organic practicals

Question 1

how could you distinguish between the two compounds

Answer 1

1- take melting points of crystal

2- compare to known values

Question 2

Order of practical techniques for purification of organic solid

Answer 2

1- Filtration under reduced pressure

2- Recrystallisation

3- Measurement of melting points

Question 3

Describe the purification step of filtration under reduced pressure (step 1)

Answer 3

1- Dissolve impure solid in minimum volume of hot solvent.

2- Cool solution and filter solid under reduced pressure using Buchner flask.

Question 4

Describe the purification step of recrystallisation (step 2)

Answer 4

1-Dissolve solid in minimum volume of hot solvent.

2- Cool solution and filter solid under reduced pressure using Buchner flask.

3- Scratch with glass rod.

4- Wash with cold solvent and dry.

Question 5

Describe the purification step measurement of melting point (step 3)

Answer 5

1- Measure melting point of crystals.

2- Compare to known value from data book.

3- Pure sample will have sharp melting point very close to data book value.

Question 6

purification method organics 1

Answer 6

1- add a neutralising agent e.g. Na2C03

2- in separating funnel, organic layer is on top

3- drying with an anhydrous salt e.g. cacl2

4- redistill at 44 degrees

Question 7

purification method organics 2

Answer 7

1- recrystlaisition

2- dissolve impure solid in
minmum volume of hot water

3- cool solution and filter solid

4- wash with cold water and dry

Question 8

mg to g

Answer 8

divide by 1000

Question 9

Describe and explain how to prepare a standard solution

Answer 9

1- Weigh mass of crystals in beaker on mass balance to 2dp

2- Dissolve in distilled water

3- Transfer to 250cm volumetric flask

4- Rinse beaker and transfer washings to volumetric flask

5-Make up to mark with more water up to 250cm3, so bottom of meniscus is on mark

6-Use dropping pipette when filling to the mark

7- Put a stopper on top, and invert the flask several times to mix

Question 10

When given the melting point to compare to data book, how do you know if it’s pure

Answer 10

Pure sample will have sharp melting point very close to data book value

Question 11

Stationary phase in TLC chromatography

Answer 11

TLC plate

Question 12

Mobile phase in TLC chromatography

Answer 12

Compound being tested

Question 13

Rf equation

Answer 13

Question 14

Affect of Rf value, the more strongly a compound is absorbed onto stationary phase

Answer 14

Lower Rf value

Question 15

Why is a control spot used sometimes during TLC chromatography

Answer 15

Show the formation of the desired product and show when the reaction has finsihed

Question 16

Purpose of gas chromatography

Answer 16

Seperate compounds based on their relative solubility in the stationary phase

Question 17

What does retention time mean in gas chromatography

Answer 17

How long a component stays in the column

Question 18

What does retention time identify in gas chromatography

Answer 18

Identifies components in a mixture

Question 19

Q
What does relative peak area identifiy in gas chromatography

Answer 19

Proportions of componetns in a mixture

Question 20

What can calibration curves be used for in gas chromatography

Answer 20

Confirm the concentrations of components in a mixture

Question 21

What is the mobile phase in gas chromatography

Answer 21

Carrier gas

Question 22

Answer 22

C

ch3COCl

Question 23

Answer 23

2- nitrophenol and 3 nitrophenol have 6 peaks/ 6 environments

4- nitrophenol has four peaks/ environments

4- an be distinguished

2- nitrophenol and 3 cannot be distinguished

Question 24

Answer 24

Question 25

Answer 25

Question 26

Answer 26

Question 27

Answer 27

Question 28

Answer 28

Question 29

Answer 29

Question 30

a scientist hydrolyse a drug in lab. then analysed the mixture of products using Gc-MS. explain how GC- MS enables products to be identified

Answer 30

separating compounds comparison with spectral datebase

Question 31

explain how chromatography can be used to identify AA. and suggest why only 2 spots and should be 3

Answer 31

1- measure distance moved by spot/ solvent 2- compare Rf values with known values 3- two AA have similar Rf values