past paper qs wrong Flashcards
what happens when a catalyst is added to a system in dynamic equilibrium
The rates of the forward and reverse reactions increase by the same amount.
The concentrations of the reactants and products do not change.
The value of Kc remains the same
Which statement(s) for the complex ion [Co(NH2CH2CH2NH2)
3]
2+ is/are correct?
1 It has cis and trans isomers.
2 It has optical isomers.
3 It is six-fold coordination.
one anf two
Explain what is meant by the term weighted mean mass
The mean/average mass) taking into account the
relative abundancies of the isotopes
um of (isotopic mass × %abundance)
sum of (isotopic mass × abundance) / total
abundance
A catalyst is used in the production of methanol in equilibrium 1.
State two ways that the use of catalysts helps chemical companies to make their processes
more sustainable and less harmful to the environment
(Reaction can be carried out at) lower temperatures /
lower energy demand
Less (fossil) fuels burnt / less CO2 emissions
A student investigates the reaction between ethanoic acid, CH3COOH(l) and methanol, CH3OH(l),
in the presence of an acid catalyst. The equation is shown below.
CH3COOH(l) + CH3OH(l) -> CH3COOCH3(l) + H2O(l)
(a) The student carries out an experiment to determine the order of reaction with respect to
CH3COOH.
The student uses a large excess of CH3OH. The temperature is kept constant throughout the
experiment.
The student takes a sample from the mixture every 20 minutes, and then determines the
concentration of the ethanoic acid in each sample.
From the experimental results, the student plots the graph below
Explain why the student uses a large excess of methanol in this experiment
To keep [CH3OH] (effectively) constant
OR
Zero order with respect to CH3OH
OR
To ensure equilibrium is far to the right
ALLOW Change in [CH3OH] is negligible
ALLOW rate is independent of [CH3OH]
IGNORE Methanol doesn’t run out/is not limiting
reagent.
what does ln(2)/HL tell me
the rate constant
