Thermodynamics help?

Question

I'm studying for a quiz and need help doing the following problems: ( Ihave the answer I just need help with the process)

2 C6H14 (l) + 19 O2 (g) ==> 12 CO2 (g) + 14 H20 (l)
where the delta H = -2005 kcal

How many liters of oxygen at STP are needed to produce 1234 kcals? (ans. 261.9 liters)

If 164 gr of CO2 is produced, how much energy is also produced? (ans. 623 kcals)

and with

2 Mg (s) + O2 (g) ==> 2 MgO (s)
where delta H = -288 kcal

If 17.7 grams of MgO is produced, how many kcals are also produced? (ans. 63 kcals)

Answer 1

x/1234 KC = (19)(22.4)/2005 KC)
x = 261.94 L

x/164 g = 2005/(12*44 g)
x = 622.76 kcal.

x/17.7 = 288/(2*40.31)
x = 63.230 kcal.