RP1- Making standard solution + acid-base titration

Question 1

Possible errors in part 1

Answer 1

1. systematic error- balance
2. if anhydrous sodium hydrogesulfate is too old, it will have picked up water–> mass x accurate
3. bottom of meniscus- parallax?

Question 2

Part 1-
Reducing uncertainties in measuring mass

Answer 2

1. ↑ accurate balance/ ↑ mass –> ↓ uncertainty
2. weigh sample before + after adding –> calculate diff. ==> ↑ accurate measurement

Question 3

Safety precautions for titration

Answer 3

• acid & alkali- corrosive
• wear eye protection & gloves

Question 4

Describe a method to add an accurately known mass of solid to a beaker to make a solution. (2)

Answer 4

• measure mass of weighing boat + solid
• add solid to beaker + reweigh weighing boat, - final mass to find mass added

Question 5

A student is required to make 250 cm3 of an aqueous solution that contains an accurately measured mass of sodium hydrogensulfate (NaHSO4).
Describe the method that the student should use to make this solution. (4)

Answer 5

1. weigh + reweigh solid, cal diff –> exact mass
2. dissolve in water in beaker (/ conical flask?)
3. transfer washings into 250cm3 volumetric flask
4. make up to mark + shake to mix

Question 6

Give two practical steps needed before recording initial burette reading. (2)

Answer 6

1. remove funnel
2. ensure jet is filled/ x air bubbles (open tap to fill space below tap)