R2.1 (The amount of chemical change) Flashcards
percentage yield
how much product is actually made form the reactents
percentage yield formula
(actual yield/theoretical yield) X 100
Why percentage yield isnt always 100%
- not all reactents have reacted
- side reactions ight have occured
- final prodcut has to be purified
- human error
green chemistry
aims to look at sustainable design of chemical processes and products
atom economy
percentage of reactents that turned into desirable products used to measure a reactions efficiency at converting its reactents to products
atom economy formula
(mass of atoms in desired product/mass of atoms in reactents) X 100
Titration
used when a solution of a known conc. (titrant) is used to find the concentration of an unknown solution (titrand)
Titration concentration formula
c1 X v1/n1 = c2 X v2/n2
Steps for a titration
- fill fill base in conical flask using graduated pipette and bulb
- add a few drops of phenolphtalein indicator into the conical flask
- transfer acid from a beaker to the burette
- run a rough titration (let acid run through until conical flask liquid turns pink ->colorless)
- condiuct precise titration until concordent values (±0.1)
Back titration
A type of titration used to determine the concentration of a substance which cannot be directly titrated
example: due to solubility reasons
Back titration Methodology
- react the unkown substance with an excess in standard solution (base or acid; lets say in this case acid
- take that solution (excess) and titrate it with a base of known concentration
- Now you know how many moles of base you needed to neutralise the excess acid and therefore you know the amount of moles in the acid
- now subtract the excess moles of the acid from its origninal amount of moles
- now you know how much acid orignially reacted with the unkown substance
- now calculate the amount of moles of unkonw based on the amount of acid that reacted with it
