Ideal Gas Law Notes PDF

Chemistry Unit General Gas Law and Ideal Gas Law Lesson 3 Table of contents 01 02 03 General Gas Ideal Gases Ideal Gas Law Law  01 Simple Gas Laws Review of Simple Gas Laws General Gas Law Combines all 4 simple gas la...

Chemistry Unit General Gas Law and Ideal Gas Law Lesson 3 Table of contents 01 02 03 General Gas Ideal Gases Ideal Gas Law Law  01 Simple Gas Laws Review of Simple Gas Laws General Gas Law Combines all 4 simple gas laws into one equation from this general law, holding any two conditions constant yields one of the simple gas laws Note: Temperature must be in K Pressure can be in atm, kPa or mmHg but it must be the same for P1 and P2 Volume can be in mL, L, cm3 or dm3 but must be the same for V1 and V2 n = the number of mols Combined Gas Law If the quantity of mols is kept constant, we get the combined gas law This law states that the product of the pressure and volume of a gas sample is proportional to its absolute zero if the quantity of gas is fixed. (n= constant)  Example 1 A certain quantity of gas occupies a volume of 57.0 L at a temperature of 0.0 oC under a pressure of 175.0 kPa. What will the new volume be if the temperature goes up to 32.0 oC under a pressure of 192 kPa?  Example 2 A 350.0 mL sample of helium gas is collected at 22.0 oC and 99.3 kPa. What volume would this gas occupy at STP?  Example 3 A gas occupies a volume of 43.0 L at a temperature of 24.0 oC and a pressure of 189.0 kPa. What would the new temperature have to be in order to double the volume and increase the pressure by 40 kPa?  Example 4 At SATP, 0.150 mol of water vapour occupies a volume of 55.0 ml. What is the new temperature in degrees Celsius if 0.030 mol of water vapour is removed while increasing the pressure to 115.0 kPa and decreasing the volume to 40.0 ml?  02 Ideal Gases Ideal Gases Remember: An ideal gas obeys all of the gas laws regardless of conditions (in reality they don't exist) At extremes of temperature and pressure, REAL gases begin to behave differently from ideal ones. for the most part, when close to STP or SATP, real gases behave like ideal ones, so we can predict their behaviour using the gas laws. Difference between Ideal and Real Gases 03 Ideal Gas Law Ideal Gas Law Describes the relationship between the four variables that characterize a gas sample at any given time: pressure, volume, temperature and quantity These variables can be related by using the gas constant, R  The Gas Constant, R Determined based on the value of the molar volume at STP The value of the gas constant varies depending on the unit of pressure. Pressure in mmHg Pressure in kPa Pressure in atm Example 1 A sample of 4.25 moles of hydrogen at 20.0oC occupies a volume of 25.0 L. Under what pressure is this sample?  Example 2 What volume is occupied by 0.25 grams of O2 measured at 25.0oC and 100.66 kPa? Example 3 When inflated to their max capacity, human lungs contain about 4.09 L of air at 37.0oC. How many moles of air do lungs contain if the air pressure is 100.0 kPa? Molar Mass of a gas The ideal gas law can be used to determine the molar mass of a gas: We replace n in the ideal gas Law to get if we rearrange the formula: Example 4 What is the molecular mass of a gas if 2.82 grams of the gas occupies 3.16 litres at STP? Using the Density of a gas and therefore density must be in g/L Example 5 The density of a certain gas at 27.0oC and 98.66 kPa is 2.53 g/L. Calculate its molecular mass.