The volume of NO₂ gas collected over water at 25.0 °C is 4.71 liters.
We can solve this problem in the following steps:
Calculate the moles of copper used.
Molar mass of Cu: 63.55 g/mol
Moles of Cu used: 5.45 g / 63.55 g/mol = 0.0857 mol
Calculate the moles of NO₂ produced.
From the balanced equation, 1 mol of Cu produces 2 mol of NO₂.
Moles of NO₂ produced: 0.0857 mol Cu * (2 mol NO₂ / 1 mol Cu) = 0.1714 mol
Convert temperature to Kelvin.
K = °C + 273.15
K = 25.0 °C + 273.15 = 298.15 K
Calculate the partial pressure of NO₂.
Total pressure: 726.0 mmHg
Vapor pressure of water at 25.0 °C: 23.8 mmHg
Partial pressure of NO₂: 726.0 mmHg - 23.8 mmHg = 702.2 mmHg
Apply the Ideal Gas Law to calculate the volume of NO₂.
Ideal Gas Law: PV = nRT
P: partial pressure of NO₂ in atm (702.2 mmHg / 760 mmHg/atm = 0.924 atm)
V: volume of NO₂ in liters (unknown)
n: moles of NO₂ (0.1714 mol)
R: Ideal Gas Constant (0.0821 L atm / mol K)
T: temperature in Kelvin (298.15 K)
V = nRT / P
V = 0.1714 mol * 0.0821 L atm / mol K * 298.15 K / 0.924 atm
V = 4.71 L
Therefore, the volume of NO₂ gas collected over water at 25.0 °C is 4.71 liters.