Volumetric anylsis - theory without larger paragraphs

standard solution

solution whos concentration is accurately known

primary standard

substance which is pure, stable in air, has a high molar mass and can dissolve easily in water to directly make up a standard solution

Why is it not a primary standard? - sodium hydroxide

deliquescent - absorbs water from air to form solution

Why is it not a primary standard? iodine

sublimes close to room temp

Why is it not a primary standard?ammonia

volatile and escapes from solution into gas

What is a titration?

method of determining accurate concentration of a solution by reacting it with a solution of accurately known concentration

Q: How is a conical flask prepared for use?

must be clean and dry

why conical flask instead of beaker

shape allosws two solutions to be swirled without splashing

pipette function

transfer exact volume of solution

how to prepare a pipette for use

rinse with deionizied water, then with solution it will contain

how to fill a pipette

• using a pipette filler, draw solution into pipette until its above grad mark

  • allow some solution to run out into a waste beaker so the bottom of miniscus rests on the grad mark at eye level

Delivering the solution in a pipette into a conical flask/beaker

transferred into conical flask by touching tip of the pipette against the inside of the flask, do not blow out last drop

prepare a burette

rinse with deionized water then with solution it will contain

how ot fill a burette

clamp it vertically, place a funnel on top, pour solution above grad mark, remove funnel, open tap and allow solution out so bottom of mensicus is at 0 when read at eye level

Q: When filling pipettes and burettes with solution, the solution is filled above the mark

before being drained out so the bottom of the meniscus rests on the mark. What is the

reason for this?

• no air bubbles

• tip is filled with solution

Q: Why is a white tile placed beneath the conical flask before a titration?

the endpoint

will be more accurately identified

procedures followed during a titration to obtain an accurate endpoint

• continuously swirl the conical flask

  • use wash bottle of deionized waer to wash down the sides of the conical flask to ensure all solution from burette reacts with the conial flask

Q: Why is it acceptable at this stage to add deionised water to the conical flask despite

taking precautions when filling the pipette and burette to exclude deionised water

– the number of moles of the solute are now present

in the conical flask – adding deionised water at this stage will not change this

why rough titre

further titrations are more accurate and quicker