has gained an extra hydrogen ion, forming H₃O⁺.

Question 4

What is an acid?

Answer 4

A substance that donates hydrogen ions (H⁺) in solution.

Example: Hydrochloric acid (HCl).

Question 5

What is a base?

Answer 5

A substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻).

Examples: Sodium hydroxide (NaOH) and ammonia (NH₃).

Question 6

What scale is used to express acidity?

Answer 6

The pH scale.

Question 7

What does pH measure?

Answer 7

The concentration of hydrogen ions (H⁺) in a solution.

Question 8

Describe the pH scale.

Answer 8

Ranges from 0–14; 7 is neutral, below 7 is acidic, above 7 is basic.

Question 9

Describe the concentration of OH⁻ and H⁺ ions:

Answer 9

Basic: More OH⁻ than H⁺; Neutral: Equal amounts of H⁺ and OH⁻; Acidic: More H⁺ than OH⁻.

Question 10

What is acid-base neutralization?

Answer 10

When an acid and a base react to form water and a salt.

Question 11

What determines if a solution is acidic or basic?

Answer 11

The relative concentrations of H⁺ and OH⁻ ions.

Question 12

pH is a logarithmic scale. What does this mean?

Answer 12

Each pH unit represents a 10x change in H⁺ concentration.

Question 13

What is the normal pH range of human blood?

Answer 13

7.35–7.45.

Question 14

How is it maintained?

Answer 14

By buffer systems.

Question 15

What is a buffer?

Answer 15

A substance that minimizes changes in pH by accepting or donating H⁺ ions.

Question 16

Which buffer system maintains pH homeostasis in humans?

Answer 16

The bicarbonate buffer system.

Chemical Equation: CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻.

Question 17

Where does the carbon dioxide in the bicarbonate buffer system come from?

Answer 17

Cellular respiration.

Question 18

In the human pH buffering system, what is the conjugate pair?

Answer 18

H₂CO₃ (carbonic acid) and HCO₃⁻ (bicarbonate ion).

Question 19

What does the two-way arrow mean?

Answer 19

The reaction is reversible.

Question 20

What happens when blood becomes too acidic (pH drops)?

Answer 20

Bicarbonate binds H⁺ ions to neutralize the acid.

Question 21

What happens when blood becomes too basic (pH rises)?

Answer 21

Carbonic acid releases H⁺ ions to lower the pH.

Question 22

When do buffers donate vs. accept protons?

Answer 22

Donate when pH rises (too basic); accept when pH drops (too acidic).

Question 23

Water is a polar molecule. What does this mean?

Answer 23

It has a partial positive charge on hydrogen atoms and a partial negative charge on oxygen.

Question 24

What is a hydrogen bond?

Answer 24

A weak bond between a hydrogen atom and an electronegative atom like oxygen or nitrogen.

Question 25

What properties of water result from its polarity?

Answer 25

Cohesion, adhesion, solvency, thermal stability.

Question 26

What is solvency?

Answer 26

Water’s ability to dissolve other substances, especially polar molecules and ions.

Question 27

Difference between hydrophilic and hydrophobic substances?

Answer 27

Hydrophilic substances dissolve in water; hydrophobic substances do not.

Question 28

What type of bond does water easily overpower?

Answer 28

Ionic bonds.

Question 29

How does water form a hydration sphere around ions?

Answer 29

Water molecules surround ions with their oppositely charged ends facing the ion.

Question 30

Difference between adhesion and cohesion?

Answer 30

Adhesion: water sticks to other surfaces. Cohesion: water sticks to itself. Both are due to hydrogen bonding.

Question 31

What is chemical reactivity?

Answer 31

Water participates in chemical reactions, such as hydrolysis and dehydration synthesis.

Question 32

Why does water have high thermal stability?

Answer 32

It can absorb a lot of heat without a large temperature change, due to hydrogen bonding.

Question 33

What is a solution?

Answer 33

A homogenous mixture of solute and solvent.

Question 34

What is a colloid?

Answer 34

A mixture where particles are larger than in a solution but do not settle out.

Question 35

What is a suspension?

Answer 35

A mixture where particles are large enough to settle out over time.

Question 36

What is concentration?

Answer 36

The amount of solute in a solution. ## Footnote Measured by: molarity, % solutions, or weight/volume.

Question 37

What is a mole?

Answer 37

6.022 × 10²³ particles (Avogadro’s number).

Question 38

What is molar mass?

Answer 38

The mass of one mole of a substance, measured in grams/mole (g/mol).

Question 39

How do chemists use molar mass?

Answer 39

To calculate how much of a substance to use in reactions.

Question 40

What is molarity?

Answer 40

Moles of solute per liter of solution. ## Footnote Formula: M = moles/L.

Question 41

What is a chemical reaction?

Answer 41

A process where substances change into different substances. ## Footnote Evidence: Color change, gas production, temperature change, precipitate formation.

Question 42

What do chemists use to symbolize a chemical reaction?

Answer 42

A chemical equation.

Question 43

What is a reactant?

Answer 43

Substance present before the reaction.

Question 44

What is a product?

Answer 44

Substance formed after the reaction.

Question 45

What does the arrow mean?

Answer 45

Yields or produces.

Question 46

What is a coefficient?

Answer 46

A number in front of a chemical formula, showing quantity. ## Footnote Example: 2H₂O.

Question 47

What is a subscript?

Answer 47

A small number showing how many atoms are in a molecule. ## Footnote Example: H₂O (the “2”).

Question 48

What is a phase symbol?

Answer 48

Symbol showing the state of matter: • (s) = solid • (l) = liquid • (g) = gas • (aq) = aqueous (dissolved in water).

Question 49

Name the three classes of chemical reactions.

Answer 49

Synthesis, decomposition, exchange.

Question 50

Describe a synthesis reaction.

Answer 50

Two or more substances combine to form a new substance (A + B → AB).

Question 51

Describe a decomposition reaction.

Answer 51

One substance breaks apart into two or more simpler substances (AB → A + B).

Question 52

Describe an exchange reaction.

Answer 52

Parts of molecules swap places (AB + CD → AD + CB).

Question 53

What is a reversible reaction?

Answer 53

A reaction that can go both forward and backward. ## Footnote Symbol: ⇌.

Question 54

What is collision theory?

Answer 54

Particles must collide with enough energy and the correct orientation for a reaction to occur.

Question 55

What factors influence reaction rate?

Answer 55

Temperature, concentration, surface area, catalysts.

Question 56

Describe how a catalyst works.

Answer 56

Lowers the activation energy needed for a reaction, making it faster.

Question 57

Why must chemical equations be balanced?

Answer 57

To obey the law of conservation of mass — matter cannot be created or destroyed.

Question 58

How can you tell if an equation is balanced?

Answer 58

The number of each type of atom is the same on both sides of the equation.

Question 59

Multiple choice test-taking strategy: Give one useful or surprising one and why.

Answer 59

Example: Eliminate obviously wrong answers first — this increases chances even if you have to guess!