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# AS Chemistry- helping each other out! watch

1. (Original post by C0balt)
N has electronic configuration of 1s2 2s2 2p3 and in p orbital the three electrons are unpaired

Where can the increase in mass come from? Only chlorine. So calculate the number of moles of chlorine atoms (well they are ions but molar mass is the same anyway) in that compound
See the ratio of 0.1mol and the amount of chlorine and you will see

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Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question...
2. (Original post by gabby07)
Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question...
How..? Well it couldn't be anything else XD
Also the question was asked many times so I don't even remember how and when I first realised it haha

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3. Anyone doing AQA: What do we need to know for this point of the spec .. can't find anything in my notes

"know that early models of atomic structure predicted thatatoms and ions with noble gas electron arrangementsshould be stable"
4. (Original post by gabby07)
Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question...
its saying the INCREASE in mass, not what the final mass of the atoms and chlorine is combined. The INCREASE in mass after the two have REACTED is due to the ADDITION of Cl because that's the only thing that can cause the increase in mass because the ATOMS stay the SAME. so you do 7.1/35.5 = 0.2 moles of cl. ratio of atoms to Cl is: 1:2, so atom has to be +2!

I was also stuck on this Q, but I literally only JUST got it by reading your post!!

Thing i don't understand, is why you divide 7.1g by 35.5 and not by 71 since Cl2 is diatomic O.o maybe Cobalt can explain
5. (Original post by annie79)
its saying the INCREASE in mass, not what the final mass of the atoms and chlorine is combined. The INCREASE in mass after the two have REACTED is due to the ADDITION of Cl because that's the only thing that can cause the increase in mass because the ATOMS stay the SAME. so you do 7.1/35.5 = 0.2 moles of cl. ratio of atoms to Cl is: 1:2, so atom has to be +2!

I was also stuck on this Q, but I literally only JUST got it by reading your post!!

Thing i don't understand, is why you divide 7.1g by 35.5 and not by 71 since Cl2 is diatomic O.o maybe Cobalt can explain
Ahh, I see. I was also thinking the same as you about the diatomic nature of Cl but I just ignored it for the purposes of calculating the answer. I agree, it would be nice to know why it isn't Cl2?
6. Hi Can you please show me how to work out this question? its from Edexcel 2014 june

Oxygen gas, O2 , can be converted into ozone, O3 , by passing it through an electric discharge.

3O2 (g)=====>2O3 (g)

In an experiment, a volume of 300 cm3 of oxygen was used but only 10% of the oxygen was converted into ozone. All volumes were measured at the same temperature and pressure. The total volume of gas present at the end of the experiment, in cm3 , was

A 200

B 210

C 290

D 300

Thank you!!
7. (Original post by gabby07)
Ahh, I see. I was also thinking the same as you about the diatomic nature of Cl but I just ignored it for the purposes of calculating the answer. I agree, it would be nice to know why it isn't Cl2?
(Original post by annie79)
its saying the INCREASE in mass, not what the final mass of the atoms and chlorine is combined. The INCREASE in mass after the two have REACTED is due to the ADDITION of Cl because that's the only thing that can cause the increase in mass because the ATOMS stay the SAME. so you do 7.1/35.5 = 0.2 moles of cl. ratio of atoms to Cl is: 1:2, so atom has to be +2!

I was also stuck on this Q, but I literally only JUST got it by reading your post!!

Thing i don't understand, is why you divide 7.1g by 35.5 and not by 71 since Cl2 is diatomic O.o maybe Cobalt can explain
before you know the metal you don't know how many are going to be involved in the product I.e 1 for sodium, 4 for carbon... So you need to just divide by the mass of one chlorine atom which allows you to find the correct ratio
8. OCR B Salters
how did my fellow salters do on F333 (skills test)
9. (Original post by cilla_e)
Hi Can you please show me how to work out this question? its from Edexcel 2014 june

Oxygen gas, O2 , can be converted into ozone, O3 , by passing it through an electric discharge.

3O2 (g)=====>2O3 (g)

In an experiment, a volume of 300 cm3 of oxygen was used but only 10% of the oxygen was converted into ozone. All volumes were measured at the same temperature and pressure. The total volume of gas present at the end of the experiment, in cm3 , was

A 200

B 210

C 290

D 300
Thank you!!
The volume of each is directly proportional to the number of moles.

since 10% of the oxygen reacts => 30 cm3
(this leaves 270 cm3 unreacted)
3 moles of oxygen gives 2 moles of ozone
So (2/3)*30= 20 cm3

total volume of gas = 20+270=290 cm3 C

10. (Original post by VetVikki)
Anyone doing AQA: What do we need to know for this point of the spec .. can't find anything in my notes

"know that early models of atomic structure predicted thatatoms and ions with noble gas electron arrangementsshould be stable"
Theories of atoms basically:
first there was dalton's model (solid spheres), then thomson's model (plum pudding model)
then there was the gold foil experiment by ernest rutherford to show the plum pudding model was wrong and most of atom is just empty space (nuclear model)
then Bohr's model which showed why noble gases are inert,
then refined bohr's model
finally we have the quantum model
its quite detailed if you have a cgp guide or textbook you should probs check that ^^
and yes i am also on aqa by the way
11. Can anyone help with this
Attached Images

12. Yoo was wonderin if you guys could help me by explaining all the trends across and down groups, i think in unit 1 its like group 2,3,1,7? I struggle alot much help would be appreciated. could you also explain which elements deviate from the trend like mg with al and sulphur and phosphorus. Thanks

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13. (Original post by Mo_Jo.)
Can anyone help with this
you can use algebra but its way easier just thinking logically
10 is 20% 11 is 80% abundance
14. (Original post by gabby07)
Ahh, I see. I was also thinking the same as you about the diatomic nature of Cl but I just ignored it for the purposes of calculating the answer. I agree, it would be nice to know why it isn't Cl2?
(Original post by annie79)
its saying the INCREASE in mass, not what the final mass of the atoms and chlorine is combined. The INCREASE in mass after the two have REACTED is due to the ADDITION of Cl because that's the only thing that can cause the increase in mass because the ATOMS stay the SAME. so you do 7.1/35.5 = 0.2 moles of cl. ratio of atoms to Cl is: 1:2, so atom has to be +2!

I was also stuck on this Q, but I literally only JUST got it by reading your post!!

Thing i don't understand, is why you divide 7.1g by 35.5 and not by 71 since Cl2 is diatomic O.o maybe Cobalt can explain
When chlorine has reacted with something they are no longer a molecule

Dividing with 71 still works mathematically and in this case it was magnesium? So it would've be been easy, but if it were odd number group you would have a little bit of confusion

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15. (Original post by C0balt)
When chlorine has reacted with something they are no longer a molecule

Dividing with 71 still works mathematically and in this case it was magnesium? So it would've be been easy, but if it were odd number group you would have a little bit of confusion

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cool, makes sense!
16. (Original post by annie79)
cool, makes sense!
You're welcome...
17. (Original post by langlitz)
You're welcome...
i feel for you
18. (Original post by Azula)
Theories of atoms basically:
first there was dalton's model (solid spheres), then thomson's model (plum pudding model)
then there was the gold foil experiment by ernest rutherford to show the plum pudding model was wrong and most of atom is just empty space (nuclear model)
then Bohr's model which showed why noble gases are inert,
then refined bohr's model
finally we have the quantum model
its quite detailed if you have a cgp guide or textbook you should probs check that ^^
and yes i am also on aqa by the way
Thank you so much - CGP was my life at GCSE
19. Do we need to know about the theories? Not seen a question from any past exam papers asking about the theories
20. (Original post by VetVikki)
Thank you so much - CGP was my life at GCSE
same here!! And now i just use the cgp textbooks for biology and chemistry

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