Ideal Gas Law Chapter 14.3

Ideal Gas Law The ideal gas law combines: –pressure –temperature –volume –# of particles (amount)

Increasing Amount of Particles If the amount of gas particles increases: –the pressure will increase OR –the volume will increase

Effects of increased numbers of particles Since P 1 V 1 = P 2 V 2 T 1 T 2 PV = k T stays constant as long as the number of particles stays the same

Effects of increased numbers of particles PV = k T k varies with the amount of gas particles (n) k = nR R was determined experimentally R is called the ideal gas constant

Vocabulary Word ideal gas law: describes the physical behavior of an ideal gas in terms of the temperature, volume and pressure and the number of moles of a gas that are present PV = nRT

Ideal Gas Constant R has different numerical values depending on the unit for pressure: –P atm R = –P kPa R = –P mmHg R = 62.4

Units for the Ideal Gas Law Volume (liters) Temp (Kelvin) n (moles)

Properties of Ideal Gases the gas particles have no intermolecular forces of attraction or repulsion in the real world gas particles DO have a small but measurable volume

Real Gases most gases behave like ideal gases at many temperatures and pressures we can use the ideal gas law to get a very close approximation of experimentally verified values

Real Gases at extremely high pressures or low temperature intermolecular forces become important this allows gases to liquify

Intermolecular Forces size and geometry (shape) can increase the intermolecular forces of attraction, values calculated with the ideal gas law will be off –polar gases (water vapor) –larger gases (butane)

Using the ideal gas law to calculate moles (n) when any 3 values are given, the 4th value can be calculated If P = 3.18 atm and V = 0.044L at 25 o C, how many moles of gas are present? P = 3.18 V = T = = 298

Using the ideal gas law to calculate moles (n) P = 3.18 V = T = = 298 PV = nRT (3.18) (0.044) = n (0.0821) (298)

Using the ideal gas law to calculate moles (n) (3.18) (0.044) = n (0.0821) (298) (3.18) (0.044) = n (0.0821) (298) 6.9 x mol = n

Using the ideal gas law to calculate temperature n = 2.49 mol V = 1L P = 143 kPa T = ? (143) (1) = (2.49) (8.314) T k

Using the ideal gas law to calculate temperature (143) (1) = (2.49) (8.314) T k (143) (1) = T k (2.49) (8.314) 6.91 = T k o = o C

Using the ideal gas law to calculate volume n = mol T= 265K P = atm (0.900) V = (0.323) (0.0821) (265) V = (0.323) (0.0821) (265)= L (0.900)

Using the ideal gas law to molar mass The ideal gas law can be used to determine the molar mass of a gas moles of a gas = mass of the gas molar mass PV = nRT becomes PV = mRT M

PV = mRT M solve for M, and M = mRT PV