Rates Of Reaction

Question 1

Increasing Temperature

Answer 1

Increases KE
More collisions per unit volume
More successful collisions per unit time
Rate of Reaction increases

Question 2

Increasing Concentration

Answer 2

More particles per unit volume
Collision frequency is higher
More successful collisions per unit time
Rate of reaction increases

Question 3

Increase Surface area

Answer 3

more solid is exposed to other particles
Collision frequency is higher
More successful collisions per unit time
Rate of reaction increases

Question 4

What does a catalyst do?

Answer 4

A catalyst provides an alternative route with a lower activation energy

Question 5

Add a catalyst

Answer 5

Frequency of collisions with enough energy is higher
More successful collisions per unit time
Rate of Reaction increases

Question 6

Practical: Reacting Sodium thiosulphate with Hydrochloric acid
Aim: To determine the effect of concentration on rate of reaction

Answer 6

Independent variable - concentration of sodium thiosulphate
Dependent variable - Time take for cross to disappear
Control variables - temperature, concentration of HCl, volume of the solution

Observations - solid sulphur is produced, black cross gradually disappears

Question 7

How is rate calculated?

Answer 7

Rate = 1/ time taken

Question 8

Practical: Reacting calcium carbonate chips with Hydrochloric acid
Aim: To determine the effect of surface area on the rate of reaction

Answer 8

Independent variable - size of calcium carbonate chips
Dependent variable - volume of CO2 produced
Control variables - mass of calcium carbonate, volume and concentration os HCl, temperature

Observations - calcium carbonate chips dissolve in Hydrochloric acid

Equation:
CaCO3 + 2HCl —> CaCl2 + H2O + CO2

Question 9

Practical: Reacting Magnesium with Hydrochloric acid
Aim: to determine the effect of temperature on the rate of reaction

Answer 9

Independent Variable: Temperature of HCl
Dependent Variable: time taken for Mg (s) to disappear
Control Variable: Mass and SA of Mg, volume and concentration of HCL

Observations:
Magnesium solid dissolves

Question 10

What do catalysts do?

Answer 10

Increase rate of reaction
Remain chemically unchanged

Question 11

Practical: Decomposition of Hydrogen Peroxide
Aim: to determine the effect of ac catalyst on the rate of reaction

Catalyst is magnesium oxide - black solid
Catalyst are not included in equation because they are unchanged during the reaction

Answer 11

Independent variable: Catalyst being used
Dependent Variable: Volume of Oxygen produces
Control Variable: Volume and Concentration of Hydrogen peroxide, temperature, mass and surface area of catalyst

Equation:

2H2O2 —> 2H2O + O2