chem paper 1 mod 2 Flashcards
define theoretical yield and actual yield
the maximum calculated amount of a product that could be formed from a given amount of reactants
the actual amount of product obtained from a chemical reaction
formula for percentage yield?
actual yield
—————— x 100
theoretical yield
why are yields less than expected?
- incomplete reactions , reaction not left long enough
- some of product is lost
- other unwanted side reactions, some reactants may react to form different products.
the higher the percentage yield =
more useful the reaction is, a high yield means fewer raw materials are used to make the same amount of product. less waste. more profit.
define atom economy
the percentage, by mass, of reactants that are converted into useful products
how to work out atom economy…
relative formula mass of useful product / sum of relative formula mass of all reactants x 100
why is a particular reaction pathway is chosen to
produce a specific product
scientists look at atom economy, yield, rate, equilibrium position and
usefulness of by-products
how to convert from cm3 to dm3
conc =
conc in moles =
divide by 1000
no of moles / volume of solution
conc in g/ rfm of solute
why may fertilisers contain nitrogen, phosphorus, and potassium
nitrogenous fertilsiers..
bc as fertilsers they replace mineral ions needed by plants so they promoto plant growth / increase yields
are a source of soluble nitrogen compounds
how is nitric acid manufactured from ammonia?
its a nitrogenous fertilisers
ammonia + nitric acid —–> ammonium nitrate
oxidation
how is ammonium sulfate produced in a labratory?
small scale, use ammonium solution and dilute sulfuric acid , titration then crys, batch
how is ammonium sulfate produced in a industrial process
large scale, use diff raw materials , several stages, continuous
what is la chateillers principle
when you change the conditions of a reversible reaction the position of the equilibrium will shift to try and counteract the change.
in industrial reactions, including the Haber
process, conditions used are related to:
avail and £ of r.m
control of temp, press and catal used shud produce an acceptable yield in an acceptable am of time.
using la chatiellers principle how can the rate of equilb be affected
changes in temp , pressure , conc and use of catalyst
