Standard Solution

Question 1

What is a standard solution?

What is the concentration usually given in?

Answer 1

A solution whose concentration is known accurately

Mol/dm3
Or
g/dm3

Question 2

What is most important about making up a standard solution?

Answer 2

The mass of substance is accurately measured and successfully transferred to a volumetric flask

Question 3

Equipment for a standard solution

Answer 3

Balance
Weighing boat
Small beaker
Volumetric flask

Question 4

Method for making a standard solution

Answer 4

Put weighing boat on balance and tare
Weigh required mass, recording to correct number of significant figures
Transfer to Beaker and add distilled water
Use distilled water to wash weighing boat twice
Stir with stirring rod until all dissolved
Transfer to 250cm3 volumetric flask using a funnel
Wash beaker and rod twice into flask
Add distilled water until 1cm3 below mark then fill to mark with teat pipette
Invert flask several times

Question 5

Where do you measure volume of solution from ?

Answer 5

Bottom of meniscus

Question 6

Method for preparing for a titration

Answer 6

Wash burette with solution A
Fill burette with solution A, ensuring ‘jet’ below tap is filled
Read level of solution

wash 25cm3 with B and fill with B to mark
Ensure no air bubbles
Transfer B to conical flask
Add indicator

Question 7

Describe rough run for a titration

Answer 7

Run A into conical flask until colour change
Read level of solution in burette from bottom of meniscus
Record value to nearest 0.05

Question 8

Describe subsequent titration runs after rough

Answer 8

Run A into B until 2cm3 before end point
Use distilled water to wash any drops of solution into conical flask to ensure all reacts
Add A dropwise until colour change
Repeat until concordant results are obtained

Question 9

Define concordant

Answer 9

Results within 0.1cm3 of each other (units required)

Question 10

What is important to remember about readings for a titration?

Answer 10

Does not have to be 0 initially

Does need to be to nearest 0.05

Question 11

What is the colour of phenolphthalein

a) in acid
b) in alkali
c) at endpoint

Answer 11

a) colourless
b) pink
c) very pale pink

Question 12

What is the colour of methyl orange

a) in acid
b) in alkali
c) at endpoint

Answer 12

a) yellow
b) red
c) pale orange