Measuring rates of reaction

Question 1

Equation for rate of reaction

Answer 1

• Amount of reactant used or amount of product formed / time

if product or reactant is gas = cm^3/s
If solid = g/s

Question 2

How many ways are there to measure the rate of reaction?

Answer 2

3 ways

Question 3

Mention the practical for the first way

Answer 3

• Precipitation and colour change
  You can record the visual change in a reaction if the initial solution is transparent and the product is a precipitate which clouds the solution

You can observe a mark through the solution and measure how long it takes to disappear - the faster the mark disappears, the quicker the reaction

• if the reactants are coloured and the products are colurless, you can time how long it takes for the solution to gain or lose colour

Question 4

What’s the issue with practical 1 for precipitation and colour change?

Answer 4

• The results are subjective - diff ppl may not agree at which point the mark disappears or changes colour.
• You also can’t plot a reaction graph from the results

Question 5

Practical 2 - change in mass

Answer 5

• measuring the speed of a reaction that produces a gas can be carried out using a mass balance
• As the gas is released, the mass disappearing is measured on the balance
• The quicker the reading on the balance drops, the faster the reaction

Question 6

What’s the advantages or disadvantages of practical 2

Answer 6

• If you take measurements at regular intervals, you can plot a reaction graph and find the rate quite quickly.
• Most accurate because mass balance is very accurate
• dis = releases gas straight into the room

Question 7

Practical 3 - The volume of gas given off

Answer 7

• This involves usage of gas syringe to measure the volume of gas given off
• The more gas given off during the given time interval = faster the reaction
• Gas syringe usually gives volume accurate to nearest cm^3 so = quite accurate
• you can take measurements at regular intervals and plot a rate of reaction graph

Question 8

Practical 3 - The volume of gas given off - what’s the issue with this practical?

Answer 8

• if the reaction is too vigorous - you can easilty blow the plunger out the end of the syringe