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# AP Chem - Chapter 10: Gases ## Always Kelvin in Temperature ### Some Background **I. Gases:** * **A.** Expand spontaneously * **B.** Highly compressible * **C.** Low density **II. Pressure:** * **A.** Force exerted on an area * **B.** Most common unit: atm (weight of air per unit of area) *...

# AP Chem - Chapter 10: Gases ## Always Kelvin in Temperature ### Some Background **I. Gases:** * **A.** Expand spontaneously * **B.** Highly compressible * **C.** Low density **II. Pressure:** * **A.** Force exerted on an area * **B.** Most common unit: atm (weight of air per unit of area) * **C.** Other units: 1 atm = 760 torr = 760 mmHg = 101.325 kPa = 1.013 bar (barometer) * **D.** Pressure is caused by gas particles hitting the surface of a container ### STP * **A.** 0°C and 1 atm * **B.** This "standard" applies for gases * **C.** K = 273.15 + °C ### Temperature * **A.** Measures average kinetic energy * **B.** Always use Kelvin for gas problems! (Temperature in °C will go to the negative) ### Basic Gas Laws **I. Boyle's Law:** * **A.** Relates pressure and volume * **B.** $P$ and $V$ are inversely proportional * **C.** $PV = k$ or $V = k(1/P)$ **II. Charles' Law:** * **A.** Relates volume and temperature * **B.** $V$ and $T$ are directly proportional * **C.** $V/T = k$ **III. Gay-Lussac's Law:** * **A.** Relates pressure and temperature * **B.** $P$ and $T$ are directly proportional * **C.** $P/T = k$ **IV. Avogadro's Hypothesis and Law:** * **A.** Relates moles (n) and pressure * **B.** At STP, 1 mol of any gas = 22.4L (don't use for solutions) * **C.** $V$ and $n$ are directly proportional * **D.** $V/n = k$ **Diagram Descriptions:** * **Diagram 1:** Shows a tube with a bulb at one end. One end is open to the atmosphere, the other end is in a vacuum. Mercury (Hg) fills a section of the tube. This diagram helps illustrate pressure differences, including atmospheric and gas pressures. * **Diagram 2:** Shows molecules inside a container colliding against the walls demonstrating how particles exert force on the surface causing pressure. * **Diagram 3 (Boyle's Law):** A graph showing the inverse relationship between pressure (P) and volume (V) * **Diagram 4 (Charles' Law):** A graph showing the direct relationship between volume (V) and temperature (T). * **Diagram 5 (Gay-Lussac's Law):** Graph showing a direct relationship between pressure (P) and temperature (T). * **Diagram 6:** Graph plots Volume of gas against temperature of gas in Celcius. Graph shows data in the negative Celsius region. There also a red dotted line that shows extrapolation to negative values past the visible data. A dotted line and a label indicates absolute zero on the graph. * **Diagram 7:** Graph plots Volume against 1/Pressure (V vs 1/P). The graph shows a linear relationship between them.