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Chapter 13 Review. Use the relationship between pressure, temperature, and volume to answer questions. Pressure increases then volume decreases – temperature is constant Pressure decreases then volume increases – temperature is constant
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Use the relationship between pressure, temperature, and volume to answer questions • Pressure increases then volume decreases – temperature is constant • Pressure decreases then volume increases – temperature is constant • Volume increases then temperature increases – pressure is constant • Volume decreases when temperature decreases – pressure is constant
Find the density of 1.0 L of nitrogen at STP (d = PM/RT) • d = (1atm)(28 g/mol) (.0821 atm g/mol K)(273 K) Answer: 1.24 g/L
Find the density of methane CH4 at a pressure of 115 kPa and 45°C. (d=PM/RT) • Need to change kPa to atm first 115 kPa x 1atm = 1.13 atm 101.325 • d = PM/RT d= (1.13 atm) (16 g) (.0821)(318K) Remember to change temperature to Kelvins
An 0.15 cm3 oxygen bubble is released from a diver at a pressure of 186 kPa and a temperature of 6°C. What volume will this bubble have at the surface where the temperature is 13°C and a pressure of 1 atm? • Combine both Charles and Boyle’s Laws and change kPa to atm because units of atm must be the same 186 kPa x 1atm 101.325 • P1 V1 = P2 V2(1.84 atm)(.15 cm3 ) = (1 atm) V T1 T2 279 286 Answer: .26 cm3
A helium balloon will burst above 4 Liters. If it is partially filled (3.4 L) at a temperature of 26°C. If pressure is constant, at what maximum temperature can the balloon be heated to before it bursts? • V1 = V2 T1 T2 3.4 L = 4L 299 T2 Answer: 351.8 Kelvins 78.8°C
Why would it be important for an anesthesiologist to know about gas laws to prevent injury to patients? • Anesthesiologist needs to control temperature and pressure to not hurt or kill the patient
The barometer reads 756 mmHg, what is the atmospheric pressure in kPa? • 756 mmHg x 1atm x 101.325 kPa 760 mmHg 1 atm Answer: 100.79 kPa
Cylinder of nitrogen gas is left in the sun; the temperature reaches 53°C. The cylinder has a volume of 15-L and contains 158 g of nitrogen. What is the pressure in atmospheres inside the cylinder? • PV = nRT • n = m/M Combine both equations to get PV = mRT M P(15) = 158g(.0821)(326) =10.01 atm 28 g/mol
Gas manometer has a pressure of 745 mmHg. Height of mercury is 9 mmHg higher on open end, what is the atmospheric pressure in atm? • 745 mmHg – 9 mmHg = 736 mmHg • 736 mmHg x 1 atm 760 mmHg Answer: .968 atm
Standard temperature • 273 K
Standard pressure • In atm = 1 atm • In mmHg = 760 mmHg • In Pa = 101325 Pa • In kPa = 101.325 kPa
A rising barometer means that atmospheric pressure is • increasing
A falling barometer means that atmospheric pressure is • decreasing
Ideal gas constant has a value of _____ in atm • .0821 atm-L/mol-K
Find the volume of gases at STP – gasses are given in grams • Molar volume of any gas at STP is 22.4 L • Methane CH4 – 32 grams 32/16 = 2 x 22.4 L = 44.8 L • 16 is the molar mass of methane • Water vapor – 36 grams 36/18 = 2 x 22.4 L = 44.8 L • 18 is the molar mass of water • Neon – 50 grams 50/20 = 2.5 x 22.4 L = 56 L • 20 is the molar mass of neon
Statements about ideal gas • Molecules have elastic collisions • Energy remains the same • Has mass • Exerts pressure
Ideal gas law cannot predict behavior of a real gas at • Low temperatures and high pressure
Pressure • Pressure = Force/area
Boyle’s Law • At constant temperature, pressure and volume are inversely proportional
Charles Law • At constant pressure, temperature and volume are directly proportional
To use a manometer you need to • Measure the difference in height of two mercury columns
Relationship between volume and number of moles of a gas • If volume increases so does the number of moles