10.1 Reaction rates

Question 1

Definition of rate of a chemical reaction?

Answer 1

How fast a reactant Is used up 
or 
how fast a product is formed
or 
Change in concentration of a reactant or a product in a given time

Question 2

Features of a reaction rate?

Answer 2

Rate of reaction is always fastest at the start of the reaction since high conc.

Reaction slows down as reactants are used up and con. decrease

Once all reactants are used up, the conc. stops changing and rate = 0

Question 3

What does a concentration-time graph look like?

Answer 3

Concentration of product (y)
Time taken (x)

Steep in the beginning;
Less steep near middle;
Straight line parallel to x in the end

Question 4

Name 4 factors that can change the rate of a reaction

Answer 4

Concentration (or pressure when reactants are gases)

Temperature

Use of a catalyst

Surface area of a solid reactant

Question 5

What does the collision theory suggest?

Answer 5

Two reacting particles must collide for a reaction to occur

Question 6

What normally happens in terms of collisions and reaction?

Answer 6

Only a small proportion of collisions result in a chemical reaction

But normally, most molecules just bounce of each other and so no reactions happen

Question 7

What is an effective collision?

Answer 7

A collision that leads to a reaction

Question 8

What conditions have to be met for a collision to be effective?

Answer 8

Particles must collide with the correct orientation

Particles must have sufficient energy to overcome the activation energy barrier of the reaction

Question 9

Does the rate of reaction increase of decrease when concentration is increased?

Answer 9

Increased

Question 10

Why does the rate increase when conc. is increased?

Answer 10

More particles in the same volume

therefore closer together and collide more frequently

Question 11

Why does rate increase when gas pressure increases?

Answer 11

Same number of gas molecules occupy a smaller volume

so more collisions

Question 12

How can a chemical reaction progress be followed?

Answer 12

Decrease in concentration of reactant

Increase in concentration of product

Question 13

How should rate of reaction of a gas be measured?

Answer 13

Gas collection (increase in conc. of product)

Loss of mass of reactant via balance

Question 14

Where should the water level me on the measuring cylinder for gas collection?

Answer 14

0