Summary
Summary Module 3.2.2 Chapter 10 Reaction Rates
- Institution
- OCR
notes on: 1 - reaction rates 2 - catalysts 3 - Boltzmann distribution 4 - dynamic equilibrium 5 - le Chatelier 6 - equilibrium constant (kc)
[Show more]
Seller
Follow
Content preview
10.1 reaction ratesRate of reaction - Measures how fast a reactant is being used up or formed.
- Change in conc of reactant or product in a given time
- Rate = change in conc/time in s.
- Fastest at start of reaction – highest conc of reactant, slows down as reaction proceeds as Theres
less reactants, once used up conc doesn’t change and ror is at 0.
Collision theory - 2 reacting particles collide = reaction but can bounce off and remain chemically unchanged.
- Affective collisions = reaction with right orientation and amount of E (Ea).
- Increase in conc – more particles in same vol = more collisions = faster reaction as they are being
used up quicker.
- Increasing pressure – smaller vol = less space = more collisions = reactions at faster rate.
Monitoring - Monitoring at regular intervals using gas collection.
production of - On graph: draw a tangent and calculate ror using gradient.
gas - Measure mass lost (before and after).
- Graph – mass over time, tangent and use gradient for ror
10.2 catalysts
catalysts - Changes ror without being used up or being changed.
- May react with reactant to form intermediate – or SA for reaction to take place.
- Catalyst is regenerated – provides alternate pathway to lower Ea
Types of - Homogenous - Same physical state as reactants – forms an intermediate to break down to give
catalysts product and regenerates
- Heterogenous – different physical state from reactants, usually solid for gaseous reactants that
are absorbed onto surface of catalyst so product leaves by desorption.
Sustainability - 0% of chemical material use catalyst – increase rate of reaction by lowering Ea – reduces
and economic temperature needed for the process and E requirements.
importance - Less E required = less electricity or fossil fuels = product is faster without damaging environment
whilst increasing profit.
- Economically – using catalyst is beneficial > cost of developing catalytic process.
- Sustainability – use processes with high atom economy and fewer pollutants = less fossil fuels =
cut emission linked to global warming.
10.3 Boltzmann distribution
Boltzmann distribution - Spread of molecular energies in gases.
- Shade on graph is small = more energy than Ea – enough for E to react.
- No molecules have 0 energy, so molecules under curve = number of molecules.
- No max E for molecule – infinity to meet x axis at high E.
At higher temp - Temp increases, average E of molecules also increases so more molecules have higher E.
- T2 – peak is lower but at higher temp as more molecules overcome Ea than T1
- Higher temp – more molecules with E greater than Ea = more collisions = more reactions =
faster rate + increased E.
With catalyst - Provides alternative pathway with lower Ea = more molecules now have E greater than the
lower Ea = more collisions = faster rate of reaction.
10.4 dynamic equilibrium + le Chatelier
Dynamic equilibrium - Rate of forward reaction is equal to backwards.
- Conc of R and P don’t change.
- Dynamic – forward and backward happen at the same time – so conc remains.
- Must be in closed system – so standard conditions are met.
Le chateliers principle - Position of equilibrium = extent of reaction so if conditions change – position changes.
- System readjusts to minimise effect of change.
conc - More products formed – shifts to right so if more reactants – shift to left.
- Using dichromate ions to show shift.
1) add yellow K2CrO4 to beaker with H2SO4 until there is no change – orange colour
2) add NaOH (aq) - turns back yellow.
- Increasing conc of H+ with H2SO4 = increased rate of forward = right shift for more P.
- Increasing OH with NaOH – increases R removed by H – shifts left for more R.
temp - Increase in temp shifts equilibrium – endothermic so change in H is positive.
- Decrease in temp for endothermic – left shift = more reactants.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller saimabegum. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £5.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70055 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now