chemical changes titrations

Question 1

what do titrations allow you to find

Answer 1

exactly how much acid is needed to neutralise a quantity of alkali

Question 2

explain the practical

Answer 2

1-concentration of alkali? use pipette and pipette filter, add a set volume of alkali to conical flask, add 2-3 drops of indicator
2-use funnel to fill a burette with some acid of known concentration,below eye level to not spil over, record initial volume of acid in burette
3-use burette, add acid to alkali a bit at a time, give conical flask a regular swirl, go slow when you think the end point is close (colour change)
4-indicator changes colour when all alkali has been neutralised e.g. phenophtalein is pink in alkaline condition, but colourless in acidic conditions
5- reocrd final volume of acid in burette, use along with initial reading to calculate volume of acid used to neutralise the alkali

Question 3

what is pipette used for

Answer 3

measure only 1 volume of solution
fill pipette to about 3 cm above line then drop the level down to the line

Question 4

what is burette used for

Answer 4

measure different volumes and lets you add solution drop by drop

this is where the acid is

Question 5

what do the marks on the burette show

Answer 5

marks down the side show the volume of acid used

Question 6

what does conical flask contain

Answer 6

alkali and the indicator

Question 7

how to increase accuracy of your titratiom and to spot any anomalies

Answer 7

need several consistent readings

Question 8

why should the first titration be a rough titration

Answer 8

to get an approximate idea of where the solution changes colour- end point

Question 9

why do you repeat experiment a few times

Answer 9

to make sure you get same answer each time (e.g. within 0.10cm ^3)
finally calculate mean of results and ignore anomalous results

Question 10

what is universal indicator used for

Answer 10

to estimate pH of solution bc it can turn a variety of colours
each coloue indicates a narrow range of pH values
it is made from a mixture of indicators so colour gradually changes from red in acidic solutions to violet in alkaline solutions

Question 11

in titration between alkali and an acid
you want to see sudden colour change at end point how do you find this

Answer 11

use a single indicator
e.g. litmus (blue in alkali, red in acid)

phenolphthalein(pink in alkali, colourless in acid)

methylorange (yellow in alkali, red in acid )