Volumetric Analysis

Question 1

What is the colour of methyl orange in acid?

Answer 1

Red

Question 2

What is the colour of methyl orange in base?

Answer 2

Yellow

Question 3

What is the colour of methyl orange at its end-point?

Answer 3

Orange

Question 4

What is the colour of screened methyl orange in acid?

Answer 4

Purplish-red (Magenta)

Question 5

What is the colour of screened methyl orange in base?

Answer 5

Green

Question 6

What is the colour of screened methyl orange at its end point?

Answer 6

Grey

Question 7

What is the colour of phenolphthalein in acid?

Answer 7

Colourless

Question 8

What is the colour of phenolphthalein in base?

Answer 8

Red

Question 9

What is the colour of phenolphthalein at its end point?

Answer 9

Pink

Question 10

pH interval & type of methyl orange

Answer 10

Strong Acid - Weak Base

Question 11

pH interval & type of screened methyl orange

Answer 11

3-5 & Strong Acid - Weak Base

Question 12

pH interval & type of phenolphthalein

Answer 12

8-10 & Weak Acid - Strong Base

Question 13

Why is screened methyl orange preferred over methyl orange?

Answer 13

Due to the more distinct colour change at end point for screened methyl orange.

Question 14

What is the precision of burette?

Answer 14

~0.05cm^3

Question 15

What is the precision of weighing balance?

Answer 15

2dp

Question 16

What is the precision of measuring cylinders?

Answer 16

0.5cm^3

Question 17

Procedure Part 1: Dilution

Answer 17

1. Using a 50.00cm^3 burette, transfer __ cm^3 of Reagent A in a 250cm^3 volumetric flask.
2. Top up the solution with distilled water to the 250cm^3 mark.
3. Shake well to obtain a homogenous solution. Label this solution FA1.

Question 18

Procedure Part 2a): Preparation of the standard solution of soluble solid Y

Answer 18

1. Weigh accurately about X g (2d.p.) of Solid Y into a dry clean weighing bottle.
2. Dissolve the solid using distilled water (soluble solid) in a 100cm^3 beaker.
3. Transfer the solution after ensuring all the solid has dissolved. Rinse the beaker with water and transfer all washings into a 250cm^3 volumetric flask to ensure quantitative transfer (transferred what you have measured without loss).
4. Top up the solution with distilled water to the 250cm^3 mark.
5. Stopper and shake well to obtain a homogenous solution. Label this solution FA1.

Question 19

Procedure Part 3: Titration

Answer 19

1. Pipette 25.0cm^3 of the FA1 into a 250cm^3 conical flask.
2. Add 2 to 3 drops of ____ indicator.
3. Fill the 50.00cm^3 burette with XX mol dm^-3 Reagent C.
4. Titrate the FA1 against the reagent C solution, Swirl continuously during the addition of the titrant.
5. Towards the end-point, add reagent C dropwise and swirl. Stop the addition until the indicator changes from ______ to _______.
6. Repeat the titrations until the titre volumes are consistent (+-0.10cm^3).