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Chemistry: Post your doubts here!

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Tasneem_m98

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Please help O/N/14 paper 13

8 Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute sulfuric acid to produce a mixture of FeSO4 and Cr2(SO4)3. The FeSO4 reacts with K2Cr2O7 in acid solution according to the following equation. 14H+ + 6Fe2+ + Cr2O72– → 2Cr3+ + 6Fe3+ + 7H2O When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid, and the resulting solution titrated, 13.1 cm3 of 0.100 mol dm–3 K2Cr2O7 is required for complete reaction. What is the percentage by mass of Fe in the sample of ferrochrome? A 1.22 B 4.39 C 12.2 D 43.9
 
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Tasneem_m98

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Please help O/N/14 paper 13

8 Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute sulfuric acid to produce a mixture of FeSO4 and Cr2(SO4)3. The FeSO4 reacts with K2Cr2O7 in acid solution according to the following equation. 14H+ + 6Fe2+ + Cr2O72– → 2Cr3+ + 6Fe3+ + 7H2O When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid, and the resulting solution titrated, 13.1 cm3 of 0.100 mol dm–3 K2Cr2O7 is required for complete reaction. What is the percentage by mass of Fe in the sample of ferrochrome? A 1.22 B 4.39 C 12.2 D 43.9

Thank you
 
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Tasneem_m98

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Please help O/N/14 paper 13

8 Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute sulfuric acid to produce a mixture of FeSO4 and Cr2(SO4)3. The FeSO4 reacts with K2Cr2O7 in acid solution according to the following equation. 14H+ + 6Fe2+ + Cr2O72– → 2Cr3+ + 6Fe3+ + 7H2O When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid, and the resulting solution titrated, 13.1 cm3 of 0.100 mol dm–3 K2Cr2O7 is required for complete reaction. What is the percentage by mass of Fe in the sample of ferrochrome? A 1.22 B 4.39 C 12.2 D 43.9

Thank you
 
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Tasneem_m98

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Please help O/N/14 paper 13

8 Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute sulfuric acid to produce a mixture of FeSO4 and Cr2(SO4)3. The FeSO4 reacts with K2Cr2O7 in acid solution according to the following equation. 14H+ + 6Fe2+ + Cr2O72– → 2Cr3+ + 6Fe3+ + 7H2O When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid, and the resulting solution titrated, 13.1 cm3 of 0.100 mol dm–3 K2Cr2O7 is required for complete reaction. What is the percentage by mass of Fe in the sample of ferrochrome? A 1.22 B 4.39 C 12.2 D 43.9

Thank you
 
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shazmina

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Xaptor16 said:
oh okay, thankyou! could you help me with this too, if possible please? :)
6 Use of the Data Booklet is relevant to this question. In some countries, anhydrous calcium chloride is used as a drying agent to reduce dampness in houses. The anhydrous salt absorbs enough water to form the dihydrate CaCl 2.2H2O. What is the percentage increase in mass?
A 14%
B 24%
C 32%
D 36%
answer is C
Click to expand...
Your welcome :D
Well this is and easy question and it goes like this ...
First find the Mr of both the compounds .. i mean for CaCl2 ( 111.1g ) and for Cacl2.2H2O ( 147.1g ) .... and then find the increase in percentage using either using the cross multiplication method ( the method which i prefer all the time ) or any other way ....
(147.1*100)/111.1 = 132.4

therefore 132.4-100 = to get the increase in percentage from the standard 100%
which is 32 % .. ie C
Hope you got it ...
 
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shazmina

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Screenshot_19.jpg

The answer for this question is A
Can someone please explain me how compound A shows Methyl Methyl Propenoate ////
 
The Chill Master

The Chill Master

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Metanoia said:
In this case, we divide equally because the question gives us the information that "a single product was obtained after oxidizing."

We don't assume that we divide equally for all other questions unless the clues tells us so.

As for your example of 5 carbons, there is no way to obtain a single product after oxidizing.
Click to expand...
Oh thanks a lot
 
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shazmina

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Screenshot_20.jpg

The Answer is D ...
Can someone please explain me why the answer is D and not C ?? please help ///
 
C

cool Hassan

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plz someone upload that page on which all AS level organic equation were there... its urgent plzz :(
 
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Xaptor16

Xaptor16

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shazmina said:
Your welcome :D
Well this is and easy question and it goes like this ...
First find the Mr of both the compounds .. i mean for CaCl2 ( 111.1g ) and for Cacl2.2H2O ( 147.1g ) .... and then find the increase in percentage using either using the cross multiplication method ( the method which i prefer all the time ) or any other way ....
(147.1*100)/111.1 = 132.4

therefore 132.4-100 = to get the increase in percentage from the standard 100%
which is 32 % .. ie C
Hope you got it ...
Click to expand...
Thankyou so much! I realised what my mistake was, silly as always :p
 
Xaptor16

Xaptor16

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shazmina said:
Screenshot_19.jpg

The answer for this question is A
Can someone please explain me how compound A shows Methyl Methyl Propenoate ////
Click to expand...
I asked my teacher the same question and this is how she explained it to me:
She told me 1) draw propene (keep in mind that the question is talking about Propenoate not propanoate. There's a difference.)
2) make it propenoic acid
3) make an ester with methanol
4) now add a Methyl group to the compound.
You'll see that A is the only possible option
I know that's not very good explanation but I hope you get it :D
 
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shazmina

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Xaptor16 said:
I asked my teacher the same question and this is how she explained it to me:
She told me 1) draw propene (keep in mind that the question is talking about Propenoate not propanoate. There's a difference.)
2) make it propenoic acid
3) make an ester with methanol
4) now add a Methyl group to the compound.
You'll see that A is the only possible option
I know that's not very good explanation but I hope you get it :D
Click to expand...
Wooow i got it ... Thank you so much :D MAy god bless you :)
 
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iYuuki

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Hey guys, can anyone please help me out with these 2 questions?
For the file "Chem2" i need help with 2 (ii) & (iv). Thank you! :)
 

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qwertypoiu

qwertypoiu

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shazmina said:
http://onlineexamhelp.com/wp-content/uploads/2014/08/9701_s14_qp_11.pdf Question 29 of this paper ...
Can anyone please draw and show me all the possible Geometrical isomers that exist for that compound ....
Click to expand...
There are four geometrical isomers. Remember that there are TWO double bonds in the structure, and both are able to have geometrical isomerism. It is difficult to draw them, but imagine this:

FIRST DOUBLE BOND...........SECOND DOUBLE BOND.......
1). cis..........................................cis.................
2). cis........................................trans.................
3). trans......................................cis...........................
4). trans....................................trans...........................


Therefore, there are 4 isomers. In general, if there are x double bonds in a compound that are able to show cis-trans isomerism, there are 2^x geometric isomers of the compound. (eg if there are 3 double bonds, 8 isomers will be seen.)


EDIT: Sorry, it should be three, as cis,trans and trans,cis will be the same, just flipped around; due to this compound's symmetry.
 
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