# Ideal Gas Law Chapter 14 3 Ideal Gas

• Slides: 21

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 = n. R 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 = n. RT

Ideal Gas Constant • R has different numerical values depending on the unit for pressure: – Patm – Pk. Pa – Pmm. Hg R = 0. 0821 R = 8. 314 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 4 th value can be calculated • If P = 3. 18 atm and V = 0. 044 L at 25 o. C, how many moles of gas are present? P = 3. 18 V = 0. 044 T = 25 + 273 = 298

Using the ideal gas law to calculate moles (n) P = 3. 18 V = 0. 044 T = 25 + 273 = 298 PV = n. RT (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) 6. 9 x 10 -3 mol = n

Using the ideal gas law to calculate temperature n = 2. 49 mol V = 1 L P = 143 k. Pa T=? (143) (1) = (2. 49) (8. 314) Tk

Using the ideal gas law to calculate temperature (143) (1) = (2. 49) (8. 314) Tk (143) (1) (2. 49) (8. 314) 6. 91 = Tk - 266 o = o. C = Tk

Using the ideal gas law to calculate volume • n = 0. 323 mol • T= 265 K • P = 0. 900 atm (0. 900) V = (0. 323) (0. 0821) (265) (0. 900) = 7. 821 L

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 = n. RT becomes PV = m. RT M

PV = m. RT M solve for M, and M = m. RT PV