Phase Two Titration Year 10 EEI by Mr H Graham

Volumetric analysis is;

A type of chemical analysis which depends on the accurate measurement of solution volumesA titration is a

form of volumetric analysis

Phase Two Titration Year 10 EEI by Mr H Graham

Phase Two Titration Year 10 EEI by Mr H Graham

Phase Two

This Friday we will carry out a titration using a 2g sample of the white powder mix

The white powder contains sodium carbonate. This will be titrated with a standard (known concentration) hydrochloric acid solution. By measuring the volume accurately and by using n = cV we can find the number of moles of hydrochloric acid reacting and by using the reaction ratio find the number of moles of carbonate in the original mix

Phase Two Titration Year 10 EEI by Mr H Graham

BUT!

WHAT DOES A TITRATION LOOK LIKE?

Phase Two Titration Year 10 EEI by Mr H Graham

TITRATION ANIMATION

REQUIRES WEB LINK

HERE

Phase Two Titration Year 10 EEI by Mr H Graham

Titration equipment

pipetteaccurately measures smaller volumes (25mL)

burette a graduated tube with tap. Used to measure volumes of solutions during a titration

Research, How they are used.

Phase Two Titration Year 10 EEI by Mr H Graham

Titration equipmentvolumetric flask

accurately measures a set volume (100mL)

pipette filler

a device that is used to draw solutions safely into a pipette

Research, How they are used.

Phase Two Titration Year 10 EEI by Mr H Graham

ProcedureDissolve two grams of white powder in about 40mL of H2OPour this into a 100mL volumetric flask. Add distilled water so that you get up to the 100mL mark. This solution has an unknown concentration.

Set up a clean burette using a burette stand. Use a funnel and fill this with the hydrochloric acid solution (known concentration 0.1M)

Pipette 20mL of the white powder solution into a conical flask. Add 4 drops of methyl orange indicator (this will turn yellow)

TITRATE by adding the acid solution from the burette into the conical flask. You will notice a pink colour appearing as the acid is added. Proceed slowly

STOP and RECORD the volume of acid

When the indicator changes to all PINK (END POINT)

USE n =c V to find the number of moles of acid added

COPY THIS

Phase Two Titration Year 10 EEI by Mr H Graham

white powder mix has high pH at the start of the titration

by adding acid from the burette the pH drops. The indicator changes when the reaction is complete

Phase Two Titration Year 10 EEI by Mr H Graham

Phase Two Titration Year 10 EEI by Mr H Graham

The unknown Na2CO3 is titrated against an known HCl solution. 20mL of the carbonate is placed in the conical. The known (0.1M) HCl in the burette.

An average titration reading of ? is obtained.

What is the concentration of the carbonate solution?

2H+ + CO3

2- = CO2 + H2O

Consider your titration, we know three key things we need to calculate the acid concentration

a simplified form of the equation, notice the 2 : 1 ratio

Phase Two Titration Year 10 EEI by Mr H Graham

2HCl + Na2CO3 2NaCl +CO2 + H2O

Consider your titration, we know three key things we need to calculate the acid concentration

HCl = 0.1Mvolume ? burette reading

Na2CO3conc unknownvolume =

20mL(0.02L)

Find moles of HCl

Find moles of carbonate in 20mL of solution (half moles of HCl)

Find how many moles of carbonate in 100mL volumetric flask

This is the number of moles in 2g of white powder

Find the number of moles in 5g of powder

Find mass of Na2CO3 in 5g

2 1