Acids, Bases and pH

Question 1

What is an alkali

Answer 1

a soluble base

Question 2

What is a bronsted-lowry acid

Answer 2

a proton donor

Question 3

What is a bronsted-lowry base

Answer 3

a proton acceptor

Question 4

What is a conjugate acid base pair

Answer 4

contains 2 species that can be interconverted by transfer of a proton

Question 5

What is a monobasic acid

Answer 5

there is 1 hydrogen ion in the acid that can be replaced per molecule in an acid-base reaction

Question 6

What is a dibasic acid

Answer 6

there are 2 hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction

Question 7

What is a tribasic acid

Answer 7

there are 3 hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction

Question 8

What is pH

Answer 8

-log[H+(aq)]

Question 9

How to work out H+ concentration from pH

Answer 9

10^-pH

Question 10

A change of 1 pH number is equal to how many times difference

Answer 10

x10

Question 11

What is a strong acid

Answer 11

completely dissociates in aqueous solution

Question 12

What is a weak acid

Answer 12

partially dissociates in aqueous solution

Question 13

What is Ka

Answer 13

the acid dissociation constant used for acid base equilibria

Question 14

What is the Ka formula

Answer 14

[H+][A-] /[HA]

Question 15

What can cause Ka to change

Answer 15

Temperature

Question 16

What does a large Ka mean

Answer 16

Further equilibrium is to the right. The greater the disassociation/strength of acid

Question 17

How do you convert Ka to pka

Answer 17

-log(ka)

Question 18

How do you convert pka to ka

Answer 18

10^-pka

Question 19

What is the purpose of pka

Answer 19

makes values more manageable than ka and it is much easier to compare relative acid strengths using pka

Question 20

The stronger the acid…

Answer 20

larger the ka and the smaller the pka

Question 21

the weaker the acid…

Answer 21

the smaller the ka and the larger the pka

Question 22

What does [H+] depend upon

Answer 22

concentration of acid and the acid dissociation constant

Question 23

What approximations are made when calculating pH of acids

Answer 23

1. HA dissociates to produce equilibrium concentrations of H+ and A- that are equal.
2. the equilibrium concentration of HA is smaller than the undissociated concentration.

Question 24

How can Ka be calculate used equilibrium concentrations

Answer 24

[H+]eqm[A-]eqm/[HA]eqm or [H+]2/[HA]

Question 25

How to solve pH of a weak acid using Ka

Answer 25

[H+] = square root of (Ka x [HA])

Question 26

What can the ka of a weak acid be determined by

Answer 26

preparing a standard solution of a weak acid of a known concentration. Measuring the pH of the standard solution using a pH meter.

Question 27

What approximations are made involving weak acids

Answer 27

1. Assumes that the dissociation of water is negligible. | 2. The concentration of acid is much greater than the H+ concentration at equilibrium.

Question 28

What is kw

Answer 28

the ionic product of water

Question 29

What is the kw formula

Answer 29

[H+][OH-] = 1x10-14

Question 30

What is the importance of kw

Answer 30

controls the concentrations of H+ and OH- in aqueous solutions

Question 31

How do you calculate H+ and OH- concentrations in aqueous solution when given pH

Answer 31

1. 10^-pH = [H+] | 2. Kw/[H+] = [OH-]

Question 32

What is a strong base

Answer 32

an alkali that completely dissociates in solution

Question 33

What is a monoacidic base

Answer 33

each mole of a base releases one mole of OH-(aq) ions e.g.NaOH

Question 34

How do you calculate the pH of a solution of a strong base

Answer 34

1. concentration of base = [OH-] 2. kw/[OH-] = [H+] 3. -log[H+] = pH

Question 35

What is a weak base

Answer 35

partially dissociates in solution so one mole of a base releases far less than one mole of [OH-]. e.g.NH3

Question 36

How do you find pka form a titration curve

Answer 36

Find volume needed to reach the end point (steep part of the curve). Divide the volume by 2 and use your graph to find the pH. pka=pH