1.9 Rates Flashcards
Experimental methods for determining orders of reaction
Example Reaction 1
2Na(s) + 2HCl(aq) –> 2NaCl(aq) + H2(g)
Example Reaction 2
CH3CH2Br + NaOH –> CH3CH2OH + NaBr
Example Reaction 3
H2SO4(aq) + BaCl2(aq) –> BaSO4(s) + HCl(aq)
Example Reaction 1
2Na(s) + 2HCl(aq) –> 2NaCl(aq) + H2(g)
· Collect hydrogen gas in a gas syringe
· Measure volume of gas produced over time
Example Reaction 2
CH3CH2Br + NaOH –> CH3CH2OH + NaBr
· Can measure [NaOH] as it is an alkali
· Titrate with HCl (or use pH meter)
Example Reaction 3
H2SO4(aq) + BaCl2(aq) –> BaSO4(s) + HCl(aq)
· Precipitate will start to make solution opaque as it is produced
· Could measure opacity of solution
How would you use these two practicals to measure initial rates
- How would you investigate the order of this reaction with respect to the different reactants
- What must be kept constant when repeating this experiment
Why is water added to the reaction mixture
Why can you analyse effect of changing volume of S2O3^2- on rate of reaction instead of calculating the Concentration of it
- at what point in the reaction does the solution turn blue-black
- Why are most of the reactants combined into one container before starting the reaction
- Why is hydrogen peroxide added last to the reaction solution
- Which other reactants could be added last instead of hydrogen peroxide
Show graphs represents zero order, first order and second order for rate against concentration
What is quenching a reaction
Why would you quench a reaction
How can you quench a reaction
Draw graphs of concentration against time for zero order, first order, second order
Step 2
Two No and H2 are in one eqaution
Rate only depends on OH and CH3COCH3, not on Br2
As reaction proceeds, conc of both OH and ketone decrease, so rate decreases over time
Since bromine is used up in reaction it’s conc falls
As rate slows down, gradient of bromine decreases, hence gradient flatter over time
