Acids And Bases

Question 1

Define a Brønsted-Lowry acid.

Answer 1

A Brønsted-Lowry acid is a proton donor.

Question 2

Give an example of a Brønsted-Lowry acid.

Answer 2

Ammonium ions (NH4+).

Question 3

Define a Brønsted-Lowry base.

Answer 3

A Brønsted-Lowry base is a proton acceptor.

Question 4

Give an example of a Brønsted-Lowry base.

Answer 4

Hydroxide ions (OH-).

Question 5

Describe the relationship between acid strength and dissociation.

Answer 5

A strong acid completely dissociates to ions in solution, while a weak acid only slightly dissociates.

Question 6

What pH range is associated with strong acids?

Answer 6

Strong acids have a pH range of 0-1.

Question 7

What pH range is associated with weak acids?

Answer 7

Weak acids have a pH range of 3-5.

Question 8

Explain the pH range for strong bases.

Answer 8

Strong bases have a pH range of 12-14.

Question 9

Explain the pH range for weak bases.

Answer 9

Weak bases have a pH range of 9-11.

Question 10

How can substances be classified as acids or bases?

Answer 10

Substances can be classified as acids or bases based on their interaction with protons.

Question 11

What does acid strength not refer to?

Answer 11

Acid strength does not refer to the concentration of a solution.

Question 12

Define pH.

Answer 12

pH is a measure of acidity and alkalinity, represented on a logarithmic scale from 0 to 14, indicating the concentration of H+ ions in a solution.

Question 13

Describe the significance of a pH of 0.

Answer 13

A pH of 0 indicates an acidic solution with a high concentration of H+ ions.

Question 14

Describe the significance of a pH of 14.

Answer 14

A pH of 14 indicates a basic solution with a low concentration of H+ ions.

Question 15

How can the concentration of H+ ions be determined?

Answer 15

The concentration of H+ ions can be determined if the pH of the solution is known.

Question 16

Explain the relationship between strong acids and H+ ion concentration.

Answer 16

The concentration of H+ ions in a solution is equivalent to the concentration of a strong acid, as strong acids completely dissociate into ions.

Question 17

What is the ionic product of water (Kw) at 25°C?

Answer 17

At 25°C, the ionic product of water (Kw) has a constant value of 1 x 10^-14.

Question 18

How does temperature affect the ionic product of water?

Answer 18

As temperature changes, the value of the ionic product of water (Kw) also changes.

Question 19

Describe the nature of the forward reaction in the equilibrium of water.

Answer 19

The forward reaction in the equilibrium of water is endothermic and is favored when the temperature of the water is increased.

Question 20

What happens to H+ ion production as the temperature of water increases?

Answer 20

As the temperature of water increases, more H+ ions are produced, making the water more acidic.

Question 21

Describe the dissociation of weak acids and bases in solution.

Answer 21

Weak acids and bases only slightly dissociate in solution, forming an equilibrium mixture.

Question 22

Define the equilibrium dissociation constant for weak acids.

Answer 22

The equilibrium dissociation constant for weak acids is denoted as Ka.

Question 23

How can pKa be used in relation to weak acids and bases?

Answer 23

pKa can be used to find the concentration of hydrogen ions

Question 24

Explain the method to find pH when HA is in excess.

Answer 24

When HA is in excess, use the concentrations of [HA] and [A - ] along with Ka to find [H + ], then calculate pH.

Question 25

What is the approach when A - is in excess?

Answer 25

When A - is in excess, use the ion product of water, Kw, to find [H + ], then calculate pH.

Question 26

How is pKa related to pH when HA equals A - ?

Answer 26

When HA equals A - , pKa is equal to pH, so you can find pKa directly.

Question 27

Describe a pH titration curve.

Answer 27

A pH titration curve shows how the pH of a solution changes during an acid-base reaction.

Question 28

What is the significance of the neutralisation point in a titration curve?

Answer 28

The neutralisation point is identified as a large vertical section in the titration curve, indicating the equivalence point of the acid-base reaction.

Question 29

Describe the process of investigating the pH of an acid-base reaction.

Answer 29

Alkali is slowly added to an acid while measuring the pH with a pH probe, or vice versa. Smaller added volumes yield a more accurate pH curve.

Question 30

Define the neutralization point for a strong acid and strong base reaction.

Answer 30

The neutralization point for a strong acid and strong base reaction occurs around pH 7.

Question 31

How does the neutralization point differ between strong acids and weak bases?

Answer 31

For a strong acid and weak base reaction, the neutralization point is less than pH 7, indicating a more acidic solution.

Question 32

What is the expected pH when a weak acid reacts with a strong base?

Answer 32

The expected pH when a weak acid reacts with a strong base is greater than pH 7, indicating a more basic solution.

Question 33

Explain the neutralization point for weak acid and weak base combinations.

Answer 33

The neutralization point for weak acid and weak base combinations is normally around pH 7, but it can be hard to determine accurately.

Question 34

How does the volume of alkali added affect the accuracy of the pH curve?

Answer 34

The smaller the added volumes of alkali, the more accurate the pH curve produced during the investigation.

Question 35

Describe the role of specific indicators in chemical reactions.

Answer 35

Specific indicators are used for specific reactions as they indicate a pH change within a certain range.

Question 36

Define methyl orange and its use in titrations.

Answer 36

Methyl orange is an indicator used for reactions with a more acidic neutralisation point, appearing orange in acids and turning yellow at the neutralisation point.

Question 37

Explain the color change of phenolphthalein in different pH environments.

Answer 37

Phenolphthalein is pink in alkalis and turns colourless at the neutralisation point, making it suitable for reactions with a more basic neutralisation point.

Question 38

How does the choice of indicator affect titration results?

Answer 38

The correct indicator must be selected based on the chemicals used in a titration to accurately reflect the pH change.

Question 39

What components make up an acidic buffer solution?

Answer 39

An acidic buffer solution contains a weak acid and the salt of that weak acid.

Question 40

Identify the components of a basic buffer solution.

Answer 40

A basic buffer solution consists of a weak base and the salt of that weak base.

Question 41

Describe the function of a buffer solution when an acid is added.

Answer 41

When an acid is added to a buffer solution, it resists a change in pH by reacting with the buffer components, such as ethanoate ions, to form the weak acid.

Question 42

How does a buffer solution maintain pH stability?

Answer 42

A buffer solution maintains pH stability by neutralizing small amounts of added acid or base, preventing significant changes in pH.

Question 43

Define a buffer solution in terms of pH changes.

Answer 43

A buffer solution is defined as a solution that can resist changes in pH when small volumes of acid or base are added.

Question 44

Describe the process of calculating pH for an acid and base buffer system.

Answer 44

Find the number of moles of each species, calculate their concentration at equilibrium using the total volume, and use Ka to find [H+] and therefore pH.

Question 45

How does adding small volumes of acid affect the pH of a buffer solution?

Answer 45

Adding small amounts of acid (H+) increases the concentration of the acid in the buffer solution, making the overall solution slightly more acidic.

Question 46

What happens to the pH of a buffer solution when small amounts of base are added?

Answer 46

Adding small amounts of base (OH-) decreases the concentration of acid in the buffer solution, making the overall solution slightly more basic.

Question 47

Define the role of buffer solutions in biological systems.

Answer 47

Buffer solutions help maintain a specific pH, which is crucial for the proper functioning of enzymes and reactions in living organisms.

Question 48

Explain the significance of buffer solutions in nature.

Answer 48

Buffer solutions are important for regulating systems in nature, ensuring that biological processes can occur within the required pH range.

Question 49

How do you calculate pH for an acid and salt buffer system?

Answer 49

Find the moles of the salt and use Ka to determine the pH.

Question 50

What is the typical change in pH when small volumes of acid or base are added to a buffer solution?

Answer 50

The pH of a buffer solution typically changes by about 0.1 or 0.01 units when small volumes of acid or base are added.