Speed of reaction

Question 1

Rate of reaction definition

Answer 1

• how slow or fast

- chemical change is taking place

Question 2

3 ways to measure rate of reaction

Answer 2

1. mass of reactant used up/time
2. mass of products/time
3. vol of gas produced/time

Question 3

Interpretation of graph

Answer 3

• gradient of slope shows rate of reaction
• greater/steeper = faster
• gradient becomes zero when reaction stops, rate=0
• speed at which product produce decreases
• vol of product increases/time (solid/liquid)
• mass of mixture decreases over time (gas)

Question 4

Collision theory

Answer 4

For a reaction to occur,

1. reacting particles must collide with each other frequently
2. must collide with activation energy

Question 5

What speed of reaction is dependent on

Answer 5

• no. of particles present (more, higher chance of collision)
• type of collision (energetic particles moving at higher speeds, greater chance of collision)

Question 6

5 factors that affect rate of reaction

Answer 6

1. Particle size/SA of solid reactants
2. Conc of aq reactants
3. Temp of mixture
4. Pressure of gaseous reactants
5. Presence of Catalyst

Question 7

Surface area of solid reactant

Answer 7

• smaller size of reactant
• greater SA of contact btwn reactants
• more frequent collisions btwn particles
• more successful collisions per unit time
• faster reaction
• steeper gradient
• e.g. coal dust explosive unlike coal chunks

Question 8

Temperature

Answer 8

• time increase
• reactant particles gain kinetic energy, move faster
• more frequent collisions
• more successful collisions per unit time
• faster reaction
• higher temp : steeper gradient
• food kept in deep freeze compartments (-20c), slow down chemical reactions

Question 9

Pressure of gaseous reactants

Answer 9

• affects only gas are they are compressible
• pressure increase
• reactant particles more crowded and closer
• more frequent collisions
• more successful collisions per unit time
• faster reaction

Question 10

Conc of aqueous reactants

Answer 10

• conc increase
• particles crowded and closer
• more particles per unit vol
• more frequent collisions
• more successful collisions per unit time
• faster reaction

Question 11

Catalyst

Answer 11

• speeds up chemical reaction, remain chemically and quantitatively unchanged at end of reaction
• small amt
• specific in action
• effect can be increases by an increase in SA:V
• can be poisoned by small amts of impurities

Question 12

Effect of catalyst

Answer 12

• increase reaction rate by providing alternative pathway
• lower activation energy
• more reactant particles have energy equal or greater than new lowered Ea
• more effective collisions per unit time
• reaction rate increased

Question 13

Activation energy

Answer 13

• min amt of energy required for particles to react