Chemical reactions according to equation

[omni]

Homework Statement

12.8 gr of O Flowed over 100 gr hot Al.
and i got this reactions equation: 4Al(s)+3O2(g)--->2Al2O3(g)

a)how many gr Aluminum oxide Al203 Created through a chemical process ?


i know i need to find the number of moles of oxygen which flowed. and the number of moles of Al present.
for the start.

hope u can help me.

 

[Borek]

Do what you know you have to do - what is molar mas of aluminum? Of oxygen? Don't forget oxygen is diatomic.

--

 

[omni]

well the molar mass of Al 27g/mol and of oxygen32g/mol
so the number of moles of O2 in this equation is 0.4 moles because i do 12.8g/32=0.4and for All is 3.7 because i have 100g so i do 100/27=3.7 tell me if i Right till here.

thank you.

 

[Jack the Stri]

Correct, now look at the stoichiometry and see which substance will be limiting for the reaction (i.e. run out first).

 

[omni]

the number of Aluminum oxide Al203 in grams that Created through a chemical process can be 26.52g?

 

[Borek]

Any mass of Al₂O₃ can be created by a chemical process. But in this particular case correct answer is higher, by nearly ³/₄ g.

 

[omni]

look what i did: is known that 12.8g of O was Flowed over 100 gr hot Al.
so the number of moles of O is n=m/Mm=0.4moles of O.
100g of Al so the number of moles is100/27=3.7 moles.
i used all the O and only used in 0.533 moles of Al.
so to know how many gr Aluminum oxide Al203 Created through a chemical process i am take 0.4 moles of the O and doubler it in the Ratio of the moles ?
like this 0.4*2/3=0.26 moles of Al2O3 and the mass is 102*0.26=26.52g of Al2O3 i did it with the equation: n*Mm=m.
hope you Understand me.
thanks.

 

[Borek]

Don't round down intermediate results, round down only the final answer.

 

[omni]

OK but the way is ok?

and the final answer is the mass of Al2O3 that Created through a chemical process is 102*0.26=26.52g tell me where i Wrong ?

i showed you all the way Because maybe i Wrong somewhere in the way so if you see my way you can know where i wrong.

 

[Borek]

I already told you what you did wrong.

 

[omni]

OK so is need to be like this:0.4*2/3=0.2666 moles of Al2O3 and the mass is 101.93*0.2666=27.17g or if i round down this result i will get 27g YES?

thanks for your Patience really.

 

[Borek]

Right.

 

[omni]

wow i so happy i did sure with ur help so thank you about all the help:)