At 700 K acetaldehyde decomposes in the gas phase to methane and carbon monoxide

Question

At 700 K acetaldehyde decomposes in the gas phase to methane and carbon monoxide. The reaction is:
CH3CHO(g)CH4(g)+CO(g)

A sample of CH3CHO is heated to 700 K and the pressure is measured as 0.25 atm before any reaction takes place. The kinetics of the reaction are then followed by measurements of total pressure and these data are obtained:

Rate = - dPCH3CHO/dt = 4.5 * 10-4 atm * -1 P CH3CHO2

Find total pressure after 1.20×104s .

Express your answer to two significant figures and include the appropriate units.

Ptotal = ______ ?

Explanation / Answer

The partial pressure of CH3CHO = Pressure of [CH3CHO] / Total pressure

At the end of reaction the total pressure = 2X P0 = 0.5 atm

So the partial pressure of CH3CHO = 2P0 - Pt

a) at t = 0

Partial pressure = 0.5 -0.25 = 0.25

b) at t = 1000

Partial pressure = 0.5 - 0.28 = 0.22

c) at t = 3000

Partial pressure = 0.5 -0.31 = 0.19

d) at 7000

Paritla pressure = 0.5 - 0.36 = 0.14

Now if we plot the graph between Time and 1 /P and we are obtaining a straight line then the reaction is of second order

The straight line corresponds to the following equation

1/ p = 1/ p0 + kt

p0 = initial pressure = 0.25

at time t = 12000 seconds

1/pressure = 0.0004 X 12000 + 4 .0

1/ Pressure = 8.8

Pressure = 1/8.8 = 0.114

he partial pressure of CH3CHO = 2P0 - Pt

Ptotoal = 0.5 - 0.114 = 0.386 atm

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.