Chapter 21 (Acid, Bases and Buffers)

Question 1

Define Bronsted-Lowry acid

Answer 1

A substance the can donate a proton

Question 2

Define Bronsted-Lowry base

Answer 2

A substance that can accept a proton

Question 3

Give the equation for calculating pH

Answer 3

-log [H+]

Question 4

What are strong acids?

Answer 4

Acids where the H+ ions are completely dissociated

Question 5

How many decimal places should pH value have?

Answer 5

2

Question 6

What is the equation for finding the concentration of H+?

Answer 6

10^-pH

Question 7

What is the ionic equation for water?

Answer 7

H2O(l) ⇌ H+(aq) + OH-(aq)

Question 8

What is the equation used for water and aqueous solutions?

Answer 8

Kw = [H+][OH-]

Question 9

What is the equation used for pure water?

Answer 9

Kw = [H+]²

Question 10

What is the equation for weak acids and buffer solutions?

Answer 10

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

Question 11

What is the equation for a weak acid with nothing else added?

Answer 11

Ka = [H+]²/[HA]

OR

[H+] = √ (Ka x [HA])

Question 12

What is the equation for a half neutralised weak acid?

Answer 12

Ka = [H+]

OR

pH = pKa

Question 13

How do you find pKa?

Answer 13

-log(Ka)

Question 14

How do you find Ka?

Answer 14

10^-pKa

Question 15

What is the equation for the pH of a strong acid?

Answer 15

-log[H+]

Question 16

What is the equation for the pH of a diluted strong acid?

Answer 16

[H+]old x (old vol/new vol) = [H+]

-log [H+}

Question 17

What is the equation for the pH of a strong base?

Answer 17

[H+] = Kw/[OH-]

-log [H+}

Question 18

What is the equation for the pH of a diluted base?

Answer 18

[OH-] = [OH-]old x (old vol/new vol)

[H+] = Kw/[OH-]

-log [H+}

Question 19

What is the equation for pH of a weak acid?

Answer 19

[H+] = √ (Ka x [HA])

-log [H+}

Question 20

What is the equation for pH of half neutralised weak acid?

Answer 20

Ka = [H+]

-log [H+}

Question 21

What is the equation for the pH of water?

Answer 21

√ Kw = [H+]

-log [H+}

Question 22

How do you find the pH of a strong acid and base solution?

Answer 22

1) Calculate moles of H+
2) Calculate moles of OH-
3) Find which is in excess

If H+ in excess

Moles of XS H+/Total volume

-log [H+}

If OH- in excess

Moles of XS OH-/Total volume

[H+] = Kw/[OH-]

-log [H+}

Question 23

How do you find the pH of a buffer solution?

Answer 23

[H+] = Ka x ([HA]/[A-])

-log [H+]

Question 24

How do you find the pH of a weak acid and base solution?

Answer 24

1) Calculate moles of HA
2) Calculate moles of OH-
3) Find which is in excess

If HA in excess

[HA] = (initial OH moles-moles of OH- added)/Total volume

[A-] = Moles of OH- added/total volume

[H+] = Ka x ([HA]/[A-])

-log [H+]

If OH- is in excess

[OH-] = Moles XS of OH-/Total volume

[H+] = Kw/[OH-]

-log [H+]

Question 25

What is the function of a buffer?

Answer 25

Resists small changes in pH when a small amount of a strong acid or base is added to it.

Question 26

What is the value of Kw?

Answer 26

1 x 10^-14