Edexcel CHEMISTRY DOUBTS!!!!

[The Golden Girl =D]

Thanks . It's Okay my teacher explained it in detail 

[The Golden Girl =D]

Hmm Okay i got this doubt

when C (s) + 2 H 2 (g) --> CH4 (g)

             it's atoms r C (g) + 4 H

what i don't get is :

 1. how the hell do i know that delta H of hydrogen is Atomization ?

cuz when we solve it this is how we solve it :

4 delta H - delta H atomization of Carbon + 4 delta H atomization of Hydrogen

I know it's a stupid Question but it's been taking me toooooooooo long to think y is it atomization for the HYDROGEN   , it was gas and then gas so no atomization ? idk 

PLZ someone help 

[Deadly_king]

Hmm Okay i got this doubt

when C (s) + 2 H 2 (g) --> CH4 (g)

             it's atoms r C (g) + 4 H

what i don't get is :

 1. how the hell do i know that delta H of hydrogen is Atomization ?

cuz when we solve it this is how we solve it :

4 delta H - delta H atomization of Carbon + 4 delta H atomization of Hydrogen

I know it's a stupid Question but it's been taking me toooooooooo long to think y is it atomization for the HYDROGEN   , it was gas and then gas so no atomization ? idk 

PLZ someone help 

The definition for standard enthalpy change of atomisation :

It is the heat energy change when 1 mole of separate gaseous atom of the element is formed from the element under standard state conditions.

Hydrogen exists as H₂ molecules under standard state conditions. So you must not omit the delta H atomization of hydrogen since the H₂ molecule need to be converted to H atoms.

Do you get me??
If not.......let me know and i'll try to get clearer

[The Golden Girl =D]

The definition for standard enthalpy change of atomisation :

It is the heat energy change when 1 mole of separate gaseous atom of the element is formed from the element under standard state conditions.

Hydrogen exists as H₂ molecules under standard state conditions. So you must not omit the delta H atomization of hydrogen since the H₂ molecule need to be converted to H atoms.

Do you get me??
If not.......let me know and i'll try to get clearer

Aha ya i get it  ... thanks loads Mate

[Deadly_king]

Aha ya i get it  ... thanks loads Mate

You are welcome dear

[helai.j]

can some one give me some Questions to practice for deducing orders and rate Equations ?
and can any one solve A2 edexcel chemistry ann fullick page 15, 2 Questions please ?

[helai.j]

in the rate of reaction Questions, if the data  given is Pressure of the reactant and time, how do i convert the pressure into concentration to draw a concentration/time graph ? 

please someone answer ?

[Deadly_king]

in the rate of reaction Questions, if the data  given is Pressure of the reactant and time, how do i convert the pressure into concentration to draw a concentration/time graph ? 

please someone answer ?

Hmm.......can you please upload or write the whole question??

I don't think I can help you with only this little information 

[helai.j]

there is a Question in A2 chemistry ann fullick book page 19 it says

Q: in a gas phase, molecule A decomposes to molecule B and C at high temperature. A chemist suspects that this reaction is first order with respect to A. in an experiment to explore the kinetics of the reaction, the data in the table were obtained for the decomposition at 800K.

then there is a table with time and partial pressure values for A .
example

T            A/KPA
0               1300
20             1051

and so on, then it says by using a graph find out if this reaction is really first order with respect to A.
for the graph i need concentration/time .  but they have given me pressure. so how will i make the graph ? or turn the pressure into conc. ?

[The Golden Girl =D]

Hmm .. i have a Q ...." Concentration = Mass/Volume "is there such a formula that exists ?

And if yes then where Am i supposed use it ?

Thx

Plz this is Urgent .

[Deadly_king]

Hmm .. i have a Q ...." Concentration = Mass/Volume "is there such a formula that exists ?

And if yes then where Am i supposed use it ?

Thx

Plz this is Urgent .

Indeed it exists.

Concentration can be expressed in two units name g/dm³ and mol/dm³

When you are asked to find concentration in terms of g/dm³ then you use the formula. Same principles are applied.

Concentration in g/dm³ = Mr x Concentration in mol/dm³

This is an equation which you need to know as well and will be helpful to you in your calculations.

Hope it helps

[The Golden Girl =D]

Indeed it exists.

Concentration can be expressed in two units name g/dm³ and mol/dm³

When you are asked to find concentration in terms of g/dm³ then you use the formula. Same principles are applied.

Concentration in g/dm³ = Mr x Concentration in mol/dm³

This is an equation which you need to know as well and will be helpful to you in your calculations.

Hope it helps

Ya the Equation does Help but can u explain to me where exactly Ami going to need Concentraction = mass/volume . ...cuz the teacher gave me a H.W. and i solved it ALL in this equation and i got so many mistakes , idk y 

[Deadly_king]

Ya the Equation does Help but can u explain to me where exactly Ami going to need Concentraction = mass/volume . ...cuz the teacher gave me a H.W. and i solved it ALL in this equation and i got so many mistakes , idk y  

Hmm.......the way that equation is used will vary with question.

Normally your are given that a certain mass x is dissolved in 100cm3 of solution.

So first you need to find the mass present in 1dm3 of the solution.
Therefore concentration will be the mass calculated in 1 dm3.

It's almost the same principles you apply when using moles to find concentration.

If you have a question, i'll be be able to explain it better

[The Golden Girl =D]

Hmm.......the way that equation is used will vary with question.

Normally your are given that a certain mass x is dissolved in 100cm3 of solution.

So first you need to find the mass present in 1dm3 of the solution.
Therefore concentration will be the mass calculated in 1 dm3.

It's almost the same principles you apply when using moles to find concentration.

If you have a question, i'll be be able to explain it better

Well i do NOT have a Q , cuz so far we did NOT use it at ALL .....so idk ....the only thing iwant to know is the new Equations like this and how to use them , Thanks

[helai.j]

can someone please explain this for me ? Question from rate of reaction chapter from A2 chemistry edexcel .

Q: the reaction between nitrogen dioxide and carbon monoxide fits the following overall equation:
NO₂  + CO ---> NO + CO₂

a) if the rate equation suggested a single step mechanism, what would be the rate equation?
b) the rate equation for this reaction is in fact :  rate=k[NO₂]²

A possible mechanism is:
2NO₂ --> NO₃ + NO        ( step 1 )
NO₃ + CO --> NO2 + CO₂   ( step 2 )

which of these steps do you think is the rate determining  step? explain your answer.