38) In 2.00 min, 28.9 mL of He effuse through a small hole. Under the same conditions of pressure and temperature, 9.

38) In 2.00 min, 28.9 mL of He effuse through a small hole. Under the same conditions of pressure and temperature, 9.36 mL of a mixture of CO and CO2 effuse through the hole in the same amount of time. Calculate the percent composition by volume of the mixture. The effusion rate of a gas is proportional to its root-mean-square speed, which is related to its molar mass.

37) A 5.87−g sample of graphite was heated with 68.4 g of O2 in a 8.00−L flask. The reaction that took place was

C(graphite) + O2(g) → CO2(g)

After the reaction was complete, the temperature in the flask was 182°C. What was the total pressure inside the flask?

35) Nitrogen dioxide (NO2) cannot be contained in a pure form in the gas phase because it exists as a mixture of NO2 and N2O4. At 25°C and 0.980 atm, the density of this gas mixture is 2.60 g/L. What is the partial pressure of each gas?

Partial pressure of NO2 :

Partial pressure of N2O4 :

32) Nitric oxide (NO) reacts with molecular oxygen as follows:

2NO(g) + O2(g) → 2NO2(g)

Initially NO and O2 are separated in two different chambers connected by a valve. When the valve is opened, the reaction quickly goes to completion. Determine what gases remain at the end and calculate their partial pressures. Assume that the temperature remains constant at 25°C. Initial conditions are as follows:

NO: 3.93 L, 0.500 atm

O2: 2.01 L, 1.00 atm

PNO =  atm

PO2 =  atm

PNO2 =  atm

28a) Calculate the pressure exerted by 2.50 moles of CO2 confined in a volume of 4.24 L at 445 K. What pressure is predicted by the ideal gas equation? The van der Waals constants for CO2 are a = 3.59 atm · L2/mol2 and b = 0.0427 L/mol.

van der Waals equation:

 atm

27) A piece of sodium metal reacts completely with water as follows:

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

The hydrogen gas generated is collected over water at 29.0°C. The volume of the gas is 243 mL measured at 0.979 atm. Calculate the number of grams of sodium used in the reaction. (The vapor pressure of water at 29.0°C = 0.0395 atm.)

21) When coal is burned, the sulfur present in coal is converted to sulfur dioxide (SO2), which is responsible for the acid rain phenomenon.

S(s) + O2(g) → SO2(g)

If 3.26 kg of S are reacted with oxygen, calculate the volume of SO2 gas (in mL) formed at 24°C and 1.07 atm.