When gaseous F2 and solid I2 are heated to high temperatures, the I2 sublimes and gaseous iodine heptafluoride forms. If 350. torr of F2 and 2.50 g of solid I2 are put into a 2.50-L container at 250. K and the container is heated to 550. K, what is the final pressure (in torr)? What is the partial pressure of I2 gas?

Respuesta :

Answer:

[tex]P_{I2}=0.033atm[/tex]

Explanation:

Hi, the first step is to calculate how much F2 there is in the container:

Fluorine can be considered as an ideal gas (given that is non-polar and has a small molecule). Using the ideal gas formula:

[tex]n=\frac{V*P}{T*R}[/tex]

Where:

[tex]P=350 torr * \frac{1 atm}{760 torr}=0.46atm[/tex]

[tex]T=250K[/tex]

[tex]V=2.5 L[/tex]

[tex]R=0.082 \frac{atm*L}{mol*K}[/tex]

[tex]n=\frac{2.5L*0.46atm}{250K*0.082 \frac{atm*L}{mol*K}}[/tex]

[tex]n=0.056 mol[/tex]

Now, the mols of iodine:

[tex]n_{I2}=\frac{2.5g}{253.8 g/mol}[/tex]

[tex]n_{I2}=9.85*10^{-3}mol[/tex]

The chemical reaction described is the following:

[tex]I_2(g) + 7 F_2(g) \longrightarrow 2 IF_7(g)[/tex]

In this case, the limitant reactant is the fluorine:

1) The 0.056 mol of F2 gives [tex]8*10^{-3} mol[/tex] of [tex]IF_7[/tex] and consumes [tex]8*10^{-3} mol[/tex] of I2.

2) At the end, in the conteiner we have:

[tex]8*10^{-3} mol[/tex] of [tex]IF_7[/tex]

[tex]0 mol[/tex] of [tex]F_2[/tex]

[tex]9.85*10^{-3}-8*10^{-3}=1.85*10^{-3} mol[/tex] of [tex]I_2[/tex]

In total: [tex]9.85*10^{-3}mol[/tex] .All in 2.5 L at 550 K

The final pressure:

[tex]P=\frac{T*R*n}{V}[/tex]

[tex]P=\frac{550K*0.082 \frac{atm*L}{mol*K}*9.85*10^{-3}mol}{2.5L}[/tex]

[tex]P=0.176 atm[/tex]

The partial pressure:

[tex]P_{I2}=0.176atm*\frac{1.85*10^{-3} mol (I2)}{9.85*10^{-3} mol (total)}[/tex]

[tex]P_{I2}=0.033atm[/tex]

Note: this partial pressure is calculated by the Dlaton's principle

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