Question

When copper metal is added to nitric acid, the following reaction takes place
Cu (s) + 4 HNO₃ (aq) → Cu(NO₃)₂ (aq) + 2 H₂O (l) + 2 NO₂ (g)
Calculate the volume of NO₂ gas collected over water at 25.0 °C when 2.01 g of copper is added to excess nitric acid if the total pressure is 726 mm Hg. The vapor pressure of water at 25.0 °C is 23.8 mm Hg.

Answer 1

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Answer 2

Step 1.
Use the formula
\(P_T = P_{gas} + P_{liquid}\)

\(P_T = 726~mm Hg\)
\(P_{H_2O}=23.6~mmHg\)

Solve for \(P_{gas}\)
Step 2.

You have \(P_{gas}\)
Use Ideal gas law to find volume
PV=nRT
P=Pgas
V = you must find
R = Use constant but this time the pressure is mmHg, and that matters!! So the constant is 62.36
n = Look at the balanced equation. 2.01g of Cu(s) is added. Use stoichiometry to find NO2 gas.
\(2.01g\ Cu\ \cdot\frac{1\ mol\ Cu}{63.55\ g\ Cu}\cdot\frac{2\ mol\ NO_{2}\left(g\right)}{1\ mol\ Cu\left(s\right)} = mol~NO_2\)
T = It's given as 25.0 °C, make sure to convert to Kelvins!

Now solve for V

Answer 3

Thank you!