Rates of reactions

Question 1

Calculation for average rate of reaction

Answer 1

average rate = change in value / time taken

Question 2

What is needed for a reaction to occur

Answer 2

the reactant particles need to collide with a certain amount of energy

Question 3

What can be done to increase the number of collisions between reactant particles and the certain amount of energy?

Answer 3

increasing the concentration

increasing the surface area

increasing the temperature

adding a catalyst, speeds up reactions without getting used up itself. They can be recovered unchanged at the end of a reaction

Question 4

How can the rate of a reaction be increased?

Answer 4

increasing the number of collisions with this energy will speed up a reaction

Question 5

What unit should be used when calculating the rate of reaction when measuring the volume of a gas?

Answer 5

cm3s-1

Question 6

How can one tell a reaction has finished on a line graph?

Answer 6

The line that is plotted becomes horizontal, indicating that even though time is progressing, there is no increase in the mass of gas that is produced

Question 7

What unit is used in the reaction rate formula

Answer 7

gs-1

Question 8

What is the test for CO2?

Answer 8

Co2 turns lime water cloudy

Question 9

What is the test for oxygen?

Answer 9

oxygen should relight a glowing splint

Question 10

What is the test for hydrogen?

Answer 10

hydrogen burns with a pop

Question 11

Why does increasing the concentration of the reactant particle increase the rate of collisions between reactant particles and the certain amount of energy?

Answer 11

as there is more reactant particles in a given volume of space

Question 12

Why does increasing the surface area increase the rate of collisions between reactant particles and the certain amount of energy?

Answer 12

as more of the reactant particles are exposed

Question 13

Why does increasing the temperature increase the rate of collisions between reactant particles and the certain amount of energy?

Answer 13

reactant particles have more energy and more speed so a greater number will collide more often and with greater energy

Question 14

What effect does increasing the particle size have on the rate on a reaction?

Answer 14

As the particle size inceases (i.e. from powder to lumps) the reaction slows down.

Question 15

An experiment to do with gas. During a reaction the mass of the reacting mixture decreases, explain why the mass loss decreased?

Answer 15

loss of gas

reaction vessel not sealed so gas can escape thus mass decreases

Question 16

The rate of a reaction decreases with time, explain why.

Answer 16

the concentration of reactants decrease

the reactant particles are used up as the reaction proceeds thus the rate of reaction decreases

Question 17

what is a catalysts

Answer 17

Catalysts speed up chemical reactions without being used up in the reaction.

Enzymes are biological catalysts. (enzymes)