Required Practical 7

Question 1

How can the initial rate of reaction be calculated?

Answer 1

By drawing a tangent when time is equal to 0

Question 2

How can the initial rate of reaction be represented as?

Answer 2

1 / t

Question 3

What is the method for the ‘Iodine Clock’ reaction?

Answer 3

Put each of the chemicals needed in separate burettes

In each experiment, measure out required volumes of the potassium iodide, sodium thiosulphate, starch and water into a small conical flask from the burettes

Measure out the hydrogen peroxide in a test tube, and pour it into the conical flask and immediately start the timer, stirring the mixture

Time until the first hint of blue/black colour appears

Question 4

How can you determine the order of a certain reactant in the Iodine Clock experiment?

Answer 4

By repeating the experiment several times and varying the concentration of a reactant e.g. KI and keeping all of the reactants at the same concentration

Question 5

How is the end point of the Iodine clock reaction seen?

Answer 5

The solution turns from colourless to blue/black

Question 6

By what method can the rate of reaction be calculated throughout an experiment?

Answer 6

A continuous monitoring method can be used

Question 7

What does the gradient represent on a concentration-time graph?

Answer 7

The rate of reaction

Question 8

By what methods can continuous monitoring be measured?

Answer 8

Change in the volume of gas

Change in mass

Colorimetry

Measuring change in electrical conductivity

Measurement of optical activity

Question 9

What is the method for calculating the continuous rate of reaction when a gas is produced?

Answer 9

Measure 50cm³ of 1.0 mol dm⁻³ of hydrochloric acid and add to a conical flask

Set up the gas syringe in the stand

Weigh 0.20g of Magnesium

Add the magnesium ribbon to the conical flask, place the bung firmly into the top of the flask and start the timer

Record the volume of hydrogen gas collected every 15 seconds for thee minutes