# What is the total pressure of the gases in the flask at this point?

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Introduced into a 1.30 −L flask is 0.120 mol of #PCl_5(g)# ; the flask is held at a temperature of 227 °C until equilibrium is established.

#PCl_5(g)⇌PCl_3(g)+Cl_2(g)#

What is the total pressure of the gases in the flask at this point? [Hint: Use data from Appendix D in the textbook and appropriate relationships from this chapter.]

From what I know, I need to apply #\DeltaG°# , but I don't know whether I need that for #PCl_5# or #PCl_3# .

Here's the information I got from the book...

for #PCl_5# : -305.0

for #PCl_3# : -267.8

Introduced into a 1.30 −L flask is 0.120 mol of

What is the total pressure of the gases in the flask at this point? [Hint: Use data from Appendix D in the textbook and appropriate relationships from this chapter.]

From what I know, I need to apply

Here's the information I got from the book...

for

for

##### 1 Answer

**Warning! Long Answer.**

#### Explanation:

Yes, you need

**Calculate #ΔG^@# at 500 K**

You can calculate it from the values tabulated at 298 K.

∴ At 227 °C (500 K),

**Calculate #K#**

**Calculate equilibrium concentrations**

Finally, we can set up an ICE table to calculate the equilibrium concentrations.

**Test for negligibility:**

**Calculate total pressure**