Chemistry Doubts: IGCSE Paper 3

[ZainH]

Do we need to know the tests for cations and anions? Or was that just for p6?

 

[Abu mota]

sometimes they ask for it but rarely and if u studied them before then they are going to be easy

 

[aliqamar1995]

Well first for yield you take out the number of moles according to the given values, you can use the formulas for moles, then you do the ratio method and find the number of moles of the other product now once you have that ! calculate the relative molecular mass of the product and multiply that by number of moles and you get the theoretical yield ! actual yield/theoretical yield x 100 = answer
Hope you get it

 

[owais rafiq]

explain the procedure for titration,neutralisation and precipitation?? :S

 

[aliqamar1995]

Do we need to know the tests for cations and anions? Or was that just for p6?

No actually you have to you never know ! just go through it once !

 

[ZainH]

All right thanks guys!

 

[aliqamar1995]

Q7. Part c, iii, how the hell are they dividing 1000/20 :/ Please help guys! http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_3.pdf

 

[Mozmozil]

explain the procedure for titration,neutralisation and precipitation?? :S

Titration is a method to prepare soluble salts , you only use it for group 1 and ammonium salts,, , precipitation is used to make insoluble salts ,, i think you mean by neutralisation (excess solid method ?) if yes then its used to make soluble salts you can use it only for transition metals salts .

 

[Mozmozil]

Q7. Part c, iii, how the hell are they dividing 1000/20 :/ Please help guys! http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_3.pdf

ok for concentration = moles/volume ,,, we have calculated the number of moles in par c)ii to be 0.005 moles,,, and now we want to find the concentration of oxalic acid
read the question carefully it gave u the volume of aqueous oxalic acid which was y 20.0 cm3 ,,, u need to convert the volume 20.0 cm3 to dm3 by dividing it by 1000 which is 0.02dm3. Thats it subsitute into formula.
0.005/0.02= 0.25 , mol /dm3

 

[Lujain M.]

guys I dont understand equilibrium ...i know the effect of inc and dec. but i dont know how do i know which is forward or backward..:S

 

[salmanhassan]

what r the possiblities of topic coming in chem paper 3 contact processi s coming for sure any else?

 

[Mozmozil]

guys I dont understand equilibrium ...i know the effect of inc and dec. but i dont know how do i know which is forward or backward..:S

its like a seesaw,,, imaging the chubby guy as the reactants ,, and the thin one as the products ,,, if the concentration of the reactant increased we will not get an equilibrium,,so the reactants needs to be shifted to the right to achieve equilibrium ,,,, same thing for products,, if the concentration of products increase ,, then seesaw will be turned so to achieve equilibrium the products needs to be shifted to the left .

 

[Lujain M.]

omg! thankk youu! I was confused...but it's okay now!
GOOD LUCK FOR TMRW

 

[Nimaay]

what time is the exam??????
mine is in 3 hrs

 

[MERIHAN]

i) Describe the chemistry of making butanol from petroleum by the following route.
petroleum → butene → butanol
plz answer !!! thanks in advance
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_31.pdf ( q no 6 a (1) )

 

[Dudu]

Somebody help!?

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_32.pdf
Q8) C)

A 5.00g sample of impure lead(II) nitrate was heated. The volume of oxygen formed was0.16 dm3measured at r.t.p. The impurities did not decompose.Calculate the percentage of lead(II) nitrate in the sample.2Pb(NO3)2→ 2PbO + 4NO2+ O2

Number of moles of O2 formed = .......................................
Number of moles of Pb(NO3)2 in the sample = .......................................
Mass of one mole of Pb(NO3)2= 331 g
mass of lead(II) nitrate in the sample = ....................................... g
Percentage of lead(II) nitrate in sample = .....................................

 

[Abu mota]

i) Describe the chemistry of making butanol from petroleum by the following route.
petroleum → butene → butanol
plz answer !!! thanks in advance
http://www.xtremepapers.com/papers/CIIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_31.pdf ( q no 6 a (1) )

hi, as you know petroleum is extracted using fractional distillation and then u will get large unuseful Alkane which can be broken down to butene by catalytic cracking then add steam at 60 ATM and 300 degrees and phosphoric v catalyst. I hope I helped

 

[MERIHAN]

hi, as you know petroleum is extracted using fractional distillation and then u will get large unuseful Alkane which can be broken down to butene by catalytic cracking then add steam at 60 ATM and 300 degrees and phosphoric v catalyst. I hope I helped

thank you sooo much !!!! may allah succeed you in achieving your dreams !!! ameen

 

[Abu mota]

Somebody help!?

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_32.pdf
Q8) C)

A 5.00g sample of impure lead(II) nitrate was heated. The volume of oxygen formed was0.16 dm3measured at r.t.p. The impurities did not decompose.Calculate the percentage of lead(II) nitrate in the sample.2Pb(NO3)2→ 2PbO + 4NO2+ O2

Number of moles of O2 formed = .......................................
Number of moles of Pb(NO3)2 in the sample = .......................................
Mass of one mole of Pb(NO3)2= 331 g
mass of lead(II) nitrate in the sample = ....................................... g
Percentage of lead(II) nitrate in sample = .....................................

Hi,
mol= vol/24 and so 0.16/24=6.6667x 10^-3 mols
then they are in the ratio 1:2 so multiply the mol of oxygen by 2 to give u 0.0133 mols
then mass=molxMr and so 331x0.0133= 4.41 g
then 4.41/5 x 100=88.2%

I hope i helped

 

[rjcooo1]

BEST OF LUCK EVERYBODY