Titration And Standard Solution Practical 2

Question 1

What is the purpose of a titration?

Answer 1

To find the concentration/volume of an unknown acid or alkali

Question 2

Purpose of a burette?

Answer 2

Delivers the variable volume of a liquid and contains the standard solution

Read at 2DP where the last digit is a 0 or a 5

Question 3

What is a pipette?

Answer 3

Accurately delivers a stated volume of a liquid

Question 4

What is a standard solution?

Answer 4

A solution whose concentration can be precisely determined and used in later titrations

Question 5

What’s the function of a conical flask?

Answer 5

Contains solution of unknown concentration

Question 6

What is a titre?

Answer 6

Difference between initial and final readings from burette

Question 7

What are concordant results?

Answer 7

2 values within 0.2cm³ away from each other

Question 8

Titration-Preparing a standard solution

Answer 8

1.Weigh boat and requires mass of solid
2.Tip solid into beaker and add small volume of distilled water
3.reweigh boat
4.Stir to homogenise solution and solute is dissolved
5.Transfer solution to a volumetric flask
6.Wash beaker,funnel and Rod with distilled water
7.Use a dropper pipette to add volume up until mark
8.Stop the flask and mix by inversion

Question 9

What would happen if conical flask was washed with reagent solution rather than distilled water?

Answer 9

More moles of solution will be present which leads to an overestimate

Question 10

What would happen and explain the effect if droplets of solution from burette was left on the side of the walls?

Answer 10

Droplets didn’t react with solution so less actual volume in volumetric pipette than expected so this will cause an overestimate so more moles of solution calculated

Question 11

What are concordant results?

Answer 11

Results that are within 0.2 away from each other

Question 12

What is accuracy?

Answer 12

How close your results are to the original value

Question 13

What is precision?

Answer 13

How close all your results are in comparison to each other
More varied results means lower precision

Question 14

What is Dilution?

Answer 14

Process by which solvent is added to a solution to increase its volume and decrease solute conc
Only the volume changes

Question 15

What would happen if you did not reweight the weighing boat during titration?

Answer 15

Some mass may be left on the boat so actual mass in burette is lower leading to an overestimate
As you think you’ve put a higher amount

Question 16

What would happen if volume was not added to the mark?

Answer 16

Inaccuracy as adding too much volume means the concentration changes which means no standard solution

Question 17

What colour does methyl orange go from?

Answer 17

Red to yellow in alkali
Yellow to red in acid

Question 18

What are random errors and how to improve accuracy?

Answer 18

Random errors are caused by unpredictable changes in conditions such as temp or pressure
Improve accuracy by: repeating experiment and removing anomalies

Question 19

What is a systematic error and how to improve?

Answer 19

Error caused by the apparatus and leads to recorded value being to high

Recalibrate or replace the apparatus

Question 20

What would happen if there was a bubble in the pipette containing NAOH and what error would it be?

Answer 20

Random error
Will affect volume of NAOH as there is less volume than you think so underestimate as there is less moles of NAOH

Question 21

What would happen of funnel was left on top of the burette and what error would this be?

Answer 21

Random error,this would increase the vol of acid so the titre is smaller as initial vol of greater so its an underestimate

Question 22

What would happen if the tap of the burette was not filled?

Answer 22

Random error as greater volume of NAOH was actually used so more moles of naoh leading to an overestimate

Question 23

What is the measurement uncertainty of a burette?

Answer 23

±0.05vm³ and for a measuring cylinder as well

Question 24

What is the calculation of percentage uncertainty?

Answer 24

Total error(uncertainty of apparatus)/quantity measured
Than times by a 100 for a percentage

Question 25

Why should the total error sometimes be multiplied by 2 in percentage uncertainty?

Answer 25

As some apparatus require it to be read twice like a burette or a ruler or a mass balance

Question 26

How to minimise error and uncertainty?

Answer 26

Use best type of uncertainty,calibrate
Measure out a greater quantity of susbstance

Question 27

Explain the steps of a back titration?

Answer 27

Weigh a precise amount of the sample
Add a known excess of a standard reagent that fully reacts with the analyte(unknown reagent)(This is a neutralisation reaction)
Mix thoroughly and allow reaction to complete
Titrate the remaining unreached reagent(the one in excess)with a second solution
Calculate amount of reagent that reacted with the analyte by subtracting the excess
Determine the concentration or quantity of the analyte by using stochiometry

Question 28

Why are back titrations necessary instead of normal titrations

Answer 28

Slow reactions
No clear endpoint
Some substances are volatile
Some substances are insoluble