Chemistry p5

[Rommarrooo]

could someone help me with the answers to the table in Q2, october november 2010, variant 53. i dont know if mine are correct or not, dont think so though. PLEASE

 

[gary221]

could someone help me with the answers to the table in Q2, october november 2010, variant 53. i dont know if mine are correct or not, dont think so though. PLEASE

first write down the stoichiometric quation
HO2CCH2CH2CO2H + 2NaOH ----> 1 mole of succinic acid combines wth 2 moles of NaOH (knowing the products is not imp) ratio = 1 : 2
Now, find the no. of moles of NaOH in water ie concentration = moles/volume(in dm^3)
So, no of moles of NaOH = 0.1 * (24.3/1000)
moles of NaOH = 2.43 * 10^-3
So, moles of succinic acid (in waster) = (2.43 * 10^-3)/2 -----> 1.215 * 10^-3

Now, v just have to find the concentration (volume of water is given)
So, conc = moles/vol
conc = (1.215 * 10^-3)/ (10 * 10^-3)
conc = 0.1215 mol dm^-3

the same for the others...
hope u gt it!!

 

[Rommarrooo]

Oh i sort of did this, but how were you supposed to know that you had to make a stoichiometric equation, especially as you didnt know the products? How could you balance the molar ratios?

 

[Rommarrooo]

Also thankyou very much!

 

[gary221]

succinic acid = has 2 -COOH grps.
thts why

 

[knowitall10]

succinic acid = has 2 -COOH grps.
thts why

Wow, we've undergone this huge discussion on this question in Chem Post your doubts thread
Phew! That was hell loads of work for me!
Btw, can anyone please tell me what the inert pair effect is?

 

[mujtabashahnawaz]

Can someone help me with nov 09/51 Q1(d)

 

[mujtabashahnawaz]

Can someone also help with june 10/52 Q1(d)

 

[raamish]

hey guys in j11/52 in qs 1c in the markscheme there is written that to achieve temperature mark using a water bath in 1d equilibration must be stated. What does this mean?? help plzzz

 

[xhizors]

Can someone help me with nov 09/51 Q1(d)

Voila its Easy
First react Na Thio bro with Potassium Sulfate to get Iodide Ions with a 20cm3 each
then pour persulfate to them after adding starch and start stop watch and stop it until blue color appears

take care of capacity of apparatus like 250 cm3 conical flask, 100cm3 measuring cylinder

For changing Concentrations
add 30cm3 of persulfate in measuring cylinder and 10 cm3 of distilled water and so on to get a decreased concentrated solution by decreasing conc u get complex more later hence rate decreases!!
hope it helps 1!

 

[raamish]

Voila its Easy
First react Na Thio bro with Potassium Sulfate to get Iodide Ions with a 20cm3 each
then pour persulfate to them after adding starch and start stop watch and stop it until blue color appears

take care of capacity of apparatus like 250 cm3 conical flask, 100cm3 measuring cylinder

For changing Concentrations
add 30cm3 of persulfate in measuring cylinder and 10 cm3 of distilled water and so on to get a decreased concentrated solution by decreasing conc u get complex more later hence rate decreases!!
hope it helps 1!

hey can u answer my question as well on equilibration?

 

[xhizors]

hey can u answer my question as well on equilibration?

why not!
you immeresed thermometer in water bath to observe or measure the temperature, as sulfur is being produced in reaction vessel(ur apparatus i guess) which is going to opaque the system so u cant measure it and it is stated u have to measure it accurately

for this:
However, in (d)in order
to access the ‘temperature’ mark using such a water-bath
‘equilibration’ must be stated or clearly implied.)

it means if u haven't stated so in diagram(measuring temp) so in d their must be written something which shows the measuring of constant temp