How science works

Question 1

Disadvantages of using KCN to turn a haloalkane to into an amine

Answer 1

• CN- is very Toxic
• lower yield because 2 steps
• LiAlH₄ is expensive

Question 2

Disadvantages of adding NH₃ in order to convert a haloalkane to an amine

Answer 2

• Further substitutions are likely to occur so the products will be impure
• High pressure is needed which is expensive

Question 3

Uses of long ester salt e.g CH₃(CH₂)₁₇COO^– Na+

Answer 3

• Soap
• Hydrophilic head attracts water
• Tail attracts fats

Question 4

Uses of long methyl esters e.g CH₃(CH₂)₁₉COOCH₃

Answer 4

• BioDIESEL for cars
• To MAKE soaps

Question 5

Use of quaternary ammonium salts e.g )

[C₁₆H₃₃N(CH₃)₃] ⁺ Br ^– .

Answer 5

• Cationic surfactant
• Fabric softener

Question 7

What needs to be done so that the public feel confident that a research conducted is reliable

Answer 7

1 experiment repeated over a long period

2 repeated by other scientists to avoiding bias

3 results made public so other scientists can peer review

Question 8

Why is ethene the preferred reagent instead of chloroethane when making ethylbenzene

Answer 8

• chloroethane usually made from ethene
• chloroethane is more difficult to make
• ethene is a by product of cracking

Question 10

Why are acyl chlorides better than carb acid during production of esters (add alcohol)

Answer 10

• faster
• not reversible so bigger yield
• no acid catalyst required

Question 11

Benefits of using a spectrometer

Answer 11

• Rapid determination of concentration
• Does not interfere with the reaction
• Can measure very low conc

Question 12

Why is using scrap iron to extract copper more env friendly than using C to reduce CuO

Answer 12

• less mining of copper ore so landscape is preserved
• Less energy consumption
• Less CO2 released into the atmosphere

Question 13

Why is ethanol a carbon-neutral fuel?

Answer 13

• Ethanol is extracted from corn crops
• CO2 released by combustion is equal to CO2 taken up in photosynthesis
• So no net carbon dioxide emission

Question 14

How can chromatography be used to test if a substance contains X

Answer 14

• Substance is mixed with a solvent e.g water
• Use column chromatography
• Detect and compare X based on retention time

Question 15

How to distinguish ammonia and methylamine

Answer 15

• Measure pH with a meter
• Methylamine would have a higher pH

Question 16

Advantage of using acid anhydride over acyl chloride

Answer 16

• reaction less violent (exothermic)
• no corrosive HCl fumes formed so safer
• anhydride cheaper as acyl chloride’s are expensive

Question 17

Why is chloroethanoic a stronger acid than ethanoic acid.

Answer 17

• Cl is more electronegative so it withdraws electrons
• This reduces negative charge on COO–
• O―H bond weakened, making it easier for the H⁺ to be released

Question 18

Use of Phenylamine e.g CH₃C₆H₄NH₂

Answer 18

• making dyes
• making detergent

Question 19

In a reaction the % atom economy was 51% and the yield was 74%.

Comment on the viability of the reaction

Answer 19

• Although yield appears satisfactory (74%)
• % atom economy is only 51%
• Meaning nearly half of the material produced is waste and must be disposed of