10.3: Gas Phase Reactions

Exercise \(\PageIndex{1}\)

5.00 g of Mg is added to 50.0 mL of 0.800M HCl. A double displacement reaction occurs in a sealed container at 25.0^oC. What is the pressure of the hydrogen gas generated if the volume above the solution is 100.0 ml, and we ignore any pressure due to the evaporated water?

Answer

\(P_{H_{2}}=\frac{n_{H_{2}}RT}{V}=\frac{0.0200mol~H_{2}\left ( 0.08206\frac{L\cdot atm}{mol\cdot K} \right )298K}{0.100L}=4.89atm\)

Exercise \(\PageIndex{2}\)

Nitrogen dioxide is formed in a closed container at 90^oC and 1.00 atm when 1.50 g NO and 2.00 mole of O₂ are mixed. After the reaction is finished the pressure changes to 3.90 atm. What is the final temperature?

Answer

\(T_{2}=T_{1}\left ( \frac{n_{1}}{n_{2}} \right )\left ( \frac{P_{2}}{P_{1}} \right )=363.15K\left ( \frac{2.05mol}{2.025mol} \right )\left ( \frac{3.90atm}{1.00atm} \right )=1433.77K =1400K\)