Chemistry: Post your doubts here!

[Gémeaux]

cud anyone post here sum link fr lectures on carbonyl componds???? plzzzzzz =(

 

[sweetiepie]

http://web.pdx.edu/~wamserc/C335W00/15notes.htm

check out this

 

[Gémeaux]

thankuu

 

[sweetiepie]

welcum anything esle post here or pm me

 

[NehaKush]

hi.. i need help in paper5.. i don't know how to do those question

 

[yubakkk]

can any one make me clear on sn1 and sn2??

 

[yubakkk]

chemistry 33 is near so HELP HERE

http://www.xtremepapers.com/CIE/Interna ... _qp_31.pdf
i need help of titration q 1 c
any one please??

 

[hassam]

WHY IS E(cell) = E(right)-E(left)???

see QUESTION 1 http://www.xtremepapers.com/CIE/Interna ... 3_qp_4.pdf
if we use E(CELL)=E(+ve)-E(-VE ELECTRODE) correct ans will not cum .....!!!!

 

[karishma92]

1 You are provided with the following.
FB 1, 3.00 mol dm–3 hydrochloric acid, HCl
Three tubes containing different mixtures of sodium carbonate, Na2CO3, and sodium
hydrogencarbonate, NaHCO3, each with a total mass of 5.00 g of mixture.
tube labelled mass of Na2CO3 / g mass of NaHCO3 / g % by mass of Na2CO3
FB 2 1.00 4.00 20.0
FB 3 2.50 2.50 50.0
FB 4 4.00 1.00 80.0
You are to determine the temperature change, ΔT, when the contents of each of the tubes FB 2,
FB 3 and FB 4 react with an excess of hydrochloric acid, FB 1.

(a) (i) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
of sodium carbonate, Na2CO3. Show your working.
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
[Mr: Na2CO3, 106.0]

(ii) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
of sodium hydrogencarbonate, NaHCO3. Show your working.
NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
[Mr: NaHCO3, 84.0]

pleaseeee HELP...

 

[waleed10]

tell me something about chem 33 tomo

 

[yubakkk]

1 You are provided with the following.
FB 1, 3.00 mol dm–3 hydrochloric acid, HCl
Three tubes containing different mixtures of sodium carbonate, Na2CO3, and sodium
hydrogencarbonate, NaHCO3, each with a total mass of 5.00 g of mixture.
tube labelled mass of Na2CO3 / g mass of NaHCO3 / g % by mass of Na2CO3
FB 2 1.00 4.00 20.0
FB 3 2.50 2.50 50.0
FB 4 4.00 1.00 80.0
You are to determine the temperature change, ΔT, when the contents of each of the tubes FB 2,
FB 3 and FB 4 react with an excess of hydrochloric acid, FB 1.

(a) (i) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
of sodium carbonate, Na2CO3. Show your working.
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
[Mr: Na2CO3, 106.0]

(ii) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
of sodium hydrogencarbonate, NaHCO3. Show your working.
NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
[Mr: NaHCO3, 84.0]

pleaseeee HELP...

mole of hcl=2*mole of na2co3
v of hcl= 2*(5\(106*3)
=31.45 cm^3


in ii
maole of hcl = mole of nahco3
v=7.5\(84*3)
= 19.84

 

[abcd888]

help in chemistry questions...

1. Hydrogen bonding can occur between molecules of methanol, HCHO, and molecules of liquid Y. What could liquid Y be? A. CH3OH B. CH3CHO, C. CH3COCH3 D. CH3CO2CH3

2. which solid exhibits more than one kind of chemical bonding? A. brass B. copper. C.diamond D. metallic

3. which compound has boiling pint which is influenced by hydrogen bonding? A. CH3CHO B. CH3OCH3 C. HCO2H D. HCO2CH3

4. Describe the bonding present in: Solid Krypton Kr and Solid Rubidium Rb

5. HCN reacts with ethanol, CH3CHO. Give the displayed formula of the organic product formed. and what type of reaction is this?

Please also explain

 

[XPFMember]

WHY IS E(cell) = E(right)-E(left)???

see QUESTION 1 http://www.xtremepapers.com/CIE/Interna ... 3_qp_4.pdf
if we use E(CELL)=E(+ve)-E(-VE ELECTRODE) correct ans will not cum .....!!!!

Assalamoalaikum!!

You are probably, doing some mistake!
E(CELL)=E(+ve)-E(-VE ELECTRODE)

0.76 = 0.34 - E(-ve)

E(-ve) = 0.34 - 0.76
= -0.42 V

 

[kewaldoshi]

can someone please post all the formulas needed for stoichiometery

 

[sweetiepie]

http://www.chemtutor.com/mols.htm
http://www.sparknotes.com/chemistry/sto ... ion2.rhtml

i hope this may help u

 

[AkhlaqAhmed]

there's a doubt in the chem paper 31 m/j 2011 q1 c (iii)....ER says that we're supposed to use our answer from c(ii) instead of using the approximate conc. given above.....how do we calculate using the answer in c(ii)???????.......plzzzzz REPLY FAST since i have my chem practical exam today at 12pm!!!!!!!!!!!

 

[vaishster]

i wrote enthapy of neutr as 58.1.. (i think it ws 57).. will i get mark ??

 

[nikhilthomas]

the ans has to in 57 so u won't get mark

 

[AkhlaqAhmed]

Firstly, if you had paper 33 then this is for you, and secondly, if you didn't get the right answer you will get marks for the formula that you used (which should be the multiplication between 4.3J, temperature change and the volume that you got at the point of intersection in the graph)

 

[rahulsharma]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

u must see which is more positive E value. For this case the Chromate is more +ve...it shud be written the same way..that is no inverse. The Cl- equation should be reverse as it less +ve!

Hope tht helps