• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Chem p22

Messages
222
Reaction score
25
Points
38
LOL :p you actually calculated the MOLES OF H2 gas :) the volume of H2 gas was given :) so you had to change it into number of moles of atoms of H :) only this way did the ratio of alchol and H atoms came 1:2 meaning two H atoms were realsed per one mole of that compund meaning that each mole had two OH groups so two H atoms were liberated :)

I know... I already multiplied it by two in the above post for number of moles of ATOMS
 
Messages
63
Reaction score
19
Points
18
I know... I already multiplied it by two in the above post for number of moles of ATOMS
i got confused by all the standard forms i kept my answers in fractions na :p bus phir tu relax and wait for your A to come :p if the rest of your paper also went great :D
 
Messages
168
Reaction score
43
Points
38
guys what are your thoughts on this for the aluminium burning in chlorine question i wrote the equation as 2AL(s) + 3Cl2(g) ---> Al2Cl6(g) is the examiner gona allow this?
 
Messages
63
Reaction score
19
Points
18
... Allahu Akbar...

Show me that guide. o_o
Hodder Education is the publisher .... David Bevan the author it is endorsed by CIE and it is the official guide for A and AS level :) i cant upload pics but am sure you can get it from somewhere and see it for yourself :) but let me assure you that is the correct answer :) or just look it up on net :p
 
Messages
224
Reaction score
183
Points
53
By the way guys, that Enthalpy Change was -129. I remembered the whole question, so I confirmed it with my Chem sir, and even with the textbook... I drew the Hess Cycle correctly according to the book, and then resolved the question, and still got -129 as the answer. My Sir confirmed it that the reaction was supposed to be exothermic... Al-Hamdulillah (y)
 
Messages
168
Reaction score
43
Points
38
By the way guys, that Enthalpy Change was -129. I remembered the whole question, so I confirmed it with my Chem sir, and even with the textbook... I drew the Hess Cycle correctly according to the book, and then resolved the question, and still got -129 as the answer. My Sir confirmed it that the reaction was supposed to be exothermic... Al-Hamdulillah (y)
Hey can u do me a favour and confirm one more thing with ur sir. Ask him that for the part in which we had to give the effect of conditons on rate of formation of methanol i wrote for temp that. = The temperature provided is low and so the r.o.f will be less bcz average kinectic energy of molecules decrease and less effective collision occurs. The temp is considered low becz for normal commercial processes the temp used is around 750K and since rx is exo low temp is preferd :D plz man confirm this :D
 
Messages
110
Reaction score
98
Points
38
Made lots of mistakes so my paper is full of crosses and sorries but got the answers correct finally except the ph of solution formed when chlorides of si and al are dissolved.
 
Messages
110
Reaction score
98
Points
38
By the way guys, that Enthalpy Change was -129. I remembered the whole question, so I confirmed it with my Chem sir, and even with the textbook... I drew the Hess Cycle correctly according to the book, and then resolved the question, and still got -129 as the answer. My Sir confirmed it that the reaction was supposed to be exothermic... Al-Hamdulillah (y)
Yep, it should be. Many mistaked the enthalpy change of combustion for the enthalpy change of formation and the answer came positive.
 
Messages
110
Reaction score
98
Points
38
Hey can u do me a favour and confirm one more thing with ur sir. Ask him that for the part in which we had to give the effect of conditons on rate of formation of methanol i wrote for temp that. = The temperature provided is low and so the r.o.f will be less bcz average kinectic energy of molecules decrease and less effective collision occurs. The temp is considered low becz for normal commercial processes the temp used is around 750K and since rx is exo low temp is preferd :D plz man confirm this :D
Nope, the answer is:
a temperature of 600k is a compromise temperature because an increase in temperature would not be favourable for an exothermic reaction, but a low temperature would provide insufficient energy to reactant molecules for effective collisions.
(Mix it up, shorten it up, but the answer's there)
 
Messages
52
Reaction score
6
Points
18
Nope, the answer is:
a temperature of 600k is a compromise temperature because an increase in temperature would not be favourable for an exothermic reaction, but a low temperature would provide insufficient energy to reactant molecules for effective collisions.
(Mix it up, shorten it up, but the answer's there)

Sorry to say but your answer is wrong most probably (God knows best).
You see, there was no equilibrium sign (was there? I don't think so)
And they SPECIFICALLY asked for the effect of the conditions on THE RATE OF REACTION. NOT the yield.
Even if they wanted the yield, temperature would not effect the yield because there was no equilibrium sign - for a one way reaction, temperature does not effect yield so no need for compromise.
 
Messages
52
Reaction score
6
Points
18
My paper went good Alhamdulillah.
But I made some REALLY silly mistakes!.
Like, the reaction for Aluminium and Chlorine, in question 1,

I accidentally gave the reaction for Aluminium Oxide and Chlorine because I wasn't paying attention :S.. I know its so stupid!
The other answers before the question were alright, but this mistake was so stupid, do you think the examiner might get angry and deduct marks for the previous question as well ? Are the examiners allowed to do that ?:p Because the previous question was the observation for the reaction. Do you think they will cut that mark too because my reaction was wrong?

I made another silly mistake witht he reaction of Methanol and Oxygen. I gave Methanol as a gas! I was not paying attention at all.​
 
Messages
110
Reaction score
98
Points
38
My paper went good Alhamdulillah.
But I made some REALLY silly mistakes!.
Like, the reaction for Aluminium and Chlorine, in question 1,

I accidentally gave the reaction for Aluminium Oxide and Chlorine because I wasn't paying attention :S.. I know its so stupid!
The other answers before the question were alright, but this mistake was so stupid, do you think the examiner might get angry and deduct marks for the previous question as well ? Are the examiners allowed to do that ?:p Because the previous question was the observation for the reaction. Do you think they will cut that mark too because my reaction was wrong?

I made another silly mistake witht he reaction of Methanol and Oxygen. I gave Methanol as a gas! I was not paying attention at all.
No, the marking scheme usually says 'allow ecf for wrong answer in the previous question' so you will gain marks if your answer is correct, even when it depends on the wrong answer you formerly calculated, or wrote, for that matter.
And I think methanol was given as gas in the question itself.
The question about methanol was not about equilibrium, but the answers were similar to that of an equilibrium question, and you just couldn't mention equilitbrium anywhre or youd lose marks.
 
Messages
110
Reaction score
98
Points
38
Sorry to say but your answer is wrong most probably (God knows best).
You see, there was no equilibrium sign (was there? I don't think so)
And they SPECIFICALLY asked for the effect of the conditions on THE RATE OF REACTION. NOT the yield.
Even if they wanted the yield, temperature would not effect the yield because there was no equilibrium sign - for a one way reaction, temperature does not effect yield so no need for compromise.
I did not say anything about equilibrium. Mentioning the word equilibrium would have cost anyone the whole question itself. But i said that number of effective collisions would increase, and hence the rate of reaction, and probably the yield too, for that matter, but its not totally wrong as you indicate.
This question was similar to an equilibrium question, you just couldn't mention equilibrium anywhere.
 
Messages
168
Reaction score
43
Points
38
Nope, the answer is:
a temperature of 600k is a compromise temperature because an increase in temperature would not be favourable for an exothermic reaction, but a low temperature would provide insufficient energy to reactant molecules for effective collisions.
(Mix it up, shorten it up, but the answer's there)
Man they specifically said that use the condition/something to answer. It wasn't the equilibrium one and what i meant was temp is directly propotional to R.O.F i just said low temp so less rate. I want u to confirm is that will he give me marks caz most people wrote the same but high temp. high R.O.F i wrote LOW tmep Low R.O.F sense is the same in both :p
 
Messages
110
Reaction score
98
Points
38
Man they specifically said that use the condition/something to answer. It wasn't the equilibrium one and what i meant was temp is directly propotional to R.O.F i just said low temp so less rate. I want u to confirm is that will he give me marks caz most people wrote the same but high temp. high R.O.F i wrote LOW tmep Low R.O.F sense is the same in both :p
I guess that's right.
 
Messages
719
Reaction score
2,644
Points
253
It was burning in Chlorine. Its not confirmed that Sulfur burns in a blue flame in Chlorine, I'm 90% sure that Sulfur burns in a yellow flame in a chlorine atmosphere; producing a dark yellow liquid (S2Cl2).

Sodium was more correct, and safer.

I screwed up this question big time. I lost like at least 2 marks here just because of sheer stupidity, even though I knew the correct answers. :cry: I wrote 'Light yellow flame' for Aluminum's reaction in Chlorine, even though I could have written 'yellow color fades' (I had that in my mind then) as I wasn't sure of Aluminum's flame color - but I didn't. :( I made up something entirely new 'light yellow flame'.

Bleh.

Anyways, the correct observations were; white sparks, white solid produced, or yellow color of gas disappears.

Then I turned Aluminum chloride's reaction with water as Basic. >_< I wrote it as Acidic (ph 3), then I crossed it and wrote pH8. >_< How idiotic of me.

Question 1: The table in which the reactions of chlorides with water were asked;- was it worth 3 marks or 6?

Question 2: When writing the pH of SiCl4's reaction with water, I wrote 3-4. In the Book it says 2. Will mine be accepted or not?

Question 3: What was the enthalpy change of formation of Methanol? I got -129 kJ mol-1.

Question 4: How do we know that, one of those organic compounds we were told to draw the structure of; that contained 2 Alcohol groups?

Question 5: What was the empirical formula they asked us to calculate? I got C6H8O7 or something...
But sodium burns with white flame. In the field of science white is not regarded as a color

Q1: 6 marks
Q2: Accepted i think
Q3:-129
Q4:Calculate the molar ratio between compound in the reaction
Q5:C6H8O7
 
Top