Week 4 Practice Problems

# Week 4 Practice Problems - CHEMISTRY 201X Practice Problems...

This preview shows pages 1–2. Sign up to view the full content.

CHEMISTRY 201X September 10-14, 2007 Practice Problems (31) Assume that dry air is composed of 80.0 mole percent nitrogen gas and 20.0 mole percent oxygen gas. (a) Using the ideal gas law, calculate the pressure (in atm) of 30.0 g of air enclosed in a volume of 20.0 L at a temperature of 350.0 K; (b) Use the van der Waals equation of state to estimate the total air pressure (in atm) for the same system in part (a). (HINT: to estimate the pressure, you can take a weighted average of the van der Waals a and b parameters). (32) Oxygen is supplied to hospitals and chemical laboratories under pressure in large steel cylinders. Such cylinders have an internal volume of 28.0 L and contain 6.80 kg oxygen. Use the van der Waals equation to estimate the pressure (in atm) inside this cylinder at 20°C. (33) When 60.0 g methane are placed in a 1.00 L vessel, the pressure is measured to be 130 atm. Calculate the temperature of the gas using (a) the ideal gas law and (b) the van der Waals equation of state. ( a = 2.253 L 2 atm/mol 2 ; b = 0.04278 L/mol). Do you think attractive or repulsive forces dominate in this case? (34) The number density of atoms (chiefly hydrogen) in interstellar space is about 10 atoms per cubic centimeter, and the temperature is about 100 K. (a) Calculate the pressure (in atm) of the gas in interstellar space. (b) Under these conditions, a hydrogen atom collides with another atom once every 10 9 sec (ca. once every 30 years). Use the root-mean-square speed to estimate the distance traveled by a H atom between collisions. The distance between the Earth and Sun is ca. 150 million km. How does your answer compare to this distance? (35)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## Week 4 Practice Problems - CHEMISTRY 201X Practice Problems...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online