Chemistry - Volumetric Analysis 1 - acid base titrations

equivalence point

where two solutions just react completely with eachother

titration def

procedure where a measured volume of one solution is added to a known volume of another solution until the reaction is complete

analyte

chemical species being analysed to determine its concentration, identities or properties

solution

a perfect mixture of a solute and solvent, the particles are uniformly distributed throughout the solvent

concentration of a solution

amount of solute per amount of solution

percentage weight per volume - aka

grams per 100cm3

% weight per weight, aka

grams per 100g

% volume per volume

volume per 100cm3

parts per illion

1ppm = 1mg/l

standard solution def

solution of known concentration

primary standard

solute/substance that is available in 100% purity, is stable in air, has a high molar mass and dissolves easily in water. Can be made up to a standard solution directly

three examples of primary standards

anhydrous sodium carbonate, sodium carbonate and sodium chloride

secondary standard

solute not available in 100% purity, is NOT stable in air, has a LOW molar mass, and is not easily soluable i water and cannot be made up to a standard solution directly

4 examples of secondary standard solutions

sodium hydroxide, potassium manganate 7, iodine, sodium thiosulfate

why is sodium hydroxide not a primary standard

deliquescent

deliquescent meaning

absorbs moisture from air to form a solution

why is potassium manganate 7 a secondary solution

• decomposes in strong sunlight

• not available in pure state

• does not dissolve readily in water

why is iodine a secondary standard solution

undergoes sublimation

sublimation meaning

changes from solid to gas without a liquid stage

why is sodium thisulphate a secondary standard solution

not available in 100% purity

to standardize meaning

to find the concentration of a solution by titration or colorimetry

prepare a solution in a volumetric flask

• weigh solute on a clock glass using an electronic balance

• ALL of the solute is transferred into a volumetric flask and made up to an ACCURATELY KNOWN VOLUME

why must the solute be made up to an accurately known volume

• concentration can be calculated

• enough solution to carry out atleast 3 titrations

how to make ip a solution of known value, given mass of a solid substance

• if solute is solid, tip it into beaker, wash clock glass several times with deionized water

• rinsings added to beaker and stirred with a clean dry glass rod until it dissolves

• solution poured into volumetric flask using a funnel

• beaker, funnel and rod are rinsed several times with deionized water until the level of the solution is a cm before the mark on the neck of the flask

• deionized water is added drop by drop until THE BOTTOM OF THE MINISCUS is on the graduation mark when READ AT EYE LEVEL

  • stopper invert the flask around 20x to ensure homogenous solution

why is the volumetric flaks inverted 20 to 30 times

solution has a concentration gradient, inverted to make the solution homogenous

how to transfer liquid solute into a volumetric flask

properly rinsed pippette to measure out exact voolume

transfer to flask by TOUCHING THE TIP INSIDE the flask

how to clean a pippette

wash it w deionized wate,r then rinse it with the solution it is to contain to prevent diltion of the solution

why must solutions ne at room temperature when using a pipette

liquid expands on heating and contract on cooling and could make things inaccurate

how to fill a pipette filler

use a pipette filler until the level of liquid is above the mark on the stem of the pipette

allow liquid to run out into a waste beaker until the bottom of the meniscus is on the graduation mark when read at eyelevel

transfer solution into the conical flask by touching the tip of the pipette against the flask

why use a pipette filler to fill the pipette

solutions may b poisonous

how to prepare a ocnical flask

rinse ONLY with deionized water before the solution from the pipette is placed in it

how to prepare a burette

clamped vertically using retort stand to prevent parallax error

rinse with deionized water and then w the solution its gonna contain

use a funnel with the tap closed to fill it to above the 0cm graduation mark, allow solution out until the BOTTOM of the meniscus is on the 0 graduation mark WHEN READ AT EYE LEVEL

remove funnel

ensure hte bit below the tap is full

how to prepare a liquid solution

use properly rinsed pippette to measure out exact volume, transfer to the flask by touching tip inside the flask

wash out w deionized water, rinsings added stirred