chemical changes and structure and rates of reaction

Question 1

Explain the collision theory.

Answer 1

For a reaction to occur the reactant particles must come into contact, or collide with each other. The more collisions that occur, in a given time, the faster the reaction.

Question 2

When there is low temperature, what is the rate of reaction like ?

Answer 2

The particles are moving slowly, resulting in very few collisions in a given time. The reactions is slow.

Question 3

When there is a high temperature, what is the rate of reaction like?

Answer 3

The particles are moving quickly, resulting in many collisions in given time.The reaction is fast.

Question 4

why do substances move about faster when they are heated?

Answer 4

They have more kinetic energy.

Question 5

What is the concentration of a solution?

Answer 5

The measure of the number of particles of a solute in a given volume of solvent.

Question 6

What does the word “mole” mean?

Answer 6

The measure of the number of particles of a substance there are.

Question 7

When there is a dilute solution (low concentration) , what is the rate of reaction like?

Answer 7

There are a small number of moles of solute in a certain volume of solvent.This results in very few collisions and the reaction is slow.

Question 8

When there is a concentrated solution (high concentration) , what is the rate of reaction like?

Answer 8

There are a greater number of moles of solute in the same volume of solvent. This results in more collisions and the reaction is fast.

Question 9

Why does particle size/surface area have an effect on the rate of reaction?

Answer 9

when a solid reacts, it is only the particles on the surface area of the solid which come into contact with the other reactant.

Question 10

what is the rate of reaction like when there is a large particle size?

Answer 10

The large particle size has a small surface area and limited contact with the other reactant. Therefore few collisions take place between the two reactants and the reaction is slow.

Question 11

What is the rate of reaction like when there is a small particle size?

Answer 11

The small particle area has a large surface area and much greater contact with the other reactant.Therefore many collisions take place between the two reactants and the reaction is fast

Question 12

What are the two ways you can monitor the rate of a chemical reaction?

Answer 12

By the change of mass and the change of volume of gas.

Question 13

When is the concentration of reactants the highest?

Answer 13

At the start.

Question 14

Why does the concentration of reactants decrease with time?

Answer 14

The reactants are being used up.

Question 15

What does the gradient of the curve mean?

Answer 15

The slope of the curve.

Question 16

What gas escapes through the cotton wool in the mouth of the conical flask?

Answer 16

Carbon dioxide.

Question 17

What system is used for the method of gas collection?

Answer 17

Gas syringe.

Question 18

What is the units for measuring concentration change?

Answer 18

mol l-1

Question 19

What is the units for measuring gas volume change?

Answer 19

cm3

Question 20

What is the units for measuring mass change?

Answer 20

g

Question 21

What is the unit for measuring seconds?

Answer 21

S-1

Question 22

What is the unit for measuring minutes?

Answer 22

min-1

Question 23

What is the unit for measuring hours?

Answer 23

hr -1

Question 24

Name four factors that increase the rate of reaction.

Answer 24

Increasing the concentration of reactant(s).
Increasing the temperature of the reactant(s).
Decreasing the particle size of the reactant(s)- only affects reactions involving a solid reactant.
The use of a catalyst.

Question 25

How can the average rate of reaction be calculated?

Answer 25

the average rate of reaction=
change in quantity of chemical divided by time interval for change.
(can be found in data booklet)