Brush Up Flashcards

(61 cards)

1
Q

How do you calculate pH of a buffer solution by mixing an acid and a base?

A

|>Calculate initial n
|>smallest reactant n is used up
|>[H⁺] = Ka x ([HA]/[A⁻])
|>[H⁺] = Kw / (n(OH⁻)/total v.)

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2
Q

An Acidic Buffer is a mixture of?

A

weak acid, HA & one of its salts, A⁻

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3
Q

Two ways of making Acidic buffers?

A

|>Add together weak acid & one of its salts

|>Partially neutralise some weak acid by adding a base

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4
Q

When OH⁻ is added to a basic buffer, what occurs?

A

|>OH⁻ reacts with BH⁺
|>Equilibrium shifts left
|>pH changes are minimised

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5
Q

When acid is added to a basic buffer, what occurs?

A

|>H⁺ reacts with OH⁻
|>Equilibrium shifts right
|>pH changes are minimised

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6
Q

A Basic buffer is a mixture of?

A

weak base, B & one of its salts, BH⁺

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7
Q

Equation for [H⁺] of a buffer?

A

[H⁺] = Ka x ([HA]/[A⁻])

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8
Q

When OH⁻ is added to a acidic buffer, what occurs?

A

|>OH⁻ reacts with H⁺
|>Equilibrium shifts right
|>pH changes are minimised

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9
Q

Two ways of making Basic buffers?

A

|>Add together weak base & one of its salts

|>Partially neutralise some weak base by adding an acid

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10
Q

When acid is added to a basic buffer, what occurs?

A

|>H⁺ reacts with A⁻
|>Equilibrium shifts left
|>pH changes are minimised

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11
Q

Method to make a buffer?

A
|>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
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12
Q

Define: Kw, ionic product of water

A

Kw = [H⁺][OH⁻]

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13
Q

When mixing strong acid & strong alkali

where Base is in excess, [H⁺] = ?

A

[H⁺] = Kw / (n(OH⁻)/total v.)

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14
Q

For weak acids, [H⁺] = ?

A

√Ka[HA]

assuming: HA = HA
[H⁺] = [A⁻]

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15
Q

When mixing strong acid & strong alkali

where Acid is in excess, [H⁺] = ?

A

[H⁺] = n(H⁺)/total v.

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16
Q

the Most Reactive Metals have the

____ Eᶿ values?

A

Most Negative

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17
Q

if Concentration of Ions in the Left Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____

A

Shifts Right
Less Negative
Decreases
Cell has smaller difference in E

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18
Q

if Concentration of Ions in the Right Half-Cell
Decreases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____

A

Shifts Left
Less Positive
Decreases
Cell has smaller difference in E

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19
Q

if Concentration of Ions in the Right Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____

A

Shifts Right
More Positive
Increases
Cell has bigger difference in E

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20
Q

if Concentration of Ions in the Right Half-Cell
Increases, equilibria ____
E¹⁄₂cell becomes ____
Ecell ____ because ____

A

Shifts Left
More Negative
Increases
Cell has bigger difference in E

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21
Q

the Most Reactive Non-metals have the

____ Eᶿ values?

A

Most Positive

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22
Q

Define: Standard Electrode Potential

A

e.m.f of a half cell compared with a standard hydrogen half-cell
Measured under standard conditions

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23
Q

Reduction occurs at the ____ electrode?

A

Positive

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24
Q

Equation for: mole fraction of a gas

A

Mole fraction = moles of gas in mixture/
of a gas total n of all gases in mixture

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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
Define: Enthalpy of Lattice Formation ΔLFHᶿ
Enthalpy Change when One mole of Ionic Substance is formed from its Gaseous Ions
31
Forming bonds is ____ ?
Exothermic | Energy is Given out
32
As Charge Density Increases, ΔLDH ____?
becomes less Exothermic
33
Lattice Dissociation Enthalpies are ____ because bonds ____?
Endothermic | Bonds are being Broken
34
As Charge Density Decreases, ΔLDH ____?
becomes more Exothermic
35
As Charge Density Decreases, ΔLFH ____?
becomes less Exothermic
36
As Charge Density Increases, ΔLFH ____?
becomes more Exothermic
37
Why are ionic compounds w/ Exothermic Enthalpy Changes of Solution more likely to Dissolve?
More energy is Released when Ions are Hydrated than is needed in Dissociation
38
Define: Enthalpy of Hydration ΔhydHᶿ
Enthalpy Change when One mole of Aqueous Ions is formed from One mole of Gaseous Ions
39
For Born-Haber cycles, Endothermic reactions are represented by ____?
Arrows pointing up
40
As Charge Density Increases, ΔhydH ____?
becomes less Exothermic
41
As Charge Density Decreases, ΔhydH ____?
becomes more Exothermic
42
Why is a Compromise temp of 450°C used?
High for Fast Rate | Low for Increased Yield
43
As a reaction occurs, the rate ____ as conc. of reactant ____?
Decreases | Falls
44
Why is using Mean Bond Enthalpies less accurate than Hess' Law?
Mean average is used | Assumption all reactions are gaseous
45
Two examples of Endothermic reactions?
Thermal decomposition of CaCO₃ | Photosynthesis
46
Equation to calculate ΔH in KJmol⁻¹
ΔH = q(x10⁻³ if q in J) / mol
47
What is Calorimetry?
Method to determine Enthalpy changes by experiment, converting temp. change of water to quantity of heat energy
48
Define: Bond Enthalpy
Energy Required to break | One mole of a given Covalent bond in gaseous molecules
49
Define: Enthalpy
Heat energy stored in a chemical system
50
How much does Hydrogen Bonding increase water's b.p.t by?
about 200°C
51
Charge of Sulfate(IV) ion?
SO₃²⁻
52
Charge of Nitrate(III) ion?
NO₂⁻
53
Charge of Nitrate(V) ion?
NO₃⁻
54
Charge of Sulfate(VI) ion?
SO₄²⁻
55
Shape and Bond Angle: Water?
Trigonal Pyramidal | 107°
56
Steps to find conc. of a solution of a base?
|>Fill a burette w/ standard solution of acid |>Pipette known volume of base into conical flask |>Add a few drops of indicator |>Add solution until indicator changes colour |>Record volume to the nearest 0.05cm³ |>Perform rough titration, then accurate ones to calculate mean from concordant values
57
Steps for making a standard solution?
|>Dissolve a known mass of solid in Deionised Water |>Using a funnel, transfer into a volumetric flask, including washings |>Make up to a certain volume |>Invert to mix contents
58
Stages of Electron Bombardment Ionisation
|>Vapourise |>Fire high energy Electrons at sample using electron gun |>knocks off electron
59
Stages of Electrospray Ionisation?
|>Dissolve sample in volatile solvent |>Pass through a fine needle to create mist |>Apply high voltage to tip of needle |>Sample gains H⁺
60
How to calculate no. of moles of water of crystallisation?
|>Need to know mass of hydrated & anhydrous salts |>Mass of water = mass hydrated - mass anhydrous |>Work out no. of moles of anhydrous salt & of water |>Find simplest ratio
61
Equation for Ar?
Σ(mass x abundance of each isotope)/ | total abundance