RP7a - measuring rate of reaction via continuous monitoring method + initial rate Flashcards
If a gas is soluble in water, what is an appropriate way of measuring the gas volume produced in a practical?
Using a gas syringe
If a gas is insoluble in water, what other method can be used to measure gas volume from a practical other than a gas syringe?
Using an inverted measuring cylinder
Describe how you could measure the rate of reaction by finding the volume of hydrogen gas produced when reacting magnesium and HCl
Add a strip of magnesium ribbon into a conical flask containing HCl
Place a bung on the flask connected to a gas syringe/ inverted measuring cylinder and start the timer
Record volume of gas produced every 15 seconds for 3 minutes
What are the errors in the method for measuring gas volume?
Some gas may escape before putting the bung on the conical flask
When putting the bung on, volume of the bung displaces air in cylinder, increasing volume
Surface area of magnesium may affect reaction rate
How can errors in measuring gas volume be reduced?
Place ribbon in test tube within conical flask and swirl to release the ribbon
Suspend ribbon on string so stopper can be loosened enough to let it drop
Why is measuring the change of mass overtime not suitable for hydrogen?
It has a very low formula mass
Why is it difficult to determine rate of reaction for very exothermic reactions?
Higher temp from reaction causes an increase in reaction rate
define quenched
Stopping the reaction
What are some method of quenching?
Rapid cooling
Adding large known volume of water to sample
Neutralising reactant with another chemical
If the solution is coloured, what can be used to measure rate of reaction?
Colorimeter
In a conc vs time graph, if the conc has a linear relationship with time, what is the order of reaction?
0 order
In a conc vs time graph, if there is a constant half life what order is the reaction?
1st order
In a 0 order reaction, when conc doubles what happens to the rate?
No change
In a 1st order reaction, when conc doubles what happens to the rate?
Doubles
In a 2nd order reaction, when conc doubles what happens to the rate?
quadruples
