Rate of reaction

What is collision theory?

In order for a particle to react is must do three things:

1) Collide

2) Have minimum requirement of energy (activation energy)

3) Collide with the correct orientation (right way round)

How does Concentration effect the rate of reaction?

Increase concentration means more particles in the same space therefore more collisions and more successful collisions and the rate of reaction increases.

What happens if we double the concentration?

The number of collisions and the rate of reaction will double.

Does pressure have a similar effect on the rate of reaction as concentration?

Yes, pressure has a very similar effect to concentration on reaction rates, but mainly for reactions involving gases

4 key factor that affect the rate?

- Surface area (space to react)

- Temperature (more movement)

- Concentration/Pressure (more particles in space)

- Catalyst (reduces energy requirement)

How does temperature effect the rate of reaction?

- Particles of more kinetic energy so Collide more frequently

- More particles have at least the minimum required energy to react

How do catalysts effect the rate of reaction?

- Lowers the minimum energy requirement to react

- More particles have at least the minimum required energy

- Increased frequent successful collisions

Increased rate of reaction

How does surface area effect the rate of reaction?

- Increase in SA provides particles with more space to the collide

- Increase the number of collisions

- Increases frequency of successful collisions

- Increases rate of reaction

What is a catalyst?

A chemical that speeds up a reaction by offering an alternate reaction pathway with a lower activation energy requirement.

How do you work out the mean rate using a graph?

By dividing the total change in the y-axis (e.g., mass or volume) by the total time (change in x-axis) over a specific interval.

What's the difference between mean rate and instantaneous rate of change?

While a "mean rate" is an average rate of change over an interval, a tangent is used to find the instantaneous rate of change at a single point.

How do you work out the mean rate using a tangent?

Draw tangent to the curve at specific point, then calculate the gradient of tangent. Gradient is found by creating right-angled triangle using tangent line and dividing change in y-axis by the change in the x-axis.

What are Independent, Dependant and Control variables?

I = Thing that changes

D = Thing being measured

C = Thing that stay the same

(give two or more examples)

Exothermic?

- Hot

- Releases energy to surroundings

(e.g combustion or respiration)

Endothermic?

- Cold

- Absorbs energy from surroundings

(e.g neutralisation or photosynthesis)

Chemical reaction?

- Non reversible

- chemically changes

(e.g combustion, rusting metal)

- only a few are reversible

(e.g decomposition of ammonium chloride)

Physical reaction?

- Reversible

- physically changes

(e.g change of state, ice melting)

- only a few are non reversible

(e.g lighting a match)

What are all six changes of state?

1) Melting (solid to liquid)

2) Freezing (liquid to solid)

3) Evaporation (liquid to gas

4) Condensation (gas to liquid)

5) Sublimation (solid to gas)

6) Deposition (gas to solid)

Mean rate of reaction equation?

Quantity of reactant formed (mass in g or volume in cm3) or quantity of product formed /divided by/ time taken (in seconds)

What unit should mean rate be given in?

cm3/S or g/s

What protection do you use when measuring the increasing volume of gas given off (practical)?

Goggles/eye protection

What is used when measuring the increasing volume of gas given off (practical)?

Gas syringe, conical flask, reaction mixture, bung.

How do you measure the increasing volume of gas given off (practical)?

By collecting the gas and measuring the volume given off at time intervals.

How do you measure the decreasing light passing through a solution?

Add reactants to conical above X then time how long it takes for the X to not be visible.

Why does it go cloudy in the measuring the decreasing light passing through a solution practical?

The reason it goes cloudy is solid sulphur.

What are the sources of error when measuring the volume of gas?

- Gas leakage

- Temperature fluctuations and inaccuracies from equipment like sticky plungers

- Incorrect viewing angle and

mis-viewing

Explain using collision theory what happens to the rate of reaction when the volume of the container the particles are in is increased? (4 marks)

- Increasing volume will decrease pressure

- This causes particles to collide less

- Therefore, the less frequent successful collisions

- rate of reaction decreases

Explain how catalysts affect the rate of reaction using collision theory? (4 marks)

- Catalysts offer an alternative reaction pathway with a lower activation energy

- more particles have the minimum activation energy required

- increase frequent successful collisions

- rate of reaction increases