Chemistry: Post your doubts here!

[romeopoomore]

Ex

exactly😂 I thought the same way because this question was given by my teacher and I thought I’m missing out something

Or maybe we both are 🤧🤧

 

[romeopoomore]

I

have a question , what’s the purpose of drawing the Hess’a cycle if we can directly do the subtraction method

That's an alternative method .... A faster one for that matter 🔥🔥 Both of them work accurately well but I always prefer drawing the cycle then using the formula to confirm my answer . Unless if it's multiple choice !!!

 

[Madina2410]

That's an alternative method .... A faster one for that matter 🔥🔥 Both of them work accurately well but I always prefer drawing the cycle then using the formula to confirm my answer . Unless if it's multiple choice !!!

What if we get this question CO(g) + 1/2O2(g) CO2(g) ∆H = -284 kJmol-1 , isn’t it oxygen gas is 0 , CO results to -284

 

[Madina2410]

And you should find the formation of CO

What if we get this question CO(g) + 1/2O2(g) CO2(g) ∆H = -284 kJmol-1 , isn’t it oxygen gas is 0 , CO results to -284

 

[romeopoomore]

What if we get this question CO(g) + 1/2O2(g) CO2(g) ∆H = -284 kJmol-1 , isn’t it oxygen gas is 0 , CO results to -284

.
Yes the oxygen is 0 . The backward reaction gives +284 i.e the enthalpy of formation of Carbon monoxide from carbon dioxide is +284 but care is to be taken that this isn't the standard enthalpy of formation of neither CO nor CO2 ... I hope you understand that there's a difference as this are formed from non standard Conditions

 

[Madina2410]

.
Yes the oxygen is 0 . The backward reaction gives +284 i.e the enthalpy of formation of Carbon monoxide from carbon dioxide is +284 but care is to be taken that this isn't the standard enthalpy of formation of neither CO nor CO2 ... I hope you understand that there's a difference as this are formed from non standard Conditions

I don’t understand why we have to do Hess law, what’s its importance any way if we can just do the subtraction method

 

[romeopoomore]

I don’t understand why we have to do Hess law, what’s its importance any way if we can just do the subtraction method

You don't have to apply the Hess Cycle if you don't see the necessity

 

[Madina2410]

Can someone explain this question to me please?

 

[romeopoomore]

View attachment 65243Can someone explain this question to me please?

 

[Madina2410]

Thank you , appreciate It

 

[Madina2410]

Help please

 

[romeopoomore]

View attachment 65246 Help please

View attachment 65246 Help please

I would go for option A because if you write the formulas they result in the same reaction i.e burning carbon results in Only Carbon dioxide under standard Conditions.Moreover it relates to standard Conditions and hence we can trust that it gives the standard enthalpy of formation of CO2
B is wrong for me because bond energies are based on averages and are not entirely standard e.g compare the C and O double bond in acetone,ethanal and carbon dioxide ... They will vary because of the environments the carbon is in .
C is wrong because the combustion of carbon may not necessarily be at standard conditions and hence the enthalpy change of reaction will not necessarily give the standard enthalpy of formation of carbon dioxide
D is wrong because the enthalpy change of combustion from Diamond is non standard

I believe A is the correct answer for those reasons what do you think ?

 

[Madina2410]

Do

I would go for option A because if you write the formulas they result in the same reaction i.e burning carbon results in Only Carbon dioxide under standard Conditions.Moreover it relates to standard Conditions and hence we can trust that it gives the standard enthalpy of formation of CO2
B is wrong for me because bond energies are based on averages and are not entirely standard e.g compare the C and O double bond in acetone,ethanal and carbon dioxide ... They will vary because of the environments the carbon is in .
C is wrong because the combustion of carbon may not necessarily be at standard conditions and hence the enthalpy change of reaction will not necessarily give the standard enthalpy of formation of carbon dioxide
D is wrong because the enthalpy change of combustion from Diamond is non standard

I believe A is the correct answer for those reasons what do you think ?
[/QUO
I was stu

I would go for option A because if you write the formulas they result in the same reaction i.e burning carbon results in Only Carbon dioxide under standard Conditions.Moreover it relates to standard Conditions and hence we can trust that it gives the standard enthalpy of formation of CO2
B is wrong for me because bond energies are based on averages and are not entirely standard e.g compare the C and O double bond in acetone,ethanal and carbon dioxide ... They will vary because of the environments the carbon is in .
C is wrong because the combustion of carbon may not necessarily be at standard conditions and hence the enthalpy change of reaction will not necessarily give the standard enthalpy of formation of carbon dioxide
D is wrong because the enthalpy change of combustion from Diamond is non standard

I believe A is the correct answer for those reasons what do you think ?

i was stuck in between A and B , well I guess I’ll rely on your answer because I’m a novice to AS

 

[romeopoomore]

Do

I am also doing AS 😁

 

[Madina2410]

The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.

what examples are there that makes hydrogen more electronegative hence giving it a negative -1 ?

 

[romeopoomore]

The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.

what examples are there that makes hydrogen more electronegative hence giving it a negative -1 ?

In Sodium Hydride

 

[romeopoomore]

In Sodium Hydride

Oxidation states (oxidation numbers)

Explains what oxidation states (oxidation numbers) are, and how to calculate them and make use of them.

www.chemguide.co.uk

 

[Madina2410]

Hello again, there’s a question that’s rather bothering . Can someone just explain why is it the “b” option

 

[Madina2410]

Hello again, there’s a question that’s rather bothering . Can someone just explain why is it the “b” optionView attachment 65252

And how does the box diagram look like for elements beyond potassium , how do we fill it diagrammatically

 

[Madina2410]

Thank you

Oxidation states (oxidation numbers)

Explains what oxidation states (oxidation numbers) are, and how to calculate them and make use of them.

www.chemguide.co.uk