How many moles of Fe are needed for the reaction of 12.0
moles of O2?

The balanced reaction equation is:

4

F

e

(

s

)

+

3

O

2

(

g

)

→

2

F

e

2

O

3

(

s

)

Initial moles of oxygen reactant (given) =  

12.0

m

o

l

According to the balanced equation the iron and oxygen reactants combine in a 4:3 molar ratio. Therefore for complete consumption of both reactants we require:

Initial moles of iron reactant =  

4

3

×

12.0

m

o

l

=

16.0

m

o

l

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds