Enthalpy of formation equation

Asad_2015

for just say SO_2.

_{Would it be:}

S_(s) + O_2(g) --> SO_2(g)

_or

S_8(g) + 8_02(g)--> 8SO_2(g)i know this is a multiple, and isnt a formation eq as its 8 moles but sulphur exist as s8. so???? explain some one.

also

if we wanted phosphorus tribromide

it would be p4 + 6br2 --> 4pbr3, as it exists as p4. but wud enthalpy eq be p + 3/2br2 --> pbr3.

But how could this work when enthalpy of formation is one mole of substance under standard conditions but these elements exist as tetra or di, wud we do this...

1/8S8 + 02 --> so2

and 1/4p4 + 3/2br3 --> pbr3.

would we do this??? or would we just ignore that sulphur exist as s8 and phosphorus exist as p4 and just use p and s?

Reply 1

Maths help

9

Original post by Asad_2015

for just say SO_2.

_{Would it be:}

S_(s) + O_2(g) --> SO_2(g)

_or

S_8(g) + 8_02(g)--> 8SO_2(g)i know this is a multiple, and isnt a formation eq as its 8 moles but sulphur exist as s8. so???? explain some one.

also

if we wanted phosphorus tribromide

it would be p4 + 6br2 --> 4pbr3, as it exists as p4. but wud enthalpy eq be p + 3/2br2 --> pbr3.

But how could this work when enthalpy of formation is one mole of substance under standard conditions but these elements exist as tetra or di, wud we do this...

1/8S8 + 02 --> so2

and 1/4p4 + 3/2br3 --> pbr3.

would we do this??? or would we just ignore that sulphur exist as s8 and phosphorus exist as p4 and just use p and s?

Hey,
1) suphur and phosphurus exist as pure elements in their standard states

2) the enthalpy change of formation is the mentally change accompanying the formation of ONE MOLE. Therefore it can't be S8 or P4 that react, because during formation it has to be 1 mole that forms, can't be 4 or 8

Make sure to learn this definition: the mentally change of formation is the enthalpy change accompanying the formation of one mole of a substance from its constituent, under standard conditions, with the reactant and products being in their standard states.

Hope that cleared things up :smile:

Reply 2

Asad_2015

OP

12

Original post by Maths help

Hey,
1) suphur and phosphurus exist as pure elements in their standard states

2) the enthalpy change of formation is the mentally change accompanying the formation of ONE MOLE. Therefore it can't be S8 or P4 that react, because during formation it has to be 1 mole that forms, can't be 4 or 8

Make sure to learn this definition: the mentally change of formation is the enthalpy change accompanying the formation of one mole of a substance from its constituent, under standard conditions, with the reactant and products being in their standard states.

Hope that cleared things up :smile:

Sulfur is octatomic in its standard state tho, s8, so enthalpy change wudnt it not be 1/8s8 + 02 --> so2, which will still give one mole. All I'm saying is that sulfur is not S but it's s8 in its standard state. Or am I wrong

Reply 3

Maths help

9

Original post by Asad_2015

Sulfur is octatomic in its standard state tho, s8, so enthalpy change wudnt it not be 1/8s8 + 02 --> so2, which will still give one mole. All I'm saying is that sulfur is not S but it's s8 in its standard state. Or am I wrong

I guess it can also be a solid the single element too.
only one mole can form hence it must be S (s)

just in case i was wrong, i googled it and found this so i assume i'm right, although you may want to double check with your tachers :smile:

https://answers.yahoo.com/question/index?qid=20080211101543AAsssz7

Reply 4

Asad_2015

OP

12

Original post by Maths help

I guess it can also be a solid the single element too.
only one mole can form hence it must be S (s)

just in case i was wrong, i googled it and found this so i assume i'm right, although you may want to double check with your tachers :smile:

https://answers.yahoo.com/question/index?qid=20080211101543AAsssz7

https://answers.yahoo.com/question/index?qid=20131209111449AASfpMi

lollo XD

no to form one mole we can have an eight of the s8, still get one mole.