<u>Answer:</u> The final pressure in the vessel will be 0.965 atm
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
.....(1)
- <u>For phosphorus trichloride:</u>
Given mass of phosphorus trichloride = 20.0 g
Molar mass of phosphorus trichloride = 137.3 g/mol
Putting values in equation 1, we get:

Given mass of oxygen gas = 3.15 g
Molar mass of oxygen gas = 32 g/mol
Putting values in equation 1, we get:

The chemical equation for the reaction of phosphorus trichloride and oxygen gas follows:

By Stoichiometry of the reaction:
2 moles of phosphorus trichloride reacts with 1 mole of oxygen gas
So, 0.146 moles of phosphorus trichloride will react with =
of oxygen gas
As, given amount of oxygen gas is more than the required amount. So, it is considered as an excess reagent.
Thus, phosphorus trichloride is considered as a limiting reagent because it limits the formation of product.
By Stoichiometry of the reaction:
2 moles of phosphorus trichloride produces 2 moles of 
So, 0.146 moles of phosphorus trichloride will produce =
of 
To calculate the pressure of the vessel, we use the equation given by ideal gas follows:

where,
P = pressure of the vessel = ?
V = Volume of the vessel = 6.00 L
T = Temperature of the vessel = ![210^oC=[210+273]K=483K](https://tex.z-dn.net/?f=210%5EoC%3D%5B210%2B273%5DK%3D483K)
R = Gas constant = 
n = number of moles = 0.146 moles
Putting values in above equation, we get:

Hence, the final pressure in the vessel will be 0.965 atm