Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
31 Cards in this Set
- Front
- Back
|
What do you need to plot a concentration-time graph? |
Continuous measurements taken during the course of the reaction. |
|
|
What is this method of recording called? |
Continuous monitoring |
|
|
What does a concentration-time graph show? |
It shows the change in concentration of a reactant or product with time during a chemical reaction. |
|
|
What can a concentration-time graph be used to deduce? |
The rate of reaction at a given time The half life (t0.5) of a reactant Whether the order of reaction is first order or not |
|
|
How do you find the rate of reaction at time 't' from a concentration-time graph? |
1) Draw a tangent to the curve at time 't' 2) Find the gradient of the tangent |
|
|
What does the gradient of the tangent tell you? |
Gradient at time 't' = rate at time 't' |
|
|
How do you work out the gradient of the tangent? |
Change in y/ change in x |
|
|
How do you find the initial rate on a concentration-time graph? |
Draw a tangent at 0s and work out the gradient |
|
|
What does measuring the initial rate involve? |
Measuring the rate of reaction at time=0, before any significant changes in concentration occur. |
|
|
What is the initial rate of reaction equal to? |
The gradient of the tangent at time=0 |
|
|
What is the half life of a reactant (t0.5)? |
The time taken for the concentration of the reactant to reduce by half |
|
|
How do you find the half life of a reactant on a concentration-time graph? |
You read from the time axis the time taken for the concentration of the reactant to fall to half. |
|
|
What is true for the half life of a first order reactant? |
The half life is independent of the concentration and is constant. ( half life is always constant ) |
|
|
How do you find the rate constant (k) for a first order reaction from a concentration-time graph? |
k = ln2 / t0.5 (half life) |
|
|
What does order 1 look like on a rate-concentration graph? |
It is a straight diagonal line. It must pass through the origin |
|
|
What does this mean? |
Rate is directly proportional to [A], so if [A] is doubled, the rate is doubled. |
|
|
What can be worked out from this graph and how? |
The rate constant (k) can be determined from the gradient of the graph. |
|
|
What does order 0 look like on a rate-concentration graph? |
It is a straight line across (doesn't go up or down). |
|
|
What does this mean? |
Rate is independent from [A], so if [A] is changed, the rate stays the same. The line has 0 gradient. |
|
|
What does order 2 look like on a rate-concentration graph? |
It is a curved upwards line. It must pass through the origin |
|
|
What does this mean? |
The rate is proportional to [A]^2, so if [A] is doubled, rate will increase by a factor of 4. |
|
|
What happens to half life if the reaction is second order? |
It gets larger each time |
|
|
What happens to half life if the reaction is zero order? |
It gets smaller each time |
|
|
What are the units for half life? |
The units of time used |
|
|
What do you need to plot a curve? |
At least 5 points |
|
|
What is the half life of a reaction? |
The average half life |
|
|
Why may 1st order half lives be slightly different? |
Experimental error |
|
|
How can you find k for order 1 on a rate-concentration graph? |
k=gradient |
|
|
How can you find k for order 2 on a rate-concentration graph?
|
k= rate/ [A]^2 |
|
|
How can you find k for order 0 on a rate-concentration graph?
|
k=rate |
|
|
What must you make sure to do when drawing a tangent? |
Label it ! |
