Flashcards in Brush Up Deck (61)
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1
How do you calculate pH of a buffer solution by mixing an acid and a base?
|>Calculate initial n
|>smallest reactant n is used up
|>[H⁺] = Ka x ([HA]/[A⁻])
|>[H⁺] = Kw / (n(OH⁻)/total v.)
2
An Acidic Buffer is a mixture of?
weak acid, HA & one of its salts, A⁻
3
Two ways of making Acidic buffers?
|>Add together weak acid & one of its salts
|>Partially neutralise some weak acid by adding a base
4
When OH⁻ is added to a basic buffer, what occurs?
|>OH⁻ reacts with BH⁺
|>Equilibrium shifts left
|>pH changes are minimised
5
When acid is added to a basic buffer, what occurs?
|>H⁺ reacts with OH⁻
|>Equilibrium shifts right
|>pH changes are minimised
6
A Basic buffer is a mixture of?
weak base, B & one of its salts, BH⁺
7
Equation for [H⁺] of a buffer?
[H⁺] = Ka x ([HA]/[A⁻])
8
When OH⁻ is added to a acidic buffer, what occurs?
|>OH⁻ reacts with H⁺
|>Equilibrium shifts right
|>pH changes are minimised
9
Two ways of making Basic buffers?
|>Add together weak base & one of its salts
|>Partially neutralise some weak base by adding an acid
10
When acid is added to a basic buffer, what occurs?
|>H⁺ reacts with A⁻
|>Equilibrium shifts left
|>pH changes are minimised
11
Method to make a buffer?
|>Weigh accurately Xg of salt (A⁻)
|>In a beaker, dissolve in its acid (HA)
|>Using a funnel, transfer to volumetric flask
|>Include washings
|>Make up to mark with acid
|>Invert multiple times to mix
12
Define: Kw, ionic product of water
Kw = [H⁺][OH⁻]
13
When mixing strong acid & strong alkali
where Base is in excess, [H⁺] = ?
[H⁺] = Kw / (n(OH⁻)/total v.)
14
For weak acids, [H⁺] = ?
√Ka[HA]
assuming: [HA](equilibrium) = [HA](initial)
[H⁺] = [A⁻]
15
When mixing strong acid & strong alkali
where Acid is in excess, [H⁺] = ?
[H⁺] = n(H⁺)/total v.
16
the Most Reactive Metals have the
____ Eᶿ values?
Most Negative
17
if Concentration of Ions in the Left Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____
Shifts Right
Less Negative
Decreases
Cell has smaller difference in E
18
if Concentration of Ions in the Right Half-Cell
Decreases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____
Shifts Left
Less Positive
Decreases
Cell has smaller difference in E
19
if Concentration of Ions in the Right Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____
Shifts Right
More Positive
Increases
Cell has bigger difference in E
20
if Concentration of Ions in the Right Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____
Shifts Left
More Negative
Increases
Cell has bigger difference in E
21
the Most Reactive Non-metals have the
____ Eᶿ values?
Most Positive
22
Define: Standard Electrode Potential
e.m.f of a half cell compared with a standard hydrogen half-cell
Measured under standard conditions
23
Reduction occurs at the ____ electrode?
Positive
24
Equation for: mole fraction of a gas
Mole fraction = moles of gas in mixture/
of a gas total n of all gases in mixture
25
Equation for: Partial Pressure of a gas
Partial Pressure = mole fraction of gas x Total Pressure
of a gas
26
Equation for Gibbs free Energy Change, ΔG?
ΔG = ΔH - TΔS
27
Charge density increases if:
Charge Increases & Size Decreases
Charge Increases & Size is Constant
28
Charge density decreases if:
Charge Decreases & Size Increases
Charge is Constant & Size Increases
29
As Charge Density Increases, ΔhydH ____?
becomes less Exothermic
30
