Chemistry: Post your doubts here!

[LeoMessi]

Q. 11 isn't an equilibrium question; it's the activation energy question.

Sorry , Q 11 for this paper please

 

[Aries_95]

Sorry , Q 11 for this paper please

Answer by h4rriet

 

[cute97]

21. The functional groups that react with Na are CO2H and OH, so three of any of these should be present in the compound. B and D are ruled out. NaOH will react with CO2H, so there should be 1 CO2H and 2 OH groups.
22. Find the molecular mass of the products of the hydrolysis of ethyl propanoate. Then find the % by mass.
23. The compound is an ester and will get hydrolysed by the acid.

Thank you but for q21 WHAT ABT the -1 and -3 charges and how did you knw that there should be 1 CO2H and 2 OH grps
Q22 yhh but how sry but am a little bad in chem
Q23 yhh all four answers have COOH grp ?? plz ans

 

[Dr.MMM]

"NaOH will react with CO2H, so there should be 1 CO2H and 2 OH groups." This part please
As for the second question the products will be ethanol and propanoic acid in the ratio 1:1 right?

 

[h4rriet]

Sorry , Q 11 for this paper please

Q. 11: Draw ICE charts for A, B, C and D. That is, initial moles, change in moles and equilibrium moles.
For B, it'll be like this:

 

[Student12]

how does NF3 have 6 bonding pair ?

 

[h4rriet]

Thank you but for q21 WHAT ABT the -1 and -3 charges and how did you knw that there should be 1 CO2H and 2 OH grps

"NaOH will react with CO2H, so there should be 1 CO2H and 2 OH groups." This part please
As for the second question the products will be ethanol and propanoic acid in the ratio 1:1 right?

They're saying that the compound reacts with Na to give a 3+ charged ion. Only OH and CO2H react with Na to give a 1+ charged ion, so there must be 3 functional groups, either CO2H or OH. When NaOH reacts, a compound with a 1+ charge is produced by CO2H only, not OH. That means there is only ONE CO2H in the compound we're talking about. So there is ONE CO2H and TWO OH groups, that makes it 3 overall. So they can react with Na to give a 3+ charged ion and with CO2H to give a 1+ charged ion.

 

[h4rriet]

how does NF3 have 6 bonding pair ?

It doesn't.

 

[LeoMessi]

Answer by h4rriet

Thanks alot.
Could you please answer Q9 of this paper as well. And could you please work out the answer for all the options if its not a problem.
Thanks once again for ur time and effort.

 

[h4rriet]

Q22 yhh but how sry but am a little bad in chem
Q23 yhh all four answers have COOH grp ?? plz ans

22. Ethyl propanoate will give ethanol and sodium propanoate when hydrolysed with NaOH. Find the molecular masses of both, and then find the % by mass. For example, to find the % by mass of ethanol, do (mass by ethanol)/(mass of ethanol + sodium propanoate).
23. Yes, but you have to take into account the number of C atoms as well.

 

[darkxangel]

Propanone has the molecular formula C3H6O.
The enthalpy change of combustion of hydrogen is –286kJmol–1
.
The enthalpy change of combustion of carbon is –394kJmol–1
.
The enthalpy change of combustion of propanone is –1786kJmol–1
.
Using this information, what is the enthalpy change of formation of propanone?
A –1106kJmol–1
B –540kJmol–1
C –254kJmol–1
D +1106kJmol–1

I need help in this question.!

 

[LeoMessi]

Q. 11: Draw ICE charts for A, B, C and D. That is, initial moles, change in moles and equilibrium moles.
For B, it'll be like this:

Thanks alottttt!!!!!!!!!!

 

[Dr.MMM]

They're saying that the compound reacts with Na to give a 3+ charged ion. Only OH and CO2H react with Na to give a 1+ charged ion, so there must be 3 functional groups, either CO2H or OH. When NaOH reacts, a compound with a 1+ charge is produced by CO2H only, not OH. That means there is only ONE CO2H in the compound we're talking about. So there is ONE CO2H and TWO OH groups, that makes it 3 overall. So they can react with Na to give a 3+ charged ion and with CO2H to give a 1+ charged ion.

Thanks

A number of alcohols with the formula C4
H10O are separately oxidised. Using 70g of the alcohols
a 62% yield of organic product is achieved.
What mass of product could be obtained?
1 42.2g of butanone
2 51.6g of butanoic acid
3 51.6g of 2-methyl propanoic acid

 

[h4rriet]

Propanone has the molecular formula C3H6O.
The enthalpy change of combustion of hydrogen is –286kJmol–1
.
The enthalpy change of combustion of carbon is –394kJmol–1
.
The enthalpy change of combustion of propanone is –1786kJmol–1
.
Using this information, what is the enthalpy change of formation of propanone?
A –1106kJmol–1
B –540kJmol–1
C –254kJmol–1
D +1106kJmol–1

I need help in this question.!

Draw a Hess cycle.

 

[h4rriet]

Thanks

A number of alcohols with the formula C4
H10O are separately oxidised. Using 70g of the alcohols
a 62% yield of organic product is achieved.
What mass of product could be obtained?
1 42.2g of butanone
2 51.6g of butanoic acid
3 51.6g of 2-methyl propanoic acid

Find the molecular mass of butanone, butanoic acid and 2-methyl propanoic acid. Then find the yield using actual mass/calculated mass x 100. Choose the options whose yield = 62 %.

 

[magnesium]

http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w12_qp_12.pdf
15,17 ?some1 HELP

 

[Alice123]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q4 h4rriet

 

[magnesium]

h4rriethttp://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w12_qp_12.pdf
15,17 ?some1 HELP

 

[Dr.MMM]

i

Find the molecular mass of butanone, butanoic acid and 2-methyl propanoic acid. Then find the yield using actual mass/calculated mass x 100. Choose the options whose yield = 62 %.

m getting 58.6% for all of the three options, can you please solve any one option?

 

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w12_qp_12.pdf
15,17 ?some1 HELP

15. In the equation for the decomposition of a Group II metal nitrate, the metal nitrate and the metal oxide have a mole ratio of 1:1. So (mass of nitrate)/(molecular mass of nitrate)=(mass of metal oxide)/(molecular mass of metal oxide). The mass of nitrate is given to be 2 grams. The mass of the metal oxide will 2 minus the mass of gas produced.
17. Find the moles of O2 from the information given. Write a balanced equation for the combustion of Ca and Mg. Then use mole ratios to determine whether the metal is Ca or Mg.