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I learnt about all the factors of rate of reaction such as concentration,pressure, temperature,catalyst and surface area. I also learnt about the two important method sampling and continuous. In sampling, small samples are taken and it is important to quench to carry out more accurate sample analysis. In continuous the physical properties are monitored over time. I learnt about the two graphs and how to determine the different orders. Lastly i also learnt about the rate equations.

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New things we've learnt :

- the relation of the rate determining step with the rate equation
- the usage of reactant concentration and half lives to find the order of a substance
- the mechanism of homogenous catalysts (pretty simple, self explanatory)
- the mechanism of heterogenous catalysts (adsorption of reactants to the catalyst's surface)

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Rate of reaction: change in concentration over time

Factors affecting rate of reaction

Concentration

Pressure

Surface area

Temperature

Catalyst

Sampling is when small samples of the reaction mixture is taken at various times. Chemical analysis is carried out, and quenching is stopping or slowing down the reaction by cooling the sample in ice.

Continuous is when the physical property of the sample is monitored over a period of time. It uses colorimetry, conductivity meter, dilatometer and gas syringe to measure changes in volume or pressure.

Zero order:

Rate against concentration graph: horizontal line

Concentration against time graph: straight line with negative gradient, half life is decreasing

Its rate is independent of the concentration

First order:

Rate against concentration graph: straight line passing through origin

Concentration against time graph: curve with negative and decreasing gradient, constant half life

Its rate is directly proportional to the concentration

Second order:

Rate against concentration graph: positive quadratic curve

Concentration against time graph: curve with negative gradient, half life is increasing

Its rate is directly proportional to the square of concentration

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▪︎factors affecting rate of reaction:
• concentration - more particles so more collision and rate of reaction will be higher

• temperature - there will be more heat energy which will be converted to kinetic energy and particles will move faster/more so rate of reaction will increase

• catalyst - provides alternative pathway with lower activation energy

• pressure - number or particles per unit vol will increase

• total surface area

▪︎ rate of reaction =

change in concentration/time taken

▪︎ method for following a course of reaction:

1. Sampling

• take small sample at various times

• carry out chemical analysis

• quench - slow down or stop - the reaction with ice

2. Continuous

• monitored the entire time the reaction is taking place

• use calorimetry, conductivity meter or measuring changes in vol or pressure of gas

▪︎ zero order

• it is a straight horizontal line in reaction rate - concentration graph

• rate is independent to the reactant

▪︎ first order

• increasing straight line in reaction rate - concentration graph

• rate is directly proportional to reactant

▪︎ second order

• it is an increasing curved line in reaction rate - concentration graph

• rate is directly proportional to reactant^2

▪︎ half life

• time taken for the reactant to fall to half of the original value

• if the half life is constant it is first order but if different then it is second order

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Reaction Kinetics

Methods to Follow the Course of a Reaction

1. Sampling

samples are taken at intervals of time

involves chemical analysis

reaction needs to be "quenched" with ice or cold water

2. Continuous

changes in physical characteristics are observed

measuring changes in colour, electrical conductivity, volume, or gas pressure

conducting colorimetry, using electrical conductivity meter, dilatometer, or gas syringe

Measuring Rate of Reaction with Graphs

concentration-time graph

creating a tangent

measure gradient by making a large triangle with the tangent

for initial rate make sure it's a tangent, not a line that intersects the curve

Order of Reaction

1. Zero Order

rate-concentration graph is horizontal line across

concentration-time graph is straight line

half-life is decreasing

k

independent of the concentration of the specified reactant

2. First Order

rate-concentration graph is a straight line

concentration-time graph is a curve

half-life is constant

k[R]

dependent on the concentration of the specified reactant

3. Second Order

rate-concentration graph is a quadratic curve/parabola

concentration-time graph is a curve

half-life is increasing

k[R]²

dependent on the square of the concentration of the specified reactant

Rate Equations

cannot be determined by stoichiometric equations

determine through experimentation

rate=k[R] where k is the rate constant and [R] is the concentration of the reactant

rate determining step in a multistep reaction is always the slow step

depends on reactants, not products

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From the lecture on reaction kinetics, I have learnt about:

- rate of reaction =

change in concentration/time taken for this change

- the factors affecting the rate of reaction

concentration

pressure

temperature

surface area

catalyst

- two methods following the course of a reaction

sampling

continuous

- sampling

take small samples of the reaction mixture at various times

chemical analysis will be carried out

"quenched", so stop or slow down reaction by cooling sample in ice

- continuous

the physical property of the mixture is monitored over a period of time

uses colorimetry, conductivity meter, changes in pressure and volume so gas syringe or dilatometer will be used

- rate equations

rate = k[reactant], where k is the rate constant

the equation can only be derived experimentally by calculating how the concentration of the reactants affects the rate of reaction, and not from its stoichiometric equations

learnt how to derive rate equations

- order of reaction

zero order ( with respect to [reactant]^0 )

first order  ( with respect  to [reactant]^1 )

second order ( with respect  to [reactant]^2 )

- graphs for rate against concentration

zero order ( straight horizontal line )

first order  ( straight line passing through origin )

second order ( quadratic curve )

- graphs for concentration against time

zero order ( constant rate of decline )

first order  ( declines in a shallow curve )

second order ( a deeper curve than first order )

- half-life

time taken for concentration of a reactant to become half of its original value

first order has a constant half-life, so easier to differentiate between first order and

It was an overall great lecture — with clear and concise explanations, so it was easy to follow and understand.

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From the lecture, I learnt about
-factors affecting rate of reaction
- method to follow a reaction
1. sampling
- take small sample at various times
- quench (stop/slow down) the reaction
- carry out chemical analysis
2. continuous
- monitors physical properties over time
- use colorimetry, conductivity meter or by measuring changes in volume or pressure of gas

- rate of reaction = changes in conc. / time takes
- 3 order of reactions and its graphs
- half life of the reaction order from the concentration-time graph
- rate equation = k[reactant] ^ (order of reaction)
- rate equations cannot be determined by the stoichiometry equation

Overall, the lecture was very clear, easy to follow and understand.

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In this lecture I have learnt:
- The factors affecting the rate of reaction
- The methods for determining rates of reaction : Sampling and Continuous.
-Sampling method requires chemical analysis and taking small samples at various times.
-Continuous method may use colorimetry, changes in volume, or electrical conductivity. There is no need to do chemical analysis.
- Rate of zero order reactions are independent of the concentration.
- Rate of first order reactions are directly proportional to the concentration.
- Rate of second order reactiosn are directly proportional to the square of the concentration.
- The half-life graphs of zero, first, and second order reactions.
-In rate equations we use experimental values.

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Things I learnt:
- definition of rate of reaction
- 2 methods in observation for the rate of reaction
- continuous
- sampling
- 4 factors that affect rate of reaction
- Temperature
- Catalyst
- Concentration
- Surface Area
- how to calculate the rate constant
- how to determine the order reaction
- Half-life
- Rate equations
- Order reaction and graph

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Rate of reaction is the change in concentration per unit time.

Continuous and sampling
Sampling involves taking samples from chemical reactions by quenching the reaction
Continuous involves measuring physical changes such as color, pressure and conductivity

Concentration, rate and time of equations represented in the form of graphs and how to calculate them. (Gradient.. etc)

Order in reactions
- Zero Order
Rate = k
The rate is zero order with respect to [reactant]^0

First order
Rate = k[reactant]^1
The rate is first order with respect to [reactant]^1

Second order
Rate = k[reactant]^2
The rate is second order with respect to [reactant]^2

Rate constant calculation

We also can use half life to determine if the curve is first order or not

The lecture was good as usual.

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what i learnt:

sampling method:

using chemical analysis

samples are quenched (or slowed down)

samples are taken at intervals throughout the progress of the reaction

continuous method:

monitor the reaction over a period of time

can use colorimetry, electrical conductivity, gas syringe, dilatometer

graphs (rate vs time graphs)

zero order (horizontal line) , rate is the same

first order (straight line diagonally), rate is directly proportional to concentration

second order (curve), rate is directly proportional to concentration squared.

graphs (concentration vs time graphs)

zero order (straight line going down diagonally)

first order (curve)

second order (steeper curve)

how to measure rate of reaction with graphs:

create a concentration-time graph

draw a tangent to the curve and find gradient with it

initial rate follows the tangent, not the graph itself

factors affecting reaction kinetics:

temperature

catalyst

concentration

total surface area

pressure

overall the lesson was great it was very detailed as usual and is very clear

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Today, I learnt about the different factors affecting the rates of reaction, how to measure rates of reactions, as well as ho to graphically measure rates of reactions.

Also learnt (and revised today) about different orders of factors that affect the rate of reaction, and the different graphs to tell apart the orders. ++ constant half times for concentration v time for first orders.

We also learnt about the rate determining step, the slowest step that contained the reactants in the rate equation (which isn't based on stoichiometry btw). Wish we practised more questions on that though, i was too confused the first time.

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Through the lecture, I have learnt the following topics:

1. The factors affecting rate of reaction (temperature, pressure, surface area, presence of catalyst, concentration)

2. Sampling: Small samples obtained while the reaction is quenched to ensure accuracy, and that any retrieval of sample is not impacted by its time interval. The sample is chemically analysed through methods such as titration.

3. Continuous: Physical property of the experiment is monitored without quenching or taking samples. This can be done through colourimetry, electrical conductivity, measuring pressure and volume changes, using gas syringe and dilatometer.

4. Rate of reaction can be measured by drawing tangents to a graph and calculating its gradient.

5. The reaction orders consist mostly of zeroth, first and second order.

6. The rate-concentration graph:

Zeroth order: Straight horizontal line

First order: Straight line with (+) gradient passing through O

Second order: Positive quadratic curve passing through O

7. The concentration-time graph:

Zeroth order: Straight line with (-) gradient

First order: Curve with negative gradient with decreasing magnitude, constant half life

Second order: Similar to first order but starts off more steep and ends at higher [R] value. Half life is not constant but increasing

8. The reaction equation cannot be determined by the overall stoichiometric reaction, and can only be determined through experimental means by changing the concentration of one reactant and observing how it affects the reaction rate (which order).

The lecture was elaborate and concise. Explanation of questions involving experimental values has enhanced my understanding on the topic.

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Rate of reaction is the change in concentration per unit time.

Learnt about
- Continuous and sampling
- Graphs representing the concentration, rate and time of equations
- Rate equations
- Learnt about the order reactions and how to determine them
- learnt how to calculate for rate constant
- We can use half life to determine if the curve is first order or not

Need to revise more on:
- General calculating and getting used to it

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There are a total of 4 factors that affect the rate of reaction ( change in conc. over time): -Temperature
-Catalyst used
-Concentrations
-Surface area

The two methods used in the observation for the rate of reaction are sampling and continuous.

We also learned about concentration over time graphs and the three orders.

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Factors affecting rate of reactions are surface area, concentration, temperature, catalyst

Methods of observations:
Continuous (measuring physical changes)
Sampling (measuring chemical changes)

Graphs of zero, first and second order

Half lives
(decreases for zero order)
(constant for first order)
(increases for second order)

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I learnt that data can be obtained with sampling and continuous methods, the order of the reaction with respect to a reactant, graphs of rate-concentration and concentration-time, how to write the rate equation and equations using half life and how the half life can be used to tell apart some graphs.

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During the lecture i learnt about,
- Factors affecting rate of reaction
- Definition of rate of reaction
- Sampling and continuous
- Rate equations
- The order of reaction and its graph
(rate vs concentration) and (concentration vs time)
- Half- life for each order of reaction

I need to practice questions , review videos and read textbook.

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Rate of reaction = mass/time or change in concentration/time  mol/dm^3

Method for following a course of reaction

sampling: taking small samples of the reaction mixture at various times

continuous: physical property of the mixture is monitored over a period of time

Quench means slow down the reaction

How to slow down the reaction: one example is cooling down in ice

Sampling-> quench-> chemical analysis-> titration

Continuous-> physical-> color, electrical conductivity, pressure/volume

Color- colorimetry

Electrical conductivity- e.c. meter

Pressure/volume- dilatometer/ gas syringe

Not all the reactant will be involved in the rate equation. Reactants that do not affect the equation will not be included in the rate equation.

Graph concentration vs time

Two types of graph: straight down or curve for reactant-> product

Rate equation

rate = k[reactant]

Zero order

Rate = k

The rate is zero order with respect to [reactant]^0

First order

Rate = k[reactant]^1

The rate is first order with respect to [reactant]^1

Second order

Rate = k[reactant]^2

The rate is second order with respect to [reactant]^2

Conclusion: rate is independent to the concentration for zero order

Conclusion: rate is directly proportional to the concentration for first order

Conclusion: rate is directly proportional to concentration square for second order

How to find out which one is first or second order?

if the graph is steeper, that graph is second order

Half life is the time taken for the concentration to become half of its initial value.

If half life is constant then it is the first order reaction.

# data[].attributes.attachment_link.title
LECTURE 15 REACTION KINETICS PART 1 CAIE 9701 CHEMISTRY

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Reviewed on:

sampling and continuous method

finding initial rate (tangent at origin)

rate equations (cannot use stoichiometric equations)

order of reaction

for graph of conc./time, second order has deeper curve and longer tail than first order

to differentiate between first and second use half life, constant half life means it is first order

The lecture was a good recap of the topics we discussed so far, teaching was clear.

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Factors affecting rate of reaction

Concentration

Temperature

Catalyst

Total surface area

Volume

Rate of reaction definition

Change in concentration per time taken for this change (mol dm-3 s-1)

Method for following a course of reaction

Sampling

Taking small samples of the reaction mixture at various times

Carry out chemical analysis

‘Quenched’ to stop or slow down the reaction

By cooling sample in ice

Continuous

Physical property of the mixture is monitored over a period of time

Colorimetry

Conductivity meter

Changes in pressure and volume

Small changes of volume using dilatometer

Rate equations

Rate of the reaction = k x

X is the reactant

K is rate constant

Can only be determined through experiments

Not from stoichiometric equations

Order of reaction

Order of reaction with respect to a particular reactant is the power to which the concentration of that reactant is raised in the rate equation

Graph of rate against concentration

1. Zero-order reaction k

1. No effect towards rate

2. First-order reaction k[R]

1. Directly proportional

3. Second-order reaction k[R]2

1. Quadratic curve

Graph of concentration of reactant against time

1. Zero-order reaction (straight)

2. First-order reaction (curve)

3. Second-order reaction (curve)

1. Curve for second order is deeper than first order

2. Curve for the second order has a relative longer ‘tail’ as it levels off

3. Can distinguish the two curves by determining the successive half-lives

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two methods of obtaining data:
-Sampling: involves taking samples from chemical reactions by quenching the reaction
-Continuous: Involves measuring physical changes such as colour, pressure and conductiviy
-Reaction rate graphs and orders
-Concentration time graphs and orders
Half life
zero order, gradient decreases
first order, gradient is constant
second order, gradient increases

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- factors affecting rate of reaction
- sampling/continuous
- graphs (conc. time/ reaction time)
- rate equations
-order of reaction (zero/first/second)
- unit of K
-rate/conc graph
-half life (used to determine first/second order reaction)
- need to practice more on calculation and reading graphs

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Revised on :
- continuous and sampling analysis
- continuous -> physical
- sampling -> chemical
- continuous : dilatometer, colorimeter, electrical conductivity meter
- sampling -> titration
- zero, first, second order and their graphs ( how to analyze which order )
- half life
- factors affecting rate of reaction ( concentration, temperature, surface area, catalyst, pressure )

Good review of the topics we covered last week