Question

Propylene, ${C_3}{H_6}$ , reacts with hydrogen under pressure to give propane, ${C_3}{H_8}:{C_3}{H_6}(g) + {H_2}(g) - - - - > {C_3}{H_8}(g)$ How many liters of hydrogen (at $740$ torr and $24$ degree $C$ ) react with $18.0\;g$ of propylene?

Answer 1

To solve this question, we have to first write the balanced equation and find the number of moles of each compound and using the ideal gas equation we will find the volume of the compound which has been asked.
$\Rightarrow PV = nRT$
Where, $P$ is the pressure, $V$ is the volume, $n$ is the amount of substance, $R$ is the ideal gas constant and $T$ is the temperature.

Complete Step By Step Answer:
First of all, we have to balanced chemical equation:
$\Rightarrow {C_3}{H_6}(g) + {H_2}(g) \to {C_3}{H_8}(g)$
We can see that there is one mole of hydrogen and propylene each, which means the number of moles of propylene is equal to the number of moles of hydrogen that react.
So, number of moles of propylene we have:
$18.0g \times \dfrac{{1\;mole\;propylene}}{{42.08g}} = 0.4278\;moles\;propylene$
And number of moles of hydrogen we have:
$0.4278\;moles\;propylene \times \dfrac{{1\;mole\;hydrogen}}{{1\;mole\;propylene}} = 0.4278\;moles\;hydrogen$
Now, for the volume of hydrogen; we will use the ideal gas law, i.e. the ideal gas law also known as the general gas equation, states that the product of pressure and the volume of the one gram molecule of an ideal gas is directly proportional to absolute temperature. Here $T$ should be in Kelvin and $P$ be in atm so we have to convert the given temperature and pressure which is in degree $C$ and in torr respectively.
$\Rightarrow PV = nRT$
$\Rightarrow V = \dfrac{{nRT}}{P}$
$\Rightarrow V = \dfrac{{0.4278\;moles \times 0.082\dfrac{{atm \times L}}{{mol \times K}} \times \left( {273.15 + 24} \right)K}}{{\dfrac{{740}}{{760}}atm}}$
$\Rightarrow V = 10.705\;L$
$\Rightarrow V \approx 11\;L$ .

Note:
In ideal gas, molecules do not repel or attract each other. There is only one interaction between the molecules of ideal gas that would be an elastic collision with each other or with the wall of the container they are in.