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Chemistry: Post your doubts here!

KurayamiKimmi

KurayamiKimmi

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user said:
Assalamoalaikum wr wb!​
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need help, plz... ...:unsure:​
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P.S. I'm reposting them :D​
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9701-j-05-q-6-jpg.8598
Click to expand...
S has poor conducitivity when solid but conducts well in liquid state=must bean ionic compound
S has a mp of2800--this shows us that it has to MgO because in the course we are given the estimate mp of MgO (2000C)
T has a good conductivty in the solid state-so :
it cant be Sio2 or diamond -neither conduct electricity
options left =Cu or graphite -liquid conductivity is not known -Cu conducts in the liquid state too .so it has to be graphite
 
KurayamiKimmi

KurayamiKimmi

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Casablanca said:
Could you check if the answer to 12 is C? If so, I could help. And if it's B, I still know how it works, but I think it's C.

(I thought since you helped me so much, I could try and help you out with this one. :p I tried doing 21, and I know how to do it usually, but my answer is wrong, so I don't think I'd be of much help with that one...)
Click to expand...
thanks ^^ yes its C ..so how do you do it ?
 
gary221

gary221

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KurayamiKimmi said:
help....anyone?:cry:
Click to expand...
For 10, Kc = 4. Initial conc : ethanol = 1 mol Ethanoic acid = 1 mol Ethyl ethanoate = 0 mol Water = 0 mol
Final conc : Ethanol =(1-x)mol Ethanoic acid=(1-x)mol Ethyl ethanoate = x mol Water = x mol
Kc = 4 = [x] [x] /[1-x] [1-x]
4 = x^2/(1-x)^2
4- 8x+3x^2 = 0
Solve by quadratic eqn to gt d ans..
Hope i helped...;)
 
KurayamiKimmi

KurayamiKimmi

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gary221 said:
For 10, Kc = 4. Initial conc : ethanol = 1 mol Ethanoic acid = 1 mol Ethyl ethanoate = 0 mol Water = 0 mol
Final conc : Ethanol =(1-x)mol Ethanoic acid=(1-x)mol Ethyl ethanoate = x mol Water = x mol
Kc = 4 = [x] [x] /[1-x] [1-x]
4 = x^2/(1-x)^2
4- 8x+3x^2 = 0
Solve by quadratic eqn to gt d ans..
Hope i helped...;)
Click to expand...
yes you did (y) ^_^ thanks a lot
 
J

jsg

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help needed in Q 9 and 3
 

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iKhaled

iKhaled

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guys i have found a mistake in the mark scheme of may june 11 paper 11 Oo

question 37, the answer is B? how come and an ammonium ion only has 8 electrons :S:S:S:S:S
 
G

geek101

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iKhaled said:
guys i have found a mistake in the mark scheme of may june 11 paper 11 Oo

question 37, the answer is B? how come and an ammonium ion only has 8 electrons :S:S:S:S:S
Click to expand...


option 1 says 10 which is true, 8 in the outer shell of bonded N and two in the inner shell, cuz N= 2, 5. so 1 is right
 
P

Paparazzi478

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11 0.144 g of an aluminium compound X react with an excess of water, to produce a gas. This gas
burns completely in O2 to form H2O and 72 cm3 of CO2 only. The volume of CO2 was measured at
room temperature and pressure.
What could be the formula of X?
[C = 12.0, Al = 27.0; 1 mole of any gas occupies 24 dm3 at room temperature and pressure]
A Al 2C3 B Al 3C4 C Al 4C3 D Al 5C3

Can anyone tell me how the answer is C
thankyou
 
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