Qualification > Sciences
chemistry CIE past ppr doubt
vanibharutham:
CH3SH + 3O2 ? CO2 + SO2 + 2H2O
A sample of 10 cm3 of methanethiol was exploded with 60 cm3 of oxygen.
The first task is to find the limiting reagent...
Calculate the number of moles of CH3SH
n = 10/240000 = 0.00041666666667
Calculate number of moles of O2
n = 60/ 24000 = 0.0025
divide by three to get in correct ratio:
0.0008333333
And from this you can see that the oxygen gas was added in excess and so methanethiol was the limiting reagent.
From the equation we know that three moles of oxygen react with one mole of methanethiol...
If we multiply the number of moles of methanethiol by 3, we get 0.00125 moles... this is the number of moles of oxygen that actually reacted...
therefore,
0.00125 moles = 30 cm³
only 30 cm³ of the 60cm³ reacted....
means that 30 was left over...
TOTAL VOLUME OF REMAINING GASES:
10cm³ of carbon dioxide was produced
10cm³ of sulphur dioxide was produced
30cm³ of oxygen was left unreacted...
Hence the answer is
50cm³
C
sweetie:
thank u sooo much :-*
sweetie:
hey ppl,
in da may06 paper1 Q36
why is ammonia not a reducing agent??????
and also Q32 of da same year is a bit difficult
thanx in advance 4 any help...
Saladin:
Question 36
The answer is B. That is both statements 1 and 2 are correct.
1 is true because Cl2 which has an oxidation state of 0, becomes Cl-. Thus as reduction is gain of electrons, chlorine is reduced by Ammonia.
2 is true because NH3 becomes NH4+. It gains a hydrogen ion i.e. a proton. As we know bases are proton acceptors.
Question 32
The answer is B. That is both statements 1 and 2 are correct.
1 is true because you need to isolate an atom of sodium, before you can ionize it, i.e. by removing an electron.
2 is true because, in order for an atom of sodium to gain a charge you need to ionize it. As it has only a charge of 1+, you only take into account the first ionization energy.
sweetie:
Thank You sooooooo much
;)
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