2.2 Rates of reaction

Question 1

What equation is used to calculate the initial rate of reaction from a straight lined graph?

Answer 1

pick a convenient point on the graph ,P, from there draw a straight line to the Y axis ,MP, and then draw a vertical line if needed from M to the beginning of the slope N. Then the equation - N-M/P-M is used.

Question 2

What equation is used to calculate the initial rate of reaction from a curved lined graph?

Answer 2

since the line is curved, a tangent must be drawn where time = 0 and then the gradient of the tangent is calculated. N-M/P-M

Question 3

What are the five factors that affect the ROR?

Answer 3

• Concentration/Pressure
• Temp
• Particle size/Surface area
• Catalysts
• Light

Question 4

What is the equation for the enthalpy change of reversible reactions?

Answer 4

activation energy for forward reaction - activation energy for back reaction

Question 5

Why do some molecules have less energy and move slower than others?

Answer 5

When two have collided the one that caused the collision will move slower and the one that got bumped will move quicker.

Question 6

In a boltzmanns distribution graph what happens when theres an increase in temp?

Answer 6

Graph flattens more and shifts to the right

Question 7

In a boltmanns graph what is different when a catalyst is added?

Answer 7

The Ea (activation energy shifts to the right.

Question 8

What is a homogenous and heterogenous catalyst?

Answer 8

Homo- A catalyst with the same physical state as the reactants
Hetero- A catalyst with a different physical state as its reactants.

Question 9

What different things can be used to measure the ROR?

Answer 9

• Gas syringe (volume of gas)
• manometer (moles)
• weighing scales (change in mass)
• colorimeter (concentration of colour change)

Question 10

Explain the Iodine clock:

Answer 10

Iodine ions can be oxidised to iodine at a measurable rate. Iodine gives a strongly coloured blue complex with starch solution but if a given amount of thiosulfate ion - with which iodine reacts very quickly - is added, no blue colour will apear until enough iodine has been formed to react with all thiosulfate. The time taken for this thus acts as a ‘clock’ to measure the rate of iodine ions being oxidised.