U2 AOS2 Chapter 13

Question 1

aliquot

Answer 1

portion of sample used for analysis during titration (solution in flask)

Question 2

concordant titres

Answer 2

three or more titres within 0.1mL from each other

Question 3

end point

Answer 3

point where a colour change occurs during titration

Question 4

equivalence point

Important

Answer 4

where both reactants are mixed in exact stoichiometric ratios; acid and base are neutrilised

Question 5

meniscus

Answer 5

curved upper surface of liquid

Question 6

primary standard

Answer 6

substance used to make a primary standard solution

Question 7

titration

Answer 7

quantitative technique used to find the concentration and/or amount of a solution

Question 8

primary standard solution

Answer 8

solution of precisely known concentration

Question 9

titration curve

Answer 9

plots titre volume vs pH

Question 10

titre

Answer 10

volume of solution delivered from burette

Question 11

uses of titration

Answer 11

testing water samples, measuring the amount of vitamin C in orange juice, determine the acidity of fruit juice

Question 12

titration process summary

Answer 12

react a solution of known concentration from the burette with unknown concentration of the aliquot

Question 13

standard solution preparation steps

Answer 13

1. mass of primary standard weighed
2. primary standard transferred to volumetric flask
3. deionised water added until primary standard is dissolved
4. solution left and swirled to allow for volume expansion of newly formed IMFs
5. deionised water is added until required volume is reached

Question 14

criteria of primary standard solution

Answer 14

• must be pure and stable
• must not react w/ atmosphere, -
• must be soluble
• must be readily available and inexpensive
• must be weighed accurately (high known molar mass)

Question 15

process of titration

Answer 15

1. pipette used to transfer aliquot to conical flask
2. relevant indicator added to flask
3. conical flask placed under burette, burette filled
4. solution dispensed until end point reached
5. volume dispensed is recorded

Question 16

benefit of concordant titres

Answer 16

minimises random error, increases reliability and precision

Question 17

affect results if: burette rinsed w/ water

Answer 17

solution is burette diluted = underestimated = overestimated conical flask solution

Question 18

affect results if: pipette rinsed w/ water

Answer 18

solution in conical flask = diluted = underestimated = overestimated burette solution

Question 19

affect results if: conical flask rinsed w/ solution

Answer 19

solution in conical flask has higher concentration = overestimated = underestimated burette solution

Question 20

affect results if: end point missed

Answer 20

discrepancy between end point and equivalence point = conical flask overestimated, burette underestimated

Question 21

factors of choosing indicator

Answer 21

equivalence point falls within pH range of colour change, know approximate equivalence point for solution (based on strength) = end point and equivalence point as close as possible

Question 22

strong base, strong acid

Answer 22

ions react to same extent, same amount of solution is required equivalence point 7, steep,

Question 23

strong acid, weak base

Answer 23

when mol of solution is equal, concentration of H+ is higher OH-as the acid ions fully dissolve = equivalence point below 7

Question 24

weak acid, strong base

Answer 24

when mol of solution is equal, concentration of OH- is higher tha H+ as the base ions fully dissolve = equivalence point above 7

Question 25

weak acid, weak base

Answer 25

when mols are equal, dissolved ions is equal = equivalence point is 7, softer graph

Question 26

end point vs equivalence point

Answer 26

end point = approximate, ep = exact stoichiometric ratios

Question 27

volumetric flask

Answer 27

highly accurate glassware used to create accurate volume

Question 28

why is it important for a primary standard to be accurate when making a standard solution?

Answer 28

mass of primary standard is used to determine concentration of standard solution

Question 29

in titration, where is the the solution of unknown concentration?

Answer 29

either the burette or conical flask

Question 30

affect results if: water is left in conical flask

Answer 30

no change, titre is based on amount of mols not concentration

Question 31

higher titre

Answer 31

= higher concentration

Question 32

why are solutions diluted before titration?

Answer 32

So as not to use too large a volume of the solution in the burette (or to use and obtain a reasonably sized titre).

Question 33

potential errors in titration

Answer 33

• inappropriate rinsing of glassware = decreasing the accuracy and validity
• Improper preparation of diluted/standard solution
• solutions not standardised/ cannot be standardised
• only stated to one significant figure

Question 34

possible systematic error in titration which could lead to overestimation of conical flask concentration (acid)

Answer 34

pipettes delivering extra acid, equipment for base actually lower than shown, burette delivers less base than shown, scales miscalibrated showing more base than actually there

Question 35

systematic error

Answer 35

a consistent error shifting results from true value in the same direction

Question 36

graph conventions

Answer 36

independent variable x axis, dependent y axis, *remember title