ch 7

Question 1

systematic error

Answer 1

cannot be eliminated from repeating trials
- faulty balance
- pipette delivering incorrect dosage
- remaining substance in a container which contaminates
- unsuitable indicator used
- mass of primary standard still containing water/hasnt dried fully.
- reading the scale in the wrong way

Question 2

random errors

Answer 2

follow no regular pattern and can be eliminated from repeating trials
- difficulty judging where the meniscus sits on the line
- difficulty judging between 0.1ml scale on a burette
- incorrect decimal places on scale when measuring the mass of a primary standard

Question 3

mistakes

Answer 3

• misreading numbers on scale
• mistakenly using a pipette of incorrect volume
• spilling sample
• incorrectly rinsing glassware

Question 4

how do you correctly rinse the burette and pipette for volumetric analysis?

Answer 4

with the acid or base they will be filled with instead of water because it will dilute the acid/base

Question 5

how do you correctly rinse the volumetric flask for volumetric analysis?

Answer 5

with distilled water because rinsing with the acid or base will introduce unmeasured amounts of solution affecting results

Question 6

what do precise results look like?

Answer 6

close together eg titration values vary by only 0.1ml, making the average within 0.1ml of each titration.

Question 7

what do accurate results look like?

Answer 7

they are close to the accepted value (correct value) and are precise