In: Chemistry
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 0.43 atm before any reaction takes place. The kinetics of the
reaction are then followed by measurements of total pressure and
these data are obtained:
t(s) | 0 | 1000 | 3000 | 7000 |
PTotal (atm) | 0.43 | 0.50 | 0.59 | 0.68 |
Question:
Find total pressure after 1.39×104 s .
To determine the order of the reaction, first P-x is calculated for different time intervales where P is the initial pressure (0.43 atm, the initial pressure of acetaldehyde) and x is the change in the pressure of acetaldehyde at time t.
A graph of t vs 1/P-x is plotted which gives a strainght line equation. This indicates first order reaction.
The slope is 2164.8 and the y intercept is -5023.
Hence, the rate law expression becomes
Substitute
in the above expression.
Hence,
But P is 0.43,
Hence,
The total pressure is
atm.