Conquering Chem help: Moles (1 Viewer)

[atrocityx]

there's a few questions i need help with related with moles

30. a] Ethane (C2H6) burns in oxygen to form carbon dioxide and water. how many moles of oxygen are needed to react with one mole of ethane? How many moles of:

(i) CO2 (ii) water are produced?
answer: a) 3.5; (i) 2 and (ii) 3
b] Octane (C8H18) burn in air to form CO2 and H2O. how many moles of oxygen are needed to react with 10 moles of octane and how many moles of water are produced?
answer: 125; 90
31. a] Nitrogen and hydrogen combine to form ammonia, NH3. how many moles of hydrogen are needed to form 40 moles of ammonia?
answer: 60
b] SO2 reacts with oxygen to form sulfur trioxide, SO3. how many moles of oxygen are needed to form 0.6 moles of sulfur trioxide
answer: 0.3
HELP PLEASE? D=
i seriously dont get it and can someone explain ?
thanks.

 

[Fortify]

30a] C2H6 + 7/2O2 -> 3H2O + 2CO2

 

[Fortify]

30b] 10C4H18 + 125O2 -> 80CO2 + 90H2O

 

[Fortify]

31a] N2 + 3H2 -> 2NH3


20N2 + 60H2 -> 40NH3

 

[Fortify]

31b] 2SO2 + O2 -> 2SO3

2 : 1 : 2

0.6 : 0.3 : 0.6

0.6SO2 + 0.3O2 -> 0.6SO3

 

[atrocityx]

30b] 10C4H18 + 125O2 -> 80CO2 + 90H2O

hmm it's not an equation.

 

[Fortify]

I gave you the equation to find the moles. Once you have your equation you look at the number infront of it.

 

[Fortify]

30)A) 7/2 Moles of O2
i) 2 Moles of CO2
ii) 3 Moles of O2

30)B)125 Moles of O2 and 90 Moles of H2O

31)A)60 Moles of H2

B) 0.3 Moles of O2

 

[atrocityx]

30)A) 7/2 Moles of O2
i) 2 Moles of CO2
ii) 3 Moles of O2

30)B)125 Moles of O2 and 90 Moles of H2O

31)A)60 Moles of H2

B) 0.3 Moles of O2

thanks~ but um can you explain it ? O_O" ..

 

[Fortify]

Write out the equations for each reaction (I did that on the above posts). Balance the equations and then that is your ratio for moles needed. Then you just change the ratios to fit the questions.

ie:
30b] C4H18 + 25/2O2 -> 8CO2 + 9H2O

Now the question asks for 10 moles of Octane. Our ratio is 1 : 25/2 : 8 : 9. We need 10 moles of Octane so we multiple everything by 10 for the ratio is 10 : 125 : 80 : 90. The new equation will be:

10C4H18 + 125O2 -> 80CO2 + 90H2O

So now 125 moles of Oxygen is needed for the combustion of 10 moles of Octane. And 90 moles of Water was formed during the combustion.