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Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: yasser37 on May 28, 2010, 12:45:38 pm

Title: Chemistry question
Post by: yasser37 on May 28, 2010, 12:45:38 pm: Hi guys

Nov. 02

Q. 4

Part e
Title: Re: Chemistry question
Post by: yasser37 on May 28, 2010, 12:48:30 pm: also Q.6 Part b ii
Title: Re: Chemistry question
Post by: nid404 on May 28, 2010, 04:27:54 pm: 4)e) H2O(l) + CO(NH2)2(aq) ? CO2(aq) + 2NH3(aq)
–287.0 + –320.5 –414.5 –81.0 X 2

Enthalpy of products= -414.5-(81X2)=-576.5kJ
Enthalpy of reactants= -287-320.5=-607.5 kJ
$\delta H= enthalpy of products-enthalpy of reactants$

= -576.5kJ- (-607.5)=+31 kJ/mol
Title: Re: Chemistry question
Post by: nid404 on May 28, 2010, 04:37:47 pm: 6)b) ii)

C₅H₁₁OH + NaBr------> C₅H₁₁Br+ NaOH

Molar Ratio of C₅H₁₁OH : C₅H₁₁Br is 1:1

Yield is 60%

15g of C₅H₁₁Br = 15/Mr moles Mr of bromopentane=151g
no of moles= 15/151 = 0.1 approx

since yield is 60%

60/100 X no of moles of C₅H₁₁OH = 0.1 moles of C₅H₁₁Br

no of moles of C₅H₁₁OH= 0.166 moles
Mr of C₅H₁₁OH= 88g
Mass of C₅H₁₁OH required= 0.166X 88=14.7 g
Title: Re: Chemistry question
Post by: unknown 101 on May 28, 2010, 09:11:53 pm: i wouldve helped you, but she answered faster!! ::) ;D
Title: Re: Chemistry question
Post by: moon on May 29, 2010, 01:25:09 am: can somebody help me to solve question no. 3 and Q1(c), (d), (e), (f) in ppr 52 Nov. 09.
thanx in advance.
Title: Re: Chemistry question
Post by: nid404 on May 29, 2010, 06:43:35 am: I'm doin AS...so p5 is greek to me
Title: Re: Chemistry question
Post by: moon on May 29, 2010, 09:48:14 am: ok thanx a lot.. :)