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We have an empty vessel with volume of 2L. We put 2.42gr of PCl5 (g) and allowed it to partially decompose at 250 Celsius according to:

PCl5 --> PCl3 + Cl2

the two prodcuts are also gases. The total pressure inside the vessel after this partial decomposment is 359 torr. What is the partial pressure of each gas now?

I calculated that 0.0116 mol of PCl5 were inserted to the vessel, and I choose x to be the amount of molls of PCl5 that became the 2 products, so we have x molls of PCl3, x molls of Cl2 and 0.0116-x molls of PCl5 at the end. But I don't understand - if we add up this amount we get 0.0116+x molls at the end, but we started from 0.0116 molls of material in the first place... I don't understand how this makes sense...

PCl5 --> PCl3 + Cl2

the two prodcuts are also gases. The total pressure inside the vessel after this partial decomposment is 359 torr. What is the partial pressure of each gas now?

I calculated that 0.0116 mol of PCl5 were inserted to the vessel, and I choose x to be the amount of molls of PCl5 that became the 2 products, so we have x molls of PCl3, x molls of Cl2 and 0.0116-x molls of PCl5 at the end. But I don't understand - if we add up this amount we get 0.0116+x molls at the end, but we started from 0.0116 molls of material in the first place... I don't understand how this makes sense...

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