Relative Effects On Rate Of Reactions Flashcards
What does the steepness of the gradient of a graph correlate to?
It’s about rate of reactions. The steeper the gradient, the faster the rate of reaction.
What does the height a line/curve reaches correlate to?
It’s about the reacting quantities. The curve/line will be higher when the reaction produces more gas, but only if the Y axis is labelled “volume of gas produced”. If it’s labelled “amount of reactant used up” than the higher the line, the more reactant used up in a reaction.
What different factors can affect the height of a graph?
If it’s product produced, then volume of reactant/amount of reactant and also the concentration of reactant. If it’s amount of reactant used up, it’d just be volume of reactant/amount of reactant.
What factors affect the steepness of a gradient for a graph?
Presence of a catalyst, increase of temperature, concentration of reactant, either small SA:V or a big SA:V.
Why does concentration affect both steepness and height of a curve/line on a graph?
Because as well as speeding up a reaction, the concentration of a reactant also means that more product can be formed in the end, or more of a reactant can be used up because concentration is more particles in a given volume so more particles to use up, and more particles to react with.
How do get a good idea of how much product is formed using concentration of reactant and volume of reactant?
Do conc. times the volume to get a good idea on how much product can be formed. This is probably only for compatible reasons. Like for example a line already on the graph is 2 mol. times 6 cm cubed and you have to plot a line from a reaction with 4 mol. times 3 cm cubed. You can see they’ll reach the same height.
This reaction is between calcium carbonate chips added to a solution of HCL acid. CO2 is the gas produced. We have:
Large chips
Conc. of 2 mol
Volume of 50 cm3
Temp of 20 degrees
No catalyst
What does this mean for steepness and height of line plotted for this reaction compared to a line that has:
Small chips
Conc. of 2 mol.
Volume of acid 100cm3
Temp of 20
No catalyst
Well small chips mean an increase of SA:V so consequently an increase of rate of reaction. 20 degrees is room temp so reaction wouldn’t speed up so much. Concentration is 2 and volume is 100 so gas produced should be around 200 cm3.
Large chips mean a decrease in SA:V so a decrease in rate of reaction. They both have the same temperature and both use no catalyst, but volume for one of them is 50. So 50 times 2 is roughly 100 cm3 of gas produced, which is half of 200 cm3 produced. So, the first line would have a shallower line because of decrease of SA:V and would also reach half of line 2’s height as it only produces half the volume of gas.
This reaction is between calcium carbonate chips added to a solution of HCL acid. CO2 is the gas produced. We have:
Small chips
Conc. of 4 mol
Volume of 50 cm3
Temp of 20 degrees
No catalyst
What does this mean for steepness and height of line plotted for this reaction compared to a line that has:
Small chips
Conc. of 2 mol.
Volume of acid 100cm3
Temp of 20
No catalyst
Both have small chips so both have the same SA:V. Both use 20 degrees of temperature. Both use no catalyst. Now, for line 1, they have a concentration of 4, which means compared to line 2, they have steeper line. However, height wise, 4 times 50 is 200 cm3 of gas produced and 2 times 100 is still 200 cm3 of gas produced. So they produce the same amount of gas so reach the same heights, but line one would be steeper with a higher concentration, so it’d reach the same height faster than line 1.
This reaction is between calcium carbonate chips added to a solution of HCL acid. CO2 is the gas produced. We have:
Powder from chips
Conc. of 2 mol
Volume of 200 cm3
Temp of 40 degrees
There is a catalyst
What does this mean for steepness and height of line plotted for this reaction compared to a line that has:
Small chips
Conc. of 2 mol.
Volume of acid 100cm3
Temp of 20
No catalyst
So powder is has a VERY small SA:V so it had a very fast rate of reaction. Faster than the small chips in line 2. There is a higher temperature used in line 1 then line 2 so line one would have a faster reaction. There is a catalyst used in line one so line one would have a faster reaction.
As for height: 2 times 100 is 200 cm3 of gas produced for line 2 and for line one it’s 2 times 200 for a total of 400 cm3 produced in total. So not only would line one have a WAY steeper line for its gradient, but it’d also reach double the height of line two.
Explain in terms of particles why the rate of reaction is always the fastest at the beginning of a reaction.
At the beginning, the reaction is the fastest. This is because the concentration of reactant/reacting particles is at the highest it would be throughout the whole reaction so that would mean more frequent collisions would occur and a faster rate of reaction would appear as the consequence.
Describe in terms of particles why reactions slow down during the middle and stop at the end.
In the middle, concentration of particles have decreased so less frequent collisions would happen so reaction would slow down. At the end, all the reactants are used up, or at the very least, one reactant is used up. So particles cannot collide so cannot form a reaction.
