In the reaction of C5H12 + O2 = CO2 + H2O, the rate of formation of CO2 is 0.18 M/s. What is the rate of formation for C5H12 in M/s?

Question

Answer choices:

(Δ[O2])/Δt = -0.216

(Δ[O2])/Δt = 0.18

(Δ[O2])/Δt = -0.288

None of the above

(Δ[O2])/Δt = -0.036

Answer 1

First, the reaction as written, is not balanced. We MUST first balance the equation:

C₅H₁₂ + 8O₂ ==> 5CO₂ + 6H₂O ... balanced equation

Secondly, the question makes no sense as written, since it asks for the rate of formation of C₅H₁₂, but C₅H₁₂ isn't being formed, but rather is being used up. If it were being formed, then the reaction would be in the reverse, and O2 would also be being formed. The only choice showing O2 being formed is 0.18 since all other values are negative.

Regardless, we can write the relationships as follows:

-∆[C₅H₁₂]/∆t = -1/8∆[O₂]/∆t = +1/5∆[CO₂]/∆t = + 1/6∆[H₂O]/∆t

-1/8∆[O₂]/∆t = +1/5∆[CO₂]/∆t

-1/8 O₂ = +1/5(0.18 M/s)

-1/8 O₂ = 0.036

O₂ = -0.288