Chemistry: Post your doubts here!

[AnujaK]

Heeyy everyone! I've started a site that'll give you SOLVED past papers! Really helpful! Do check it out Also has some worksheets and revision notes!
https://sites.google.com/site/fromatoscom/

 

[M.Shahzaib Shoaib]

Does anyone have notes for *Electrode Potential* chapter?

The chapter in my text book contains too much extra information.

 

[♣♠ Magnanimous ♣♠]

Hi can anyone please help me with the following questions-
View attachment 46260

The answer is B, if possible can someone please highlight the chiral centres cause i thought it should be C

View attachment 46261
The answer is D, i don't get this one at all.

View attachment 46262
The answer is B though I thought it can equally be A or B.

View attachment 46264
The answer is C

View attachment 46265
The answer is B

View attachment 46267
The answer is C, that is option 2 and 3 is correct.

View attachment 46268
The answer is D

Thank you so much for your effort and time!

Hello it's Magnanimous here and I am really sorry for solving your doubt so late.
Umm, I am gonna start with 9 as I am very poor in Organic Chemistry.


20) I am getting only four isomers of C3H4Cl2.

9) As you will be knowing that HCl is STRONG ACID so for a simple logic the answer will be stong acid too..
So Sodium Hydroxide will be eliminated coz it is a base. For Ethanoic acid it is a weak acid. For sulphuric acid it is more strong acid than HCl so it will produce more concentration og hydrogen ion (maybe) So left is Nitric acid and it is the answer coz HCl and HNO3, when dissolved in water (having same normality) produces same number of H+ ions.

1)
See here Ur is --> Unreacted Oxygen.
I hope you got the calculations which i have done here. Overall I have shown the conversion of volume from Cm3 to dm3 and it's respective ratio.
The ratio is 1:5:3 which means now i can solve the equation by the volume ratio and now let's take this ratios as their moles which means :

1 mole of Hydrocarbon (CxHy)
5 mole of Oxygen (O2)
and 3 mole of Carbon Dioxide (CO2) Now let's make the equation with moles :

1CxHy + 5O2 -----> 3CO2 + H2O

Now if you know balancing the equation you will get :
1C3H8 + 5O2 ----> 3CO2 + 4H2O
So hydrocarbon is C3H8

 

[♣♠ Magnanimous ♣♠]

Hi can anyone please help me with the following questions-
View attachment 46260

The answer is B, if possible can someone please highlight the chiral centres cause i thought it should be C

View attachment 46261
The answer is D, i don't get this one at all.

View attachment 46262
The answer is B though I thought it can equally be A or B.

View attachment 46264
The answer is C

View attachment 46265
The answer is B

View attachment 46267
The answer is C, that is option 2 and 3 is correct.

View attachment 46268
The answer is D

Thank you so much for your effort and time!

Continuations

2) For this just refer this site which also contain example of Cl+2
Here you go : http://www.chemguide.co.uk/analysis/masspec/elements.html

31) C2H5OH + 3.5O2 --> 2CO2 + 3H2O
So now for Combustion of Ethanol you don't get 2.5 moles of Oxygen so obviously other two answer will be correct and you can check it too. ( I have not done but just by a logic I got the answer).

8) sorry Idk this

I hope you got your doubts solved and if any quarries you can surely tell me

 

[Ericyong]

Naturally occuring silicon is a mixture of three isotopes, 28Si, 29Si, and 30Si. The relative atomic mass of silicon is 28.109. What could be the relative abundance of each of the three isotopes?

Help pls I can't figure it out

 

[♣♠ Magnanimous ♣♠]

Naturally occuring silicon is a mixture of three isotopes, 28Si, 29Si, and 30Si. The relative atomic mass of silicon is 28.109. What could be the relative abundance of each of the three isotopes?

Help pls I can't figure it out

where is this ques? can you tell me?

 

[Ericyong]

where is this ques? can you tell me?

http://www.scribd.com/mobile/doc/73549537

Page two first question

 

[Thought blocker]

http://www.scribd.com/mobile/doc/73549537

Page two first question

Vishal

 

[♣♠ Magnanimous ♣♠]

http://www.scribd.com/mobile/doc/73549537

Page two first question

Umm, idk
But we just have to do it by calculations as we calculate relative atomic mass. It's just we have to put x instead of percentage abundance and calculate it. It's all algebra

 

[♣♠ Magnanimous ♣♠]

Vishal

yar tuje pata hai me maths me bohot kaccha hu and isme calculations he aur wo bhi algebra to probs he

 

[Thought blocker]

yar tuje pata hai me maths me bohot kaccha hu and isme calculations he aur wo bhi algebra to probs he

RIP.

 

[♣♠ Magnanimous ♣♠]

http://www.scribd.com/mobile/doc/73549537

Page two first question

what's the answer?
I think it might be C or D coz the Si28 should be the highest in percentage abundance(relative abundance)

 

[♣♠ Magnanimous ♣♠]

kar raha hu ruk muje answer to pata chale kyuki i am a bit unsure in it

RIP.

 

[Ericyong]

what's the answer?
I think it might be C or D coz the Si28 should be the highest in percentage abundance(relative abundance)

The answer is B. I've done some calculations and still couldn't find it.

 

[♣♠ Magnanimous ♣♠]

The answer is B. I've done some calculations and still couldn't find it.

First i thought of B but i didn't have any reason
may be some other person help you as idk this

 

[Thought blocker]

Lemme see.

 

[♣♠ Magnanimous ♣♠]

Lemme see.

yeah see it as this is a type of algebra ques

 

[♣♠ Magnanimous ♣♠]

Naturally occuring silicon is a mixture of three isotopes, 28Si, 29Si, and 30Si. The relative atomic mass of silicon is 28.109. What could be the relative abundance of each of the three isotopes?

Help pls I can't figure it out

http://www.scribd.com/mobile/doc/73549537

Page two first question

ZaqZainab do solve this

 

[AbbbbY]

ZaqZainab do solve this

A: (91.1*28 + 7.9*29+30)/100 = 28.009
B: (92.2*28 + 4.7*29 + 3.1*30)/100 = 28.109

So, B.

The idea is to multiply the relative abundance with the isotopic mass and take the average of the abundances.

Do note, though, that sometimes the three or four or however many abundance percentages are given DO NOT add up to 100%. You've to be careful what you divide with!

 

[AbbbbY]

Hi can anyone please help me with the following questions-
View attachment 46260

The answer is B, if possible can someone please highlight the chiral centres cause i thought it should be C

View attachment 46261
The answer is D, i don't get this one at all.

View attachment 46262
The answer is B though I thought it can equally be A or B.

View attachment 46264
The answer is C

View attachment 46265
The answer is B

View attachment 46267
The answer is C, that is option 2 and 3 is correct.

View attachment 46268
The answer is D

Thank you so much for your effort and time!

I'm a bit late to the party, but I hope this helps
I've only answered the questions that the other guys didn't. Do let me know if I missed anything.

21:

A chiral center is one which has FOUR DIFFERENT groups attached to the central Carbon.

Citric acid has no carbon with 4 entirely different groups.

Isocitric acid, though, has 2 carbons with 4 entirely different groups.

As shown, lets call the top most 1 and the bottom most 3.

C1 has 2 Hydrogens so that's out.
C2 has H, COOH, CH(OH)COOH and CH2COOH. That's 4 different groups. Chiral.
C3 has H, OH, COOH and R (i.e the C(CH2COOH)HCOOH branch). Again, 4 different groups so chiral.

Let me know if this doesn't make sense and I'll draw out the entire acid in a fully displayed form that makes more sense.

20:
7. Simple really. Draw them out. Barely takes a minute if you've practiced chem enough.

In questions like this, your thought process should be something like this:
1- C3X6. 1 double bond.
2- 3 Carbon chain, so double bond position can only be one.
3- No branching possible
4- Make all possible structural isomers first by changing the position of Cl
5- Once you've drawn all structural isomers, identify the isomers which can have cis-trans.

You just have to add the number of isomers that can show cis-trans to the basic structural isomers. In our case, 2 show cis-trans and there are 5 basic, so 5+2 = 7 isomers.

I've also drawn them out for you incase you can't figure them out.

8:

Merely a game of numbers. Focus on the question, don't lose track and it's a freebie, really.

XCl2. Of this, X is 2.920
So, Cl2 = 5.287-2.920 = 2.367g

The idea is to get the mass of X which reacts with 1 mol of Cl2. That Mr = the Ar of X.
2.367 : 2.920
71 : y
y = 87.58 so, Sr.