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Chemistry Module 5 > 5.1.1 How Fast? > Flashcards

5.1.1 How Fast? Flashcards

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1
Q

Rate of reaction definition

A

Change in concentration of a substance in unit time

Unit: mol dm^-3s^-1

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2
Q

On a concentration time graph what does the gradient represent

A

Rate of reaction

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3
Q

How do you calculate rate from a graph

A

Draw a tangent

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4
Q

What is the rate constant

A

K

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5
Q

How do you work out the total order of a reaction

A

Add all the individual orders

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6
Q

What do square brackets mean in a rate equation

A

Concentration

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7
Q

Zero order

A

Concentration has no effect on rate of reaction

Rate= k

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8
Q

First order

A

Rate of reactiln directly proprotional to concentration of A

rate= k[A]

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9
Q

Second order

A

Rate of reaction is proportional to concentration of A squared
rate= k[A]^2

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10
Q

Rate concentration for zero order

A

Line is horizontal
Parallel to the x axis
Rate on y, conc on x axis

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11
Q

Rate concentration for first order

A

Straight line y=x
/ shape
Rate on y, conc on x axis

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12
Q

Rate concentration second order

A

Curved, starts at x and increases exponentially

Rate on y, conc on x axis

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13
Q

What is continuous rate data

A

Data from one experiment where concentration of a substance is followed throughout the experiment

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14
Q

How is continuous rate data processed

A

Plotting data

Calculating successive half lives

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15
Q

How to tell if a reaction is first or second order from a graph

A

Half lives are constant when first order

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16
Q

Rate constant k

A

Units of k depend on overall order of the reaction
Work it out from rate equation
K is independent of concentration and time
Only changes with temperature

17
Q

Calculating a value of k using intial rate data

A

Use one of the experiments and put the values for each concentration into your calculated equation
Rearrange to find k

18
Q

Effect of temperature on rate constant

A

Increasing temperature increases rate constant

Relationship is given by arrhenius equation

19
Q

Arrhenius equation to find k

A

k=Ae^-Ea/RT

20
Q

Rearranged arrhenius

A

lnk = constant - Ea/RT
plot graph ln rate or lnk on y axis
Then 1/T on x axis
Ea = gradient of line x R

21
Q

Concentration time graph zero order

A

\
conc on y
Time on x

22
Q

Concentration time graph 1st order

A

\ but curved slightly
conc on y
Time on x

23
Q

Concentration time graph 2nd order

A

\ quite curved
conc on y
time on x

24
Q

Arrhenius equation units

A 
Ea= kJ/mol
R= kJ/mol/ K
T= K
25
Q

How to measure rates of reaction

A

Measure change in volume of gas
Measure change in mass
Titrating samples of reaction mixture with acid, alkali, sodium thiosulfate
Colorimetry
Measure change in electrical conductivity
Measure of optical activity

26
Q

Measure change in volume of gas

A

Works if theres a change in number of moles of gas in the reaction
Gas syringe

27
Q

Measure change of mass

A

Works if there’s a gas produced which is allowed to escape

Works better with heavy gases such as CO2

28
Q

Titrating samples of reaction mixture with acid, alkali, sodium thiosulfate

A
  1. Small samples removed from reaction mixture
  2. Quench which stops reaction (dilute with water, cooling, add a reagent with one of the reactants)
  3. Titrate with a suitable reagent
29
Q

Colorimetry

A

If one of the reactants or products is coloured then colorimetry can be used to measure the change in colour of the reacting mixtures

30
Q

Measuring change in electrical conductivity

A

Can be used if theres a change in the number of ions in reaction mixture

31
Q

Measure optical activity

A

If theres a change in the optical activity through the reaction this could be followed in a polarimeter

32
Q

Slowest step in the reaction

A

Rate determining step

33
Q

Which step controls the rate of reaction

A

Rate determining step

34
Q

Number of moles of each substance of molecules in slowest step is the same as what

A

The order of reaction for each substance

0 moles of A in slow step means A is zero order

Chemistry Module 5 (7 decks)

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