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19 Nov 2019
CHEM
t Deriving Gas Law Formulas Learning Goal: To understand how to determine the appropriate formula for a given gas law problem. When you are unsure of which formula to use to solve a gas law problem, it is often helpful to make a chart of initial and final values of pressure P volume V, number of moles, n, and temperature T, as shown in the table Initial Final This type of chart will help you to determine which quantities are changing and which quantities remain the same. For example, use the formula Ph Vi PrV2 for the product of pressure and volume at two different points in time when pressure and volume are changing but the number of moles of gas and the temperature are constant. Here is how this formula is derived from the ideal gas law, PV nRT: 1. If n and T are constant, the entire quantity nRT is constant. 2. Therefore, PV is constant. 3. It follows that the quantity PV at any point in time will be the same value as at any other point in time. 4. Therefore Ph Vi 2 V2 Now imagine an experiment where your chart looks like this Initial Final P 2 atm 2 atm V 1.7 L 2.5 L m 0.45 mol 0.45 mol T 273 K It is clear that V and T are the quantities that are changing, while Pand n are constant. To put a constants P, n, and R ogether, we need to do a little bit of algebra: n RT 2. TV 4. T s constant. 5. Therefore the quantity V/T at any point in time will be the same value as at any other point in time, so
CHEM
t Deriving Gas Law Formulas Learning Goal: To understand how to determine the appropriate formula for a given gas law problem. When you are unsure of which formula to use to solve a gas law problem, it is often helpful to make a chart of initial and final values of pressure P volume V, number of moles, n, and temperature T, as shown in the table Initial Final This type of chart will help you to determine which quantities are changing and which quantities remain the same. For example, use the formula Ph Vi PrV2 for the product of pressure and volume at two different points in time when pressure and volume are changing but the number of moles of gas and the temperature are constant. Here is how this formula is derived from the ideal gas law, PV nRT: 1. If n and T are constant, the entire quantity nRT is constant. 2. Therefore, PV is constant. 3. It follows that the quantity PV at any point in time will be the same value as at any other point in time. 4. Therefore Ph Vi 2 V2 Now imagine an experiment where your chart looks like this Initial Final P 2 atm 2 atm V 1.7 L 2.5 L m 0.45 mol 0.45 mol T 273 K It is clear that V and T are the quantities that are changing, while Pand n are constant. To put a constants P, n, and R ogether, we need to do a little bit of algebra: n RT 2. TV 4. T s constant. 5. Therefore the quantity V/T at any point in time will be the same value as at any other point in time, so
Jarrod RobelLv2
26 Jun 2019