5.1 RATES,EQUILIBRIUM & PH Flashcards
1
Q
Define rate of reaction
A
- Change in concentration of a reactant or product per unit time
2
Q
Define order
A
- The power to which the concentration of a reactant is raised to in the rate equation
3
Q
What does rate constant, K link?
A
- Links rate of reaction with concentration of reactions raised to their orders
4
Q
State the rate equation
A
5
Q
Define overall order
A
- The sum of the individual orders in the rate equation
6
Q
Define half life (of a reactant)
A
- the time taken for the concentration of a reactant to reduce by half
7
Q
Define rate-determining step
A
- the slowest step of a multi-step reaction that determines the rate at which the overall reaction proceeds
8
Q
What is meant by a reactant in zero order?
A
- The rate is unaffected by changing concentration of that reactant
9
Q
What is meant by a reactant in first order?
A
- The rate is directly proportional to the concentration of that reactant
10
Q
What is meant by a reactant in second order?
A
- The rate is equal to the change in concentration squared of that reactant
11
Q
State which reactant order does NOT appear in the rate equation
A
- Zero order reactants
12
Q
Draw all the orders on a concentration-time graph
A
13
Q
Draw all the orders on a rate-concentration graph
A
14
Q
State how the rate of reaction would be determined from a concentration-time graph that produces a curved line of best fit
A
- A tangent to the curve at given point
- Find the gradient using Δconc/time taken (=Δy/Δx)
15
Q
Define half-life
A
- The time taken for the concentration of a reactant to reduce by half
16
Q
State and explain which type of rate graph we identify the half life for
A
- Concentration-time graphs of FIRST ORDER reactants
- Because the half life is independant of concentrations so each half life is the same length
17
Q
State the equation that links half-life with rate constant K
A
18
Q
State how to work out initial rate from a concentration-time graph
A
- Draw a tangent at t=0 and work out the gradient (Δy/Δx)
19
Q
State the relationship between reactants in the rate-determining step and the reactants in the rate equation
A
- Only and all of the reactants that appear in the rate equation must be in the rate-determining (slow) step
(im unsure if this is right, look at ur notes, hivi)
20
Q
State the arrhenius equation
A
21
Q
State what the arrhenius equation links
A
- Links activation energy and temperature to the rate constant K
22
Q
State the reason for use of a colourimeter
A
- Monitors visual colour changes
23
Q
Define continuos monitoring
A
- Taking measurements of rates at specific intervals to measure the change in quantity of a substance
24
Q
Explain the effect of temperature of the rate constant and hence, the rate of reaction
A
- As temperature increases, more KE given to particles
- Thus, more frequent successful collisions with sufficient energy to exceed activation energy
- This increases the value of the rate constant and therefore also the rate of reaction
25
State how we get rid of the **exponential eˣ** in the **arrhenius equation**
- We **natural log** (**ln**) BOTH sides of the equation
26
State which **two parts** of the **arrhenius equation** we can be asked to determine **graphically** AND state the **new** **rearranged** **arrhenius equation** we would use
1) **Activation energy Ea**
2) **Arrhenius constant A**
27
State the **arrhenius equation** after it has been **natural logged** (**ln**)
28
Define **homogenous equilibrium**
- **Equilibrium** where **all species** making up **reactants** and **products** are in the **same physical state**
29
Define **heterogenous equilibrium**
- **Equilibrium** where the **species** making up **reactants** and **products** are in the **different physical states**
30
State what we do if we need to determine a **Kₚ or Kc expression** for a **heterogenous equilibrium**
- **NEVER** include **solid** and **liquid species**
- (Only **gaseous** and **aqueous**)
31
State what the **ICE** table stands for and which questions we use it in
**Initial moles, Change in moles, Equilibrium moles**
- Use in any type of **equilibrium** questions
32
State the **Kc expression**
33
Define **partial pressure**
- The **pressure** an **individual gaseous substance** would **exert** if it occupied the whole reaction vessel alone
34
Define **total pressure**
- The **sum** of **all individual pressures** (**partial pressures**)
35
Define **mole fraction**
- The **proportion** of a **given substance** present in a **reaction mixture**
36
State the formula for **partial pressure**
37
State the formula for **total pressure**
38
State the formula for **mole fractions**
39
State the **Kₚ expression**
40
State what a value of **1** for **Kc** or **Kp** would indicate
- That **equilibrium** **lies** in the **middle**
41
State what a value **greater** than **1** for **Kc** or **Kp** would indicate
- That **equilibrium** **lies** toward the **right**/**products**/**forward**
42
State what a value **less** than **1** for **Kc** or **Kp** would indicate
- That **equilibrium** **lies** toward the **left**/**reactants**/**backward**
43
Define a **bronsted-lowry** **acid**
- A **proton donor species**
44
Define a **bronsted-lowry** **base**
- A **proton acceptor species**
45
Define **monobasic**, **dibasic** and **tribasic acids**
- **Monobasic acid** means each **molecule** releases **one proton** (e.g **HCl**)
- **Dibasic acid** means each **molecule** releases **two protons** (e.g **H₂SO₄**)
- **Tribasic acid** means each **molecule** releases **three protons** (e.g **H₃PO₄**)
46
Define **conjugate acid-base pair**
- A set of **two species** that turn into **each other** by the **gain** or **loss** of a **proton**
47
What does the **acid dissociation constant, Ka** measure?
- The **actual extent** of **acid dissociation**
48
State the **Kₐ expression** then simplify it.
49
State the **two** expressions that convert between **Kₐ** and **pKₐ**
50
State what a **large Kₐ value** indicates
- A **large Kₐ value** means a **large extent** of **acid dissociation**
- The **acid** is **strong**
51
State what a **small Kₐ value** indicates
- A **small Kₐ value** means a **small extent** of **acid dissociation**
- The **acid** is **weak**
52
State what a **high/low** **pKₐ** value indicates
- **High pKₐ** means a **weaker acid**
- **Low pKₐ** means a **stronger acid**
53
State the **two** expressions that convert between **pH** and **[H⁺]**
54
State what a **pH** change of **1** would increase **[H⁺]** by
- A **pH** change of **1** increases the **[H⁺]** by **10 times**
55
Define **strong acid** and draw an **equation**
- An acid that **fully dissociates** in **aqueous solution** to release **H+ ions**
56
Define **weak acid** and draw an **equation**
- An acid that **partially dissociates** in **aqueous solution** to release **H+ ions**
57
State the **assumption** made for **strong monobasic acids**
We assume:
**[H⁺] = [HA]**
58
State the two **assumptions** made for **weak monobasic acids**
We assume:
1) **[H⁺] = [A⁻]**
2) **[HA] undissaociated = [HA] equilibrium**
59
State the **Ka expression** for a **strong monobasic acid**
60
State the **Ka expression** for a **weak monobasic acid**
61
State the equation to find **[H⁺]** of a **weak acid**
62
Explain the **limitation** of assumption used for **weak acids**
- We assume that:
**[HA] undissaociated = [HA] equilibrium**
- However for **"stronger" weak acids** that **dissociate** more than **5%** we cannot use the assumption above
- This is because **"stronger" weak acids** would have a **higher Ka value** than we calcuated, we are **underassuming**
63
State the **reaction** for **ionisation** of **water** and state where **equilibrium lies**
- **Equilibrium** lies well to the **left**
64
State what the **ionic product** of **water Kᵥᵥ expression** determines
- The **relative** **concentrations** of **H+** and **OH-** of an **aqueous solution**
65
State the **Kᵥᵥ expression**
66
State the **assumption** made for **pure water**
We assume:
**[H⁺]=[OH⁻]**
67
Define **alkali**
- A **water soluble base** that **dissociates** to release **OH- ions** in solution
68
State **three** **strong alkalis**
1) **NaOH**
2) **KOH**
3) **Ca(OH)₂**
69
State a **weak alkali**
**NH₃**
70
State the **assumption** we make for **strong monobasic alkalis**
We assume:
**[OH⁻]=[NaOH]**
71
State the equation to find **[H⁺]** of a **strong monobasic alkali**
72
Define **buffer solution**
- A **mixture** that **minimised pH changes** on **small additions** of **acids** or **bases**
73
State what a **buffer solution** is made of
- A **weak acid**, **HA**
- Its **conjugate base**, **A⁻**
74
State the **three** ways of making a **buffer solution**
1) A **solution** of **weak acid** + a **solution** of its **salt**
2) A **solution** of **weak acid** + its **solid** **salt**
3) An **EXCESS** **solution** of **weak acid** + an **alkali** (**partial neutralisation**)
75
State the **reaction** for a **buffer mixture** and state their **relative proportions**
76
Describe the **dissociation** of **salts** thus, state the **assumption** we make
- Salts **fully dissociate** into its **cations** and its **anions** when in **water**
We assume:
**[Salt]=[A⁻]**
77
State the equation to determine the **[H⁺]** of a **buffer solution**
78
Explain the effect of adding **acid** to a **buffer solution**
(**CONJUGATE BASE REMOVES ADDED H⁺**)
- **[H⁺] increases**
- The **conjugate base A⁻** reacts with the **added H⁺ ions**, to form more **acid HA**
- **Equilibrium** shifts to the **left**, **removing** the **added H⁺ ions**
79
Explain the effect of adding **alkali** to a **buffer solution**
(**CONJUGATE BASE REMOVES ADDED H⁺**)
- **[OH⁻] increases**
- The **small concentration** of **H⁺** reacts with the **added OH⁻ ions**, to form more **water molecules**
- **HA dissociates** to **restore** the **lost H⁺**
- **Equilibrium** shifts to the **right**, **removing** the **added OH⁻ ions**
80
Explain the role of the **carbonic acid-hydrogen carbonate buffer solution**
- **Healthy** blood pasma is **7.35** to **7.45**
- **carbonic acid-hydrogen carbonate buffer solution** controlls **blood pH**
- **hydrogencarbonate ions** can **remove acidic** stuff released into the **blood** by converting into **carbonic acid**
- **Enzymes** then convert this to **aqueous carbon dioxide** then into **gasesous carbon dioxide** which is then **exhaled** in the **lungs**
81
Define **equivalence point**
- The point where the **volume** of **one solution** has reacted exactly with the **volume** of the **second solution**
82
Explain how to **calibrate** a **pH probe**
- **Rinse** the **probe** in **deionised water**
- **Blott dry** and place into **solution** of **known pH**
- Leave it to read and ensure it reads the **correct pH**
- **Repeat** with **pH 4/7/10**
83
State what an **indicator** is and how it works
- An indicator is just a **weak acid** (**HIn**)
- It has **one colour** as a **weak acid** and **another colour** as a **conjugate base**
84
Define **endpoint**
- When there are **equal concentrations** of **weak acid** and **conjugate base**
- The **colour** of the **endpoint** is **midway** of the indicators **two colours**
**[HIn] = [In⁻]**
85
State how to pick a **suitible indicator**
- the **end point** of the **indicator** needs to have a **pH value** as **close** as **possible** to the **equivilence point pH value** of the **titration**
86
Draw out the **four** types of **titration curves**
87
Explain why **no indicator** is suitible for a **weak acid-weak base titration**
- Because there literally is **no equivalence point**
88
Do **catalysts** **increase** **concentrations** of **reactants/products**
- **NO** catalysts have **no effect** on **equilibrium concentration**
- (They only **increase** rate of **attainment** of **equilibrium**)
89
Do **catalysts increase** the **Kc value**
- **NO** catalysts have **no effect** on **equilibrium concentrations**
- (They only **increase** rate of **attainment** of **equilibrium**)
90
State the formula to determine **pre-exponential factor A** from **lnA**
