Rate of reaction

the effect of concentration, including the

pressure of gases, on the rate of a reaction, in

terms of frequency of collisions

EQ

Which statement explain why reaction rate increases as temp increases MC

Greater proportion of molecules have energy greater than activation energy

Collisions between molecules are more frwuqbve

Concentration time graph, using collision theory explain why the gradient decreases over time

Concentration decreases, collisions are less frequent

Explain why this catalyst is described as a heterogenous catalyst for this reaction

The catalyst is in different state to reactants

Catalyst is a …(solid/liquid/gas) whilst reactant is a … (solid/liquid/gas)

Explain using a Boltzmann distribution model why the rate of reaction increases in the presence of a catalyst

Draw a Boltzmann distribution model label Ea and behind it is E catalyst

Explanation: catalyst provides a lower activation energy, more molecules/ greater proportion of molecules have energy above activation energy, greater area under curve above activation energy

Marking points for a Boltzmann distinction curve

Curve starts at origin

Not touching x- axis at higher energy

X-axis: energy

Y-axis: number of molecules

Student plans to compare rate of decomposition of H2 O2 using different metal oxides as catalyst , suggest 2 variables that should be kept constant

Amount of catalyst/ metal oxide

Surface area of catalyst

Temp, pressure

Volume/ concentration/ moles of H2 O2 (reactant)

Explain the role of a catalyst referring to enthalpy profile diagram

Catalyst lowers activation energy, allows reaction to proceed via a different pathway

Catalyst increases rate without itself changing, more molecules/ particles exceed activation energy

Add a second curve to show Boltzmann distribution at higher temp, explain why Boltzmann distribution shows the rate of a reaction is affected by temp

At a higher temp, more molecules have energy greater than Ea, greater area under curve above Ea

The graph shows that the reaction gets slower over time and eventually stops explain in terms of collision theory why that happens

Over time concentration (acid/ reactant) decreases

Less frequent collisions, fewer collisions per second

Reaction eventually stops : reactant has been used up

ASK JAMES ABOUT HOW TO DRAW WHEN THE EXPERIMENT IS REPEATED AT HIGHER TEMP

marking points: slope is steeper, levels off earlier, same loss in mass so levels off at the same mass (same y axis) don’t forget that

Describe the two difference the student would observe between the test tubes, one contains a catalyst and the other doesn’t

The solid dissolves/ disappears faster

More vigorous bubbling

Explain how a catalyst increases rate of reaction

Catalyst lowers activation energy by providing an alternative route

A greater proportion of molecules have more energy greater than activation energy

Why is it difficult to classify the catalyst as a homogenous or heterogenous catalyst

Reactants have different physical states

Explain the effect of increasing the pressure on the rate of reaction

Increasing the pressure increases the rate of reaction, particles are closer together, more particles per unit volume, more particles in the same volume, more frequent collisions, more collision per second/ unit time

Explain why use of catalyst reduces energy demand and benefits environment

Lower temperatures

Less fossil fuels

Reduces CO2 emissions

State an example of a catalyst used by chemical industry and write equation for the reaction is catalyses

Iron

N2 + 3H2 —→ 2NH3

State 2 ways use of catalysts helps chemical companies to make their processes more sustainable and less harmful to environment

Lower temps and pressure can be used/ lower energy demand/ less fossil fuel used/ reduces CO2 emission

Different reactions can be used with greater atom economy, less waste

Catalysts are often enzymes generating specific products

Describe and explain the change in the rate of reaction during the first 200 seconds of experiment

Rate of reaction decreases

concentration decreases, reactants are used up (concentration of reactants decreases)

Less frequent collision , fewer collisions per unit time

Graph of mass (g) against time (s) for reaction of SrCO3 and nitric acid outline a method used to obtain results plotted on graph, answer should include apparatus required and procedure for experiment

Apparatus: beaker or flask, stopwatch, balance

Record mass at time intervals

Intervals stated between 10-50s

Explain why the use of a catalyst can reduce the energy demand

Allows reactions to take place at lower temps

Describe and explain the effect of decreasing the pressure on the rate of a reaction

Decreasing the pressure decreases the rate of reaction , decreases concentration of molecules , less molecules per unit volume , less frequent collisions

The use of catalysts in industrial processes can be beneficial to environment state one reason for this

Catalyst lowers energy demand for reaction

Less combustion of fossil fuels and therefore lower CO2 emissions

Allows different reactions to take place with greater work economy , less waste

Allows less toxic chemicals to be used