Rates Flashcards
equation for rate of reaction
mean rate of reaction =
quantity of reactant used
/time taken
mean rate of reaction =
quantity of product formed/
time taken
plot the quantity of product formed over time (on a graph)
https://bam.files.bbci.co.uk/bam/live/content/zbwngk7/medium
https://bam.files.bbci.co.uk/bam/live/content/zbwngk7/medium
what does the gradient/slope of the line show
The slope of the line gives us an idea of the rate of reaction.
The steeper the slope, the faster the reaction
https://bam.files.bbci.co.uk/bam/live/content/zbwngk7/medium
describe what is happening over the course of the reaction
Initially, the reaction is very fast.
A lot of product is being made/formed in a short amount of time
This is because there are a large number of reactant molecules so lots of them are reacting and forming the product
Gradually the slope of the line is becoming less steep
This shows us that the reaction is slowing down, the rate of the
reaction is decreasing
That is because a lot of the reactant molecules have already reacted and turned into products
This means that there are fewer reactant molecules available to react.
At the end, the slope of the line is now zero. The line is flat. At this point the reaction has stopped. All of the reactant molecules have already reacted.
if product was a gas, then what would you measure the quantity in
cm^3
plot the quantity of reactant used over time (on a graph)
https://mmerevise.co.uk/app/uploads/2023/01/mass-of-reactant-1024x676.png
describe what is happening over the course of the reaction
https://mmerevise.co.uk/app/uploads/2023/01/mass-of-reactant-1024x676.png
Initially, the reaction is very fast.
A lot of reactant is being used in a short amount of time
This is because there are a large number of reactant molecules so lots of them are reacting and forming the product
Gradually the slope of the line is becoming less steep
This shows us that the reaction is slowing down, the rate of the
reaction is decreasing
That is because a lot of the reactant molecules have been used and have already reacted and turned into products
This means that there are fewer reactant molecules available to react.
At the end, the slope of the line is now zero. The line is flat. At this point the reaction has stopped. All of the reactant molecules have been used and have already reacted.
In a chemical reaction, 60g of product was formed in 15s.
Calculate the mean rate of reaction
mean rate of reaction =
quantity of product formed/
time taken
= 60/15 = 4g/s
20g of product was formed in 40s, in a chemical reaction
Calculate the mean rate of reaction
mean rate of reaction =
quantity of product formed/
time taken
= 20/40 = 0.5g/s
20g of product was formed in 40s, in a chemical reaction
The mean rate of reaction is 0.5g/s what does this mean
This means that 0.5g of the product is being formed every second
30g of reactant was used in 10s
Calculate the mean rate of reaction
mean rate of reaction =
quantity of reactant used
/time taken
= 30/10
= 3 g/s
30g of reactant was used in 10s
What does this mean
This means that 0.5g of the reactant is being used every second
calculate the mean rate of reaction after 20s using the graph
mean rate of reaction =
quantity of product formed/
time taken
Using the graph, find out the total volume of gas produced after 20s
go up from 20, hit the graph then go horizontally to the y - axis and read the value
then substitute in values
On a rate of reaction graph, the slope of the curve is constantly changing. what does this mean
The slope of the curve is constantly changing.
This tells us that the rate is also constantly changing (the amount of product formed, at every second is constantly changing)
This makes it very difficult to get a clear idea of the rate of reaction at any specific point
calculate the rate of the reaction at 20s - use the graph
Draw a line going up from 20 hitting the curve
Draw a tangent on the curve, which just touches that point
Make sure the gaps on either side are equal
Calculate the gradient of the tangent using the equation change in y/change in x
change in y = 48cm3 -28cm3 = 20 cm3
change in x = 34 s - 10s = 24 s
gradiuent = 20/24 = 9.83 cm3/s
draw lines from change in y and changin x to the axes to show working out