Chapter 20 - Acids, Bases, and pH

Question 1

What is a Bronsted-Lowry acid defined as?

Answer 1

A proton donor

Question 2

What is a Bronsted-Lowry base defined as?

Answer 2

A proton acceptor

Question 3

What is a conjugate acid-base pair?

Answer 3

Two species that can be interconverted by transfer of a proton.

Question 4

In the dissociation of HCl to H+ and Cl-, identify the conjugate acid and base.

Answer 4

HCl releases a proton so is therefore the conjugate acid.

Cl- accepts a proton so is therefore the conjugate base.

Question 5

When water is the base, what is formed?

Answer 5

H(3)O+

Hydronium ion

Question 6

What do the terms monobasic, dibasic and tribasic refer to?

Answer 6

The total number of hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction.

Question 7

How can redox reactions be simplified?

Answer 7

Remove the spectator ions

Question 8

What is the word equation for the reaction of an acid and a metal?

Answer 8

acid + metal -> salt + hydrogen

Question 9

What is the word equation for the reaction of an acid and a carbonate?

Answer 9

acid + carbonate -> salt + water + carbon dioxide

Question 10

What is the word equation for the reaction of an acid and a base?

Answer 10

acid + base -> salt + water

Question 11

What is the word equation for the reaction of an acid and an alkali?

Answer 11

acid + alkali -> salt + water

Question 12

What is the relationship between pH and concentration of H+?

Answer 12

Low value [H+] = high pH

High value [H+] = low pH

Question 13

What is the equation for working out pH from [H+]?

Answer 13

pH = -log[H+] (base 10)

Question 14

How is the pH calculated for a strong acid?

Answer 14

Assume it fully dissociates

Therefore [H+] = [HA]

Question 15

How is the new pH calculated for a strong acid on dilution?

Answer 15

Work out change in concentration of HA and therefore [H+]

Then put back into pH = -log[H+]

Question 16

How is the pH calculated for a weak acid?

Answer 16

Ka = [H+][A-]/[HA]
Ka[HA] = [H+][A-]
[H+] = [A-]
[H+]^2 = Ka[HA]
[H+] = sqrt(Ka[HA])

Question 17

What is Kw?

Answer 17

The ionic product of water

Question 18

What is the value of pKw?

Answer 18

14.00

Question 19

How can pH of strong bases be found when given the concentration of OH-?

Answer 19

pKw = pH + pOH

Question 20

How can pH of weak bases be found when given the concentration of OH-?

Answer 20

Similar method to weak acids, with the additional step of pKw = pH +pOH

Question 21

what is the pOH formula

Answer 21

pOH= -log[OH(aq)]

Question 22

What is the formula of [OH-(aq)]

Answer 22

10^-pOH

Question 23

pKa value formula

Answer 23

pKa = -log ka

Question 24

What is the unlog of pKa

Answer 24

Ka = 10^-pKa

Question 25

limitations of using approximations to Ka related calculations for ‘stronger’ weak acids

Answer 25

[HA]equilibrium ~ [HA]undissociated may no longer be valid.

The approximation that the concentration of acid is much greater than the H+ concentration at equilibrium is not valid