Chapter 18 - Rates of Reactions Flashcards Preview

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Flashcards in Chapter 18 - Rates of Reactions Deck (22)
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1
Q

What is a reaction’s rate?

A

The change in concentration per second.

2
Q

What is rate measured in?

A

Mol dm^-3 s^-1

3
Q

In a chemical reaction, if A is zero order, what effect would be seen if [A] is doubled?

A

Reaction rate would not change.

4
Q

In a chemical reaction, if A is first order, what effect would be seen if [A] is doubled?

A

Reaction rate would double.

5
Q

In a chemical reaction, if A is second order, what effect would be seen if [A] is doubled?

A

Reaction rate would quadruple.

6
Q

How is the reaction rate at a specific time worked out using a concentration against time graph?

A

At the set time, draw a tangent to the curve and measure the gradient to get the rate.

7
Q

If there are two reactants, A and B, what would be the rate equation?

A

rate = k x [A]^m x [B]^n
k - rate constant
m - order of A
n - order of B

8
Q

What is initial rate?

A

The instantaneous rate at the beginning of an experiment when t=0.

9
Q

In a concentration time graph, and a rate time graph, what would zero order look like?

A

Concentration time - linear to 0 concentration

Rate time - Horizontal line

10
Q

In a concentration time graph, and a rate time graph, what would first order look like?

A

Concentration time - curve getting closer to zero

Rate time - Linear proportional

11
Q

In a concentration time graph, and a rate time graph, what would second order look like?

A

Concentration time - steeper curve

Rate time - proportional to x^2

12
Q

What are the two ways of continuous monitoring when a gas is produced?

A

Gas collection

Mass loss

13
Q

What is a way of utilising light to monitor rate?

A

Using a colourimeter.

Measuring the amount of light absorbed by a solution.

14
Q

What is half life?

A

The time taken for half of a reactant to be used up.

15
Q

In a concentration time graph, how can you deduce whether the reactant is first or second order?

A

Measure multiple half lives.
If the half life is constant, it is first order.
If the half life is increasing, it is second order.

16
Q

If the rate is only affected by one reactant, which is first order, what is another way of determining the rate constant?

A

k = ln|2| / t(1/2)

17
Q

What is a reaction mechanism?

A

A series of steps that, together, make up the overall reaction.

18
Q

What is the rate determining step?

A

The slowest step in the reaction mechanism of a multi-step reaction.

19
Q

Why does temperature affect the rate constant?

A

Increasing the temperature, increases rate of reaction and thus rate constant.

20
Q

What is the Arrhenius equation?

A

k = A x e^(-E(a)/RT)
A - pre exponential factor
-E(a)/RT - exponential factor

21
Q

What is the logarithmic form of the Arrhenius equation?

A

ln|k| = -E(a)/RT + ln|A|

22
Q

What can the log form of the Arrhenius equation be modelled as?

A
A straight line graph in y=mx + c
ln|k| is y
-E(a)/R is m
1/T is x
ln|A| is c