Question

When formic acid is heated, it decomposes to hydrogen and carbon dioxide in a first-order decay: HCOOH(g) →CO2(g) + H2 (g) The rate of reaction is monitored by measuring the total pressure in the reaction container.Time (s) . . . P (torr)0 . . . . . . . . . 22050 . . . . . . . . 324100 . . . . . . . 379150 . . . . . . . 408200 . . . . . . . 423250 . . . . . . . 431300 . . . . . . . 435At the start of the reaction (time = 0), only formic acid is present.What is the formic acid pressure (in torr) when the total pressure is 319?

Answer 1

Answer : The formic acid pressure is, 99 torr

Explanation :

The given chemical reaction is:

                            $HCOOH(g)\rightarrow CO_2(g)+H_2(g)$

Initial pressure        a                   0              0

At time 't'                (a-x)                 x              x

According to the Dalton's law,

$P_{Total}=P_{HCOOH}+P_{CO_2}+P_{H_2}$

$P_{Total}=(a-x)+x+x=a+x$    .........(1)

As we are given that:

Initial pressure = a = 220 torr

$P_{Total}=319torr$

Now put the value of 'a' in equation 1, we get:

$P_{Total}=a+x$

$319torr=220torr+x$

$x=99torr$

Thus, the formic acid pressure is, 99 torr