Rates Of Reaction

Question 1

Define rate of reaction

Answer 1

The rate of a reaction measures how quickly a reactant is used up or how quickly a product is formed

Question 2

Model used to explain how different factors affect the rate of a reaction

Answer 2

Collision Theory

Question 3

What must take place for a reaction to happen?

Answer 3

• reactant particles must collide with each other
  (particles=face correct direction)
• the particles must have enough energy for them to react

Question 4

Name for collision that produces a successful reaction

Answer 4

Successful collision

Question 5

Minimum amount of energy needed for a collision to be successful

Answer 5

Activation Energy

Question 6

calculate mean rate of reaction (when you can measure product)

Answer 6

Mean Rate of Reaction= Quantity of Product Formed / Time Taken

Question 7

calculate mean rate of reaction (when you can measure reactant)

Answer 7

Mean Rate of Reaction= Quantity of Reactant Used / Time Taken

Question 8

Measuring mass- rate units

Answer 8

g/m or g/s

Question 9

When is measuring mas useful?

Answer 9

When CO2 is a product which leaves the reaction container

Question 10

Measuring volume- rate units

Answer 10

cm3 s-1 or cm3 min-1

Question 11

When is measuring mass NOT useful?

Answer 11

When gas that leaves= small relative mass (i.e. H2)

Question 12

When is measuring volume useful?

Answer 12

When gas leaves reaction container.

Question 13

How is volume of gas measured?

Answer 13

-gas syringe
OR
-upside down burette
OR
-measuring cylinder

Question 14

GRAPHS- STEEP CURVE VS NOT

Answer 14

the steeper the line, the faster the reaction

fast reactions finish faster than slow ones (seen when line goes horizontal.

Question 15

INCREASE in concentration=?

Answer 15

higher FREQUENCY of successful collisions

= higher reaction rate)(mean energy NO change

Question 16

INCREASE pressure=?

Answer 16

higher FREQUENCY of successful collisions

= higher reaction rate)(mean energy NO change

Question 17

What happens when lump is divided?

Answer 17

• total volume is same
• surface area increases
• surface area to total volume rate increases

Question 18

LARGER SURFACE ARE=?

Answer 18

higher FREQUENCY of successful collisions

= higher reaction rate)(mean energy NO change

Question 19

HIGHER TEMPERATURE=?

Answer 19

higher FREQUENCY of successful collisions as
-particles move more quickly
-energy of particles increases
= PROPORTION of successful collisions increases
(and reaction rate increases)

Question 20

WHAT DOES A CATALYST DO?

Answer 20

• speed up rate of reaction
• does NOT alter the products of a reaction
• is NOT chemically changed or used up in end

Question 21

how much mass of catalyst is needed to speed up reaction?

Answer 21

small amount

Question 22

How do catalysts work?

Answer 22

1. provides alternative reaction pathway w/lower activation energy than uncatalysed reaction
2. DOES increase frequency of successful collisions
3. This is because as energy required= lower, more particles have necessary amount of activation energy

Question 23

Decreasing particle size of reactant=?

Answer 23

-increasing surface area

=higher rate of reaction