Chemistry Help HERE ONLY !!

[asus]

u guys...help me with this question..
ppr3 june 04 7 b) ii

[heat619]

Is the pressure for the Contact Process 10 atm or 20 atm, cuz the mark scheme says 10 but the book says 20 :S

huh we learnt it was 1 atp not 10 or 20 n i checked wikipedia too they say its 1-2 atp so the rite answer is 1 atmospheric pressure

so its under normal pressure?

[nid404]

@shogun. CaCO3= 40+12+16+16+16= 100
Number of moles of CaCO3 = 0.3/100= 0.003
Number of moles of HCL = 1 mol per dm3, and 1000cm3 = 1 dm3. 5/1000= 0.005
The reaction needs 1 mol of CaCO3 and 2 mols of HCl. So the HCl needs to be double the the CaCO3, but here there isnt enough, because the CaCO3 is 0.003, and the HCl needs to be 0.006, but its only 0.005. So CaCO3 is in excess.

I was kinda confused myself doing the question. Check with the mark scheme and tell me if im correct. If i am, +rep me PLZ. I REALLY NEED IT!!

ur right and i +repped u in the morning..it was -8.....there's sumthin wrong...but ill do it again

[Ibiza279]

@shogun. CaCO3= 40+12+16+16+16= 100
Number of moles of CaCO3 = 0.3/100= 0.003
Number of moles of HCL = 1 mol per dm3, and 1000cm3 = 1 dm3. 5/1000= 0.005
The reaction needs 1 mol of CaCO3 and 2 mols of HCl. So the HCl needs to be double the the CaCO3, but here there isnt enough, because the CaCO3 is 0.003, and the HCl needs to be 0.006, but its only 0.005. So CaCO3 is in excess.

I was kinda confused myself doing the question. Check with the mark scheme and tell me if im correct. If i am, +rep me PLZ. I REALLY NEED IT!!

listen to check the mole ratio u dn need to check the moles in the chemical equation.

n as u get the answer 0.005 which is greater than 0.003 HCl is in excess believe me

n to get the volume of CO2 u gotta give me the complete balanced chemical equation  first.

n yh heat619 its under normal pressure

[effigs]

here it is

(ii)one piece of marble 0.3g, was added to 5cm³ of hydrochloric acid, concentration 1.00 mol/dm³. which reagent is in excess? give reason for your answer.

mass of one mole of CaCO₃ =100g

number of moles of CaCO₃= .................................................................
number of moles of HCl=.......................................................
regent in excess is ...........................................................
reason....................................................................
                                                                                                   [4]

(iii) use your answer to (ii) to calculate the maximum volume of carbon dioxide produced measured at r.t.p.
...[1]

explain to me what u have to do, plz dont just give me the answer, do explain every part on how to find the excess.

Thanks

number of moles of CaCO₃= 0.003 (because mass of calcium carbonate over molecular mass of calcium carbonate = 0.003)
number of moles of HCl = 0.005 (because number of moles= volume (in dm³) x concentration =0.005)
reagent in excess= CaCO₃
reason= beacuse as the mole ratio (in the equation on the previous page) is 1:2:1:1:1, the reaction would require HCl of two times the moles of CaCO₃ (i.e 0.003 x 2 = 0.006) and since we have 0.005 moles of HCl which is lesser than required, CaCO₃ is in excess [make sense??]

max. volume of carbon dioxide produced= 0.06 (because as we have 0.005 moles of HCl we have to work with it to find the number of moles of CO₂ (mole ratio) and then times it by 24 [as per the formula] to get the answer)
 
well hope that helped...

[islu_jf]

CAn u plz guys tel me what the hell does the "catalytic converter" do??
plz tel me evrythng abt it..
I really need help

[goin4dakill]

Hey Guys!
Im just new to the forum and I really dont understand how it works! I know you have better things to do and everyone is preparing for chemistry tommorow! But how do u '+rep' someone..and why do you do it? Where are you guys from? We obviosly wont be doing the exam at the same time..but I shall be doing it in approx 13 hours and 15 minutes. I live in Greece So do people actually tell others what theyve done in the exam? Sorry, i know..really general..dont answer if u think its irrelevent.
Thanks and best of luck for the exam tomoz!

[heat619]

CAn u plz guys tel me what the hell does the "catalytic converter" do??
plz tel me evrythng abt it..
I really need help

A catalytic converter is fitted into the exhaust of cars to reduce pollution.
How does it do that?
Well cars emit CO due to incomplete combustion of fuel in the engine,which is harmful, and NO, the catalytic converter does the following reaction,
CO+NO --> Co2 + N2
so the gases become harmless.

+rep if correct

[nid404]

People i have found this site .....Hope its useful..... http://www.chemactive.com/grade_10.html 

hey thanks +rep.... ur first

@ibiza a little needs to be corrected with the catalytic converter. it converts carbon monoxide to carbon dioxide and oxides of nitrogen to nitrogen(not nitrogen dioxide)

[Shogun]

Thanks all of u... its correct effigs and thukon , ill +rep u all and nid too

thanx all rep u all 2morow cuz site too slow!

[islu_jf]

People i have found this site .....Hope its useful..... http://www.chemactive.com/grade_10.html 

hey thanks +rep.... ur first

@ibiza a little needs to be corrected with the catalytic converter. it converts carbon monoxide to carbon dioxide and oxides of nitrogen to nitrogen(not nitrogen dioxide)

Ok look u dnt get.. do u like heat it with excess oxygen so it can turn from CO to CO2??

[kam]

u guys...help me with this question..
ppr3 june 04 7 b) ii

can someone answer tht
i need help with that too

[Ibiza279]

actually its CO -> CO2 and nitrogen oxides -> nitrogen and oxygen

[nid404]

People i have found this site .....Hope its useful..... http://www.chemactive.com/grade_10.html 

hey thanks +rep.... ur first

@ibiza a little needs to be corrected with the catalytic converter. it converts carbon monoxide to carbon dioxide and oxides of nitrogen to nitrogen(not nitrogen dioxide)

Ok look u dnt get.. do u like heat it with excess oxygen so it can turn from CO to CO2??

oh dear no....
this is the reaction taking place in the converter

2CO+2NO--->2CO₂+N₂
or
4CO+2NO₂--->4CO₂+N₂

[Ibiza279]

we dn care if it burns it or does smething naughty with it v jus knw it that thats what happens n its gna get us the mark
n yh sorry bout the catalytic converter everybody was busy watchn top gear videos thgh tmrws the exam well am off now tk everyone all the best !