Edexcel chemistry - unit 2 19th january 2012
Chemistry exam discussion - share revision tips in preparation for GCSE, A Level and other chemistry exams and discuss how they went afterwards.
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Re: Edexcel chemistry - unit 2 19th january 2012if 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!(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
MgCl2 is more covalent
My question:
When doing the experiment under reflux why is it important that it remains open at the top?
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 -
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Re: Edexcel chemistry - unit 2 19th january 2012(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
wouldnt have known that if you wouldnt have said
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Re: Edexcel chemistry - unit 2 19th january 2012Another 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?Last edited by Cetacea; 14-01-2012 at 12:03. -
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Re: Edexcel chemistry - unit 2 19th january 20121. 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.(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?
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). -
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Re: Edexcel chemistry - unit 2 19th january 2012Great 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 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). -
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Re: Edexcel chemistry - unit 2 19th january 2012Give the balanced equation for the complete combustion of propanol.(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! -
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Re: Edexcel chemistry - unit 2 19th january 2012you 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.(Original post by aqua05)
Hiii can you explain to me this iodine bit reacting with alcohol
I dont seem to understand it.. thanks
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Re: Edexcel chemistry - unit 2 19th january 2012Electrophilic addition of alkenes.(Original post by 7even)
Hello, just wondering do we need to know any organic chemistry revolving around alkanes or alkenes whatsoever? -
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Re: Edexcel chemistry - unit 2 19th january 2012You can't say steamy white fumes...(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).
only say steamy fumes..
Steamy white fumes are only observed when it is mixed with ammonia -
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Re: Edexcel chemistry - unit 2 19th january 2012thanks(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.
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Re: Edexcel chemistry - unit 2 19th january 2012Nu-uh, white SMOKE is observed on the mouth of the test tube with ammonia. Steamy white fumes in the test tube is correct.(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
I forgive you. -
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Re: Edexcel chemistry - unit 2 19th january 2012C3H7OH + 41/2O2 --> 3CO2 + 4H2O(Original post by nutterfrutter)
give the balanced equation for the complete combustion of propanol.
One for you: write an equation for the thermal decomposition of sodium nitrate. -
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Re: Edexcel chemistry - unit 2 19th january 2012NaNO3 ---> NaNO2 + 1/2O2(Original post by Cetacea)
C3H7OH + 41/2O2 --> 3CO2 + 4H2O
One for you: write an equation for the thermal decomposition of sodium nitrate. -
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Re: Edexcel chemistry - unit 2 19th january 2012oh !(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.
sorry about that! -
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Re: Edexcel chemistry - unit 2 19th january 2012Break down of one reactant, using heat energy, to form more than one product.(Original post by cisne)
explain what is meant by the term thermal decomposition???? -
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Re: Edexcel chemistry - unit 2 19th january 2012but-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?
wouldnt have known that if you wouldnt have said 
