Gases Chapter 10/11 Modern Chemistry Sections 10.1, 11.1-11.3 The Kinetic Molecular Theory of Matter Gases and Pressure The Gas Laws Gas Volumes and the Ideal Gas Law Chapter 8 Section 1 Describing Chemical Reactions p. 261-275

Chapter 11Section 1 Gases & Pressure p. 361-368 Gases and Pressure Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Pressure = force (in Newtons) per unit area Pressure of a gas is caused by particles of a gas colliding with the walls of its container Pressure (P) of a gas depends on volume (V), temperature (T), and the number of particles (n). Chapter 11Section 1 Gases & Pressure p. 361-368

Pressure & Amount of Gas Insert Holt Visualizing Matter Disc 2 Chapter 11Section 1 Gases & Pressure p. 361-368

Atomospheric Pressure The atmosphere exerts pressure. 78% N, 21% O, 1% other Atmospheric pressure is the sum of the individual pressures of the gases. Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Measuring Pressure Barometer: a device used to measure atmospheric pressure. Developed by Evangelista Torricelli in the early 1600s. Chapter 11Section 1 Gases & Pressure p. 361-368 p. 363

Chapter 11Section 1 Gases & Pressure p. 361-368 Mercury Barometer Chapter 11Section 1 Gases & Pressure p. 361-368 p. 363

Chapter 11Section 1 Gases & Pressure p. 361-368 Aneroid Barometer The aneroid barometer is operated by a metal cell containing only a very small amount of air, or a series of such cells joined together. Increased air pressure causes the sides of the cell or cells to come closer together. One side is fixed to the base of the instrument while the other is connected by means of a system of levers and pulleys to a rotating pointer that moves over a scale on the face of the instrument. Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Measuring Pressure A manometer measures the pressure of a gas in a flask. Chapter 11Section 1 Gases & Pressure p. 361-368 p. 363

Chapter 11Section 1 Gases & Pressure p. 361-368 Manometer Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Units of Pressure The average atmospheric pressure at sea level at 0°C. 760 mm Hg – millimeters of mercury 1.00 atm – atmospheres 101.325 kPa – kilopascals (SI Units) 1 pascal is the pressure exerted by a force of 1 Newton acting on an area of 1 square meter See the table on page 364 Chapter 11Section 1 Gases & Pressure p. 361-368

Table 1 Units of Pressure Chapter 11 Section 1 Gases & Pressure p. 361-368 p. 364

Converting Pressure Units The average atmospheric pressure in Denver, Colorado, is 0.830 atm. Express this pressure in (a) millimeters of mercury (mm Hg) and (b) kilopascals (kPa). p. 365 a. 631 mm Hg b. 84.1 kPa Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Practice Problems p. 365 Convert a pressure of 1.75 atm to kPa and to mm Hg. The critical pressure of carbon dioxide is 72.7 atm. What is this value in units of pascals? p. 365 177 kPa, 1330 mm Hg 2. 7.37 × 106 Pa Chapter 11Section 1 Gases & Pressure p. 361-368

Dalton’s Law of Partial Pressures Partial Pressure: The pressure of each gas in a mixture Dalton’s Law of Partial Pressures: The total pressure of a gas mixture is the sum of the partial pressures of the component gases. PT = p1 + p2 + p3 … Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Partial Pressures Chapter 11Section 1 Gases & Pressure p. 361-368

Law of Partial Pressures Chapter 11Section 1 Gases & Pressure p. 361-368 p. 363

Gases Collected by Water Displacement Chapter 11Section 1 Gases & Pressure p. 361-368 p. 366

Gases Collected by Water Displacement A gas collected over water is a mixture of the gas and water vapor The pressure water exerts is called vapor pressure Insert Holt Visualizing Matter Disc 2 Chapter 11Section 1 Gases & Pressure p. 361-368

Gases Collected by Water Displacement When the water levels inside and outside the tube are the same the PT = Patm Patm = pgas + pH2O or pgas = Patm - pH2O atm atm atm atm PT<Patm PT=Patm PT>Patm Chapter 11Section 1 Gases & Pressure p. 361-368

Gases Collected by Water Displacement The vapor pressure of water varies with temp. p. 859 Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Dalton’s Law Problems Oxygen gas from the decomposition of potassium chlorate, KClO3, was collected by water displacement. The barometric pressure and the temperature during the experiment were 731.0 mm Hg and 20.0°C, respectively. What was the partial pressure of the oxygen collected? p. 367 1. 713.5 mm Hg Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Practice Problems p. 367 Some hydrogen gas is collected over water at 20.0°C.The levels of water inside and outside the gas-collection bottle are the same. The partial pressure of hydrogen is 742.5 mm Hg.What is the barometric pressure at the time the gas is collected? p. 367 1. 760.0 mm Hg Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Ch 11 Sec 1 Homework Page 367 # 1-8 Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11Section 1 Gases & Pressure p. 361-368 Increasing Pressure Insert Glencoe Chemistry Disc 2 Chapter 11Section 1 Gases & Pressure p. 361-368

Chapter 11 Section 2 The Gas Laws p. 369-377 Boyle’s Law TEMP. TEMP. PRESSURE AMOUNT AMOUNT VOLUME Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Boyle’s Law P & V relationship; n & T held constant “The volume of a fixed mass of gas varies inversely with the pressure at constant temperature.” Insert Glencoe Chemistry Matter Disc 2 Chapter 11 Section 2 The Gas Laws p. 369-377 p. 369

Chapter 11 Section 2 The Gas Laws p. 369-377 Boyle’s Law PV = k k is a constant P1 V1 = k P2 V2 = k P1 V1 = P2 V2 V1 V2 P1 P2 Chapter 11 Section 2 The Gas Laws p. 369-377 p. 370

Chapter 11 Section 2 The Gas Laws p. 369-377 Boyle’s Law Problem A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant? p. 370 1. 144 mL O2 Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Charles’ Law TEMP. PRESSURE PRESSURE AMOUNT AMOUNT VOLUME Chapter 11 Section 2 The Gas Laws p. 369-377

Kelvin Temperature Scale Same size degrees as the Celcius scale 0 K = -273.15° C 0 K = absolute zero K = 273 + °C Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Charles’ Law V & T relationship; n & P held constant The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature.” Insert Glencoe Chemistry Matter Disc 2 Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Charles’ Law V / T = k k = a constant V1 / T1 = k V2 / T2 = k V1 = V2 T1 = T2 V2 V1 T1 T2 Chapter 11 Section 2 The Gas Laws p. 369-377 p. 372

Chapter 11 Section 2 The Gas Laws p. 369-377 Charles’ Law Problem A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant? p. 372 1. 815 mL Ne Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Combined Gas Law TEMP. PRESSURE AMOUNT AMOUNT VOLUME Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 Combined Gas Law P, V and T relationship; n held constant “The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.” P 1 V 1 P 2 V 2 = T 1 T 2 Chapter 11 Section 2 The Gas Laws p. 369-377

Chapter 11 Section 2 The Gas Laws p. 369-377 STP Standard Temperature and Pressure Standard Pressure 1.00 atm 760 mm Hg 101.325 kPa Standard Temperature 273 K 0° C Chapter 11 Section 2 The Gas Laws p. 369-377

Combined Gas Law Problems A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.0°C? p. 375 1. 60.0 L He Chapter 11 Section 2 The Gas Laws p. 369-377