The Student Room Group

Edexcel chemistry - unit 2 19th january 2012

Scroll to see replies

Original post by aqua05
when primary alcohol is heated with dilute H2SO4 & K2Cr2O7, the products formed are carboxylic acid via an aldehyde

When secondary alcohol is heated under reflux, ketone is formed :smile:

MgCl2 is more covalent :smile:

My question:
When doing the experiment under reflux why is it important that it remains open at the top?


if in the exam they say sodium dichromate rather than pottassium dichromate don't be put off by this, because the same oxidation will take place! just a word of advice!

yes when doing reflux you MUST leave the top open, otherwise the pressure will build up and boom!

my question to you is why is mgcl2 more covalent?

cheers man
Reply 61
Original post by James A
if in the exam they say sodium dichromate rather than pottassium dichromate don't be put off by this, because the same oxidation will take place! just a word of advice!

yes when doing reflux you MUST leave the top open, otherwise the pressure will build up and boom!

my question to you is why is mgcl2 more covalent?

cheers man



Mg has a high charge of +2 & Cl is big in size thus Mg can attract electron cloud of the anion(cl-)

Thanks for the advice! i'll take note of that :biggrin: wouldnt have known that if you wouldnt have said :smile:
Reply 62
Another few questions:

1. Define 'carbon neutral fuel'.

2. Explain how a catalyst increases the rate of a chemical reaction.

3. What would you observe when PCl5 is added to propan-1-ol?
(edited 12 years ago)
Reply 63
Original post by Cetacea
Another few questions:

1. Define 'carbon neutral fuel'.

2. Explain how a catalyst increases the rate of a chemical reaction.

3. What would you observe when PCl5 is added to propan-1-ol?


1. A fuel is carbon neutral if the amount of CO2 absorbed when the raw material is grown equals the amount of CO2 produced when it is manufactured and burnt.

2. A catalyst provides an alternative route for the reaction with a lower activation energy. Thus a greater proportion of particles have energy greater than (or equal to) activation energy.

3. Steamy white fumes. (Confirms presence of HCL) and the solution goes from orange to green. (I think).
Reply 64
Original post by 7even
1. A fuel is carbon neutral if the amount of CO2 absorbed when the raw material is grown equals the amount of CO2 produced when it is manufactured and burnt.

2. A catalyst provides an alternative route for the reaction with a lower activation energy. Thus a greater proportion of particles have energy greater than (or equal to) activation energy.

3. Steamy white fumes. (Confirms presence of HCL) and the solution goes from orange to green. (I think).


Great answers! When you say orange to green I think you're thinking of the oxidation of alcohols with acidified potassium dichromate (VI); just stick to the white steamy fumes. Ask me some questions!
Original post by Cetacea

Original post by Cetacea
Great answers! When you say orange to green I think you're thinking of the oxidation of alcohols with acidified potassium dichromate (VI); just stick to the white steamy fumes. Ask me some questions!


Give the balanced equation for the complete combustion of propanol.
Reply 66
Resitting this unit because I got a B in it. It is so dull compared to A2
Original post by aqua05
Hiii can you explain to me this iodine bit reacting with alcohol :frown:
I dont seem to understand it.. thanks :smile:


you don't need the mechanism for it, all you need to understand is that the I will displace the OH group and if it's PI3, a H3PO3 will be formed. That's it.
Reply 68
Hello, just wondering do we need to know any organic chemistry revolving around alkanes or alkenes whatsoever?
Original post by 7even

Original post by 7even
Hello, just wondering do we need to know any organic chemistry revolving around alkanes or alkenes whatsoever?


Electrophilic addition of alkenes.
Reply 70
Original post by 7even
1. A fuel is carbon neutral if the amount of CO2 absorbed when the raw material is grown equals the amount of CO2 produced when it is manufactured and burnt.

2. A catalyst provides an alternative route for the reaction with a lower activation energy. Thus a greater proportion of particles have energy greater than (or equal to) activation energy.

3. Steamy white fumes. (Confirms presence of HCL) and the solution goes from orange to green. (I think).


You can't say steamy white fumes...
only say steamy fumes..
Steamy white fumes are only observed when it is mixed with ammonia
Reply 71
Original post by This Honest
you don't need the mechanism for it, all you need to understand is that the I will displace the OH group and if it's PI3, a H3PO3 will be formed. That's it.


thanks :smile:
Reply 72
Original post by aqua05
You can't say steamy white fumes...
only say steamy fumes..
Steamy white fumes are only observed when it is mixed with ammonia


Nu-uh, white SMOKE is observed on the mouth of the test tube with ammonia. Steamy white fumes in the test tube is correct.
I forgive you.
Reply 73
Original post by nutterfrutter
give the balanced equation for the complete combustion of propanol.


C3H7OH + 41/2O2 --> 3CO2 + 4H2O

One for you: write an equation for the thermal decomposition of sodium nitrate.
Original post by Cetacea

Original post by Cetacea
C3H7OH + 41/2O2 --> 3CO2 + 4H2O

One for you: write an equation for the thermal decomposition of sodium nitrate.


NaNO3 ---> NaNO2 + 1/2O2
Reply 75
Original post by 7even
Nu-uh, white SMOKE is observed on the mouth of the test tube with ammonia. Steamy white fumes in the test tube is correct.
I forgive you.


oh !
sorry about that!
Reply 76
explain what is meant by the term thermal decomposition????
Original post by cisne

Original post by cisne
explain what is meant by the term thermal decomposition????


Break down of one reactant, using heat energy, to form more than one product.
Reply 78
What would you observe if you added potassium iodide to conc. sulphuric acid?
Reply 79
but-2-ene exists as two geometrical isomers, explain why but-2-ene exists as two geometrical isomers. (2 marks)
this is a question from january 2008,though......i cuouldn't find a simple way to answer this,can anybody help me please?

Quick Reply