Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chem > External Revision: Unit 3, Topic 1 > Flashcards

External Revision: Unit 3, Topic 1 Flashcards

(101 cards)

Start Studying
1
Q

Buffer

A

Solutions that resist slight pH change when acid or base added.
Made from weak conjugate pairs.
- weak acid and salt with counjugate base
-weak base and salt with conjugate acid
Neutralise the acid/base added.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Physical Change

A

Change is physical form not composition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Chemical Change

A

Production of new substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Open System

A

Exchanges matter and energy with surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Closed System

A

Only exchanges energy with surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Reversibility

A

Based on activation energy and product advailability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Activation Energy

A

Energy required for reaction to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Irreversible Reactions

A

Forward direction
Reactants to products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Reversible Reactions

A

Backwards reaction
Products can reform reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Energy profile diagrams

A

Represent changes in energy in reaction
Energy required to break and reform bonds in reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Equilibrium and Dynamic Equlibrium

A

Reactants and products are continuously formed thus reaction seems incomplete
Rate of product production equals rate of reactant reformation
Because forward and reserve still occurring = dynamic equlibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Concentration time graphs and equlibrium

A

Concentration of reactants decrease =concentration products increase
Eventually, both level off
This points of constant concentration is equilibrium
As more products produced, more reformed thus never reaches 0
Steeper curve = faster rate
Steeper curve = more made at that point in time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Position of equilibrium

A

Equal rates does not mean equal concentrations
Position of equilibrium compares concentration products and reactants at equilibrium
Lies right = favours product production
Lies left = favours reactant production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Equilibrium position and colour

A

If equilibrium lies towards products which are blue and reactants green, solution will be more blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Summaries Le chats theory

A

When equilibrium disturbed system acts to partially oppose change and restore equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Identify the factors that disturb equilibrium

A

Addition or removal of products and reactants
Temp change
Volume/pressure change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does Adding reactants and products do to Le chats

A

If volume constant, adding reactant or product disturbs equilibrium by INCREASING reactant or product concentration
Le chats means system wants to partially oppose change, by DECREASING concentration of reactant or product.
Reaction favoured in a way to oppose the increase in product or reactant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does collision theory effect adding reactants and products under Le chats?

A

Increase in reactants means more reactant particles, therefore more collisions and potential to have more successful collisions in same time
This increases reaction rate
Increase in Concentration of products causes same outcomes, by increasing rate of reactant reformation
System will reestablish equilibrium, although concentration of added species is still more then at initial equlibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Summarise how Le chats works when removing reactants and products

A

Removal disturbs equilibrium, causing system to favour the reaction producing the removed species
Ex. Remove products = favour forward
Ex. Remove reactants = favour backwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens when adding catalyst to reaction

A

Catalysts help speed up reaction without being consumed
They don’t effect equilibrium position
They reduce required activation energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe effect of concentration on equilibrium using Le chats

A

Increasing concentration is done by adding a substance, which increases the concentration of substance added
Increasing concentration is also done by decreasing volume, which increases concentration of all species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does decreasing and increasing volume to increase and decrease concentration effect equilibrium

A

Decreasing system volume causes immediate increasing in concentration of all species
System favours reaction producing least number particles to decrease concentration

Increasing volume favours reaction producing more particles due to concentration decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does diluting affect concentration and equilibrium

A

Diluting aqueous solutions decreases concentration of all species by adding Solvent
System favours reaction that results In most particles being formed to increase concentration of system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does pressure effect equilibrium

A

Changing volume effects pressure
Decreasing volume increases pressure, thus system favours reaction producing least particles
Increasing volume reduces pressure, thus system favours reaction producing most particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
How does adding inert gas effect equilibrium
It increases pressure of system but does not effect substances As conc of substances don’t change, no reaction is favoured
26
How does temp effect equilibrium
Reactions are exothermic or endothermic Increasing in temp = favour forward in endothermic and backwards in exothermic Decreasing temp = favour backwards in endothermic and forwards in exothermic
27
Explain increasing temp effect on equilibrium with reference to kinetic energy
Increasing temp increases Kinetic energy of all particles in system, therefore: More particles have enough energy to satisfy activation energy No increase in no. Of collisions This causes increase in reaction rate and forwards and backwards
28
Kc
Equilibrium constant
29
What does Kc show and what is the reaction law
Relationship between conc. Of products and reactants at equilibrium It is used to determine which direction a reaction proceeds to reach equilibrium Signals yeild Kc=[products]^a/[reactants]^b Coefficients become powers Conc of solids and liquids are not used as they are constant
30
What are the values that show where we sits
Kc>10^4 equilibrium mixture contains lots of products Kc<10^-4 equilibrium mixture contains lots of reactants Only thing that can impact Kc is temp Exothermic= increase in temp=Kc decrease Endothermic= increase temp=Kc increase
31
Reaction Quotient (QC)
Relationship between conc of reactants and products at any stage Calculated same as Kc By comparing Kc and Qc we can’t elk what needs to happen to reach equilibrium Q>K, reverse reaction preferred until equilibrium reached Q
32
Kc yield and value relationship
High Kc means high yield
33
Rice table
Reaction Initial Change Equilibrium
34
Brownstead-Lowry defintions
Acid = donate protons (H+) Base = accept protons
35
Proton
H+
36
What happens in an Acid base reaction
Exchange of protons from acid to base
37
What is it called when when acids donate multiple protons or one?
Monoprotic = donate one H+ Polyprotic = donate multiple H+
38
Describe the different types of Polyprotic acid donation
Polyprotic acids donate H+ progressively Diprotic acids = 2 1. H2SO4(aq) → HSO4–(aq) + H+(aq) 2. HSO4–(aq) → SO42–(aq) + H+(aq) Triprotic acids = 3 1. H3PO4(aq) → H2PO4–(aq)+ H+(aq) 2. H2PO4–(aq) ⇌ HPO42–(aq)+ H+(aq) 3. HPO42–(aq) ⇌ PO43–(aq)+ H+(aq) The likelihood of H+ donation at each stage decreases as the acids become weaker. Use the ⇌sign to show this
39
Conjugate base and conjugate acid
Conjugate base = Chemical species formed from an acid that has donated a H+ Eg. Product of the acid which donated (like a pair) Conjugate acid = chemical species formed from a base that has accepted a H+ An acid or base and it’s conjugate are called conjugate pairs
40
Amphiprotic
Substance acting acid acid and base Eg. Can either donate or accept H+ Depends of species reacting with it Common example is water HNO3(aq)+ H2O(I) → H3O+(aq) + NO3–(aq) NH3(aq)+ H2O(I) → OH-(aq) + NH4+(aq)
41
What determines acid strength
It’s ability to ionise/dissociate in a solution Usually solution has water as the solvent Eg. How easily acids loose/donate H+
42
Strong acid characteristics
Completely ionise in solution Eg. Readily donate H+
43
Common strong acids
HCl H2SO4 HNO3
44
Weak acid characteristics
Do not completely ionise in solution (don’t readily give H+)
45
Common Weak acids
CH3COOH
46
What determines base strength
It’s ability to accept H+ and thereby ionise
47
Characteristics of strong base
Readily accept H+ from acid in reaction
48
Common strong bases
NaOH KOH
49
Weak base characteristics
Don’t readily accept H+ from acid
50
Common weak base
NH3
51
Difference between concentration and strength
Concentration = measures amount of solute in given solution For acid/base = indicates amount of acid/base in solution Strength and concentration show 2 DIFFERENT PROPERTIES Acid/base can be strong but dilute
52
Dilute
Measure of strength Means reduced strenght
53
Conjugate pair strength trends
Stronger base = weaker conjugate acid
54
Superacids
= acids that are more acidic then SULFURIC ACID ex. Fluorosulfic acid (HSO3F) these are used in production of plastics and petrol
55
Dissociation
Process where molecule or ionic compound separates into smaller particles In ionic compounds, involves compound splitting to anions and cations
56
Kw
Ionisation constant
57
What does Ionisation constant represent
Represents the product of the ions H3O+ and OH- when water self ionises
58
[……]
Concentration
59
What do all aqueous solutions contain
H3O+ hydronium ions OH- hydroxide ions
60
What does water self ionise to form
Hydronium and hydroxide ions
61
What is the expression for ionisation constant of water
Kw= [H3O+] [OH-] = 10^-14 at 25 degrees C
62
What do H3O+ and OH- each equal
10^-7
63
How and why does concentration changes in hydronium or hydroxide affect each other
Kw is constant so one change directly affect other species Eg. In solution containing acid, Lots of H3O is formed, therefore this conc goes up more then 1 Therefore, OH- decreases Eg. In reaction with base, lots of OH-, therefore conc goes up Therefore H3O conc decreases HENCE, CAN USE Kw TO CALCULATE HYDRONIUM AND HYDROXIDE
64
pH formula
pH = −log10 [H3O+] [H3O+] = 10^–pH M
65
What does pH measure
Acidity of solution Calculated based on [H3O+] in solution
66
What pH value do the numbers indicate
• A pH of 7 = neutral solution. • A pH < 7 = acidic solution. • A pH > 7 = basic solution.
67
How does conc hydronium change each pH value
Because it’s a logarithmic scale, a change in pH by 1 changes the concentration of [H3O+] by a factor of 10
68
Acid, alkaline, neutral
Acidic close to 1 Neutral at 7 Alkaline close to 14
69
What does Dissociation constant measure
Measures a substances ability to reversible dissociate in a solution. Can help determine extent of dissociation for an acid or base
70
Ka
Acid dissociation constant
71
What does Ka measure
Helps determine extent of products made during reaction, therefore determine extent of dissociation of acids at particular temp at equilibrium
72
Ka relationship
Large Ka = lots product produced=strong acid
73
Ka for Polyprotic acids
Ka decrease at each stage. Eg. Stage 1 = 9.5x 10^-8 Stage 2 = 1.0 x 10^-19
74
Kb
Base dissociation constant
75
What does Kb measure
Ability of base to dissociate
76
Kb relationship
Kb large = lots product produced = strong base
77
Kb and Ka formula
Both use same formula as Kc Water is NOT included in calculations HA(aq) + H2O(l) ⇌ H3O+(aq) + A-(aq) Ka= [H3O+][A-]/[HA] B(aq) + H2O(l) ⇌ BH+(aq) + OH-(aq) Kb = [BH+][OH-]/[B]
78
Strength and Ka
Strong acids likley to donate, lots of H3O+ formed. Strong acids have high Ka, weak have low Ka
79
Strength and Kb
Since strong bases are likely to accept protons, lots of OH- formed. Strong base has large Kb Weak base have small Kb
80
Why use salt to house conjugate pair in buffer
Due to solubility of sodium which allows relatively comparable amounts of weak acid and conjugate base in solution
81
What happens when using buffer
When base added, OH- ions react with weak acids to form water and conjugate base Prevents pH changing much When acid added, H+ ions react with conjugate base to form water and weak acid As weak acid doesn’t dissociate well, it causes little pH change
82
How does H3O+ affect EQ referencing indicators
When solution acidic and H3O high, there is equilibrium shift to left, causing colour change When solution basic and low H3O+ conc, EQ shifts right, causing colour change Different types indicators cause diff colour change
83
When does indicators change
When Ka = H3O+ HIn(aq) + H2O(l) ⇌ H3O+(aq) + In-(aq) Ka= [H3O+][In-]/[HIn] THEREFORE colour change at [HIn]=[In-]
84
What is pKa
Negative log of Ka
85
When do we use pKa and relationship with strength
To show strength of acid when the Ka is so small Small pKa = stronger acid Colour changes when pKa=pH
86
Volumetric analysis
Analytical technique used to determine conc of solution
87
Steps of volumetric analysis
1. Weigh primary standard 2. Dissolve in small volume deionised water 3. Transfer to volumetric flask 4. Add enough deionised water until calibration
88
What are solutions of known conc and what are they used to calc.
Primary standards Used to determine conc. Of unknown solution
89
What happens in titration
Solution on known quantity (titre) titrated against solution of unknown conc. Based on amount of titre, calculations determine conc. Unknown solution
90
What happens in acid base titrations and what does it depend on
Acid-base with known quntity titrated against acid/base of unknown conc. Titre require to neutralise unknown solution depends on conc. Of unknown and depends on stoichometric ratio at which solutions react
91
Equivalence vs. end point
In acid/base, indicator used to approx when stoich ratio met = equivalence point In acid/base, equivalence point = neutralisation Colour change = endpoint
92
Equivalence point
Point where substances have reacted according to stoic ratio, as per balanced equation
93
Are equivalence and endpoint close?
Endpoint is a drop past equivalence point
94
Titration curve
Graphical representation of pH of solution during titration Can use curve to find equivalence point On graph, it’s point of inflection
95
Equivalence point and titration curve
EqP is different for different strength acids and bases. Strong acid-strong base = 7 Strong acid-weak base = lower the 7 Weak acid- strong base = more then 7 Weak acid-weak base = around 7
96
What is buffer region
Where pH resistant to change Can see buffer region on titration curve Buffer solution added CHECK BUFFERS WITH SIR
97
Half equivalence point
Half content in flask reacted therefore half of acid base neutralised In buffer region As pKa =pH, pOH=pKb
98
What is a neutralisation reaction
When acids and bases react to produce water and salt
99
What happens in dilution
More solvent added but solute amount doesn’t change No. Moles before dilution= no. Moles after dilution CHANGES CONC.
100
Errors effecting titration
Systemic: Constant bias not eliminated by repeating Random: No regular pattern Minimised using averages
101
Accuracy vs. precision
Accuracy= closeness of results to true value Precision= closeness of measured values to each other

Chem (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions