Gas & Liquid Properties

P V = n R T Pressure (atm) * Volume = number moles * gas constant * Temperature (Kelvin) R=.082

KE = (1/2)(mass)(velocity)2 • At the same Temp, all gases have the same average KE. • Speed increases with temperature, and decreases with mass. • Heavier gases are going to move slower but will have the same KE at that temperature. • Sidenote: At the same temperature, pressure, and volume, there will also be the same number of molecules. PV=nRT

Just look at the PV = nRT fomula. Inverse if both in numerator on same side of equal sign.

P1V1 = P2V2

V1/T1=V2/T2

P1/T1=P2/T2

• Equal volumes of gases at the same T and P have the same number of molecules. • The volume for 1mol of gas at Standard Temperature (273 K) and Pressure (1.00 atm) is 22.4 Liters.

Add 273 T = oC + 273 = K

Divide by 760 1 atm=760 mm Hg

d = m/v d = PM/RT

Diffusion is the gradual mixing of molecules of different gases. • The rate of diffusion (or of effusion) of a gas is directly proportional to temperature and inversely proportional to its molar mass (technically the square root of it)

EFFUSION is the movement of molecules through a small hole into an empty container. • Ex: air escaping knotted balloon through pores • The rate of effusion (and diffusion) is directly proportional to Temperature, and inversely proportional to Molar mass.

• Ptotal in gas mixture = PA + PB + … • Partial pressure of component A = the moles of A divided by total moles (aka the mole fraction of A) X Total Pressure

PV/T is a constant

• The real Pressure is smaller than the ideal Pressure as a result of attractive forces between real gas molecules. They don’t go directly where they’re headed so hit wall less frequently. • a is for attraction. Larger a value means stronger attractive forces. ADD to P to get ideal. • The real Volume is larger than the ideal Volume because real molecules do take up some space. • b is for bigness. Larger b value means larger molecular sizes. Subtract from V to get ideal.

• Ion-dipole attractions • Hydrogen bonding (type of dipole-dipole attraction) • Other Dipole-dipole attractions • Dipole-induced dipole attractions • Induced dipole-induced dipole attractions. (aka London Dispersion Forces, Van der Waal’s Forces)

• You have to have ions. The charged end of the ion interacts with a polar molecule (like water). • Look for polar molecule that dissociates and polar solvent (water). • Acids and bases in water will have ion dipole forces. • Similar to ion-ion except you have one ion and a partial ion which is a dipole. • The force of attraction depends on size of the molecule (how close can the nuclei get) and the size of the charge (Coulomb’s law) • The greater the force of attraction, the more exothermic the hydration enthalpy

• Two permanently polar molecules will be attracted to each other. (Whether the same or different substances.) • Hydrogen bonding is the strongest type of dipole-dipole. • Both molecules need to have a Hydrogen bond between H directly with FON. So both have to have either H-F H-O or H-N. • You can compare the strength for dipole dipole interactions if MM is similar - strength depends on how electronegative the central atom is.

• Hydrogen bonding is the strongest type of dipole-dipole attraction. • Special because nitrogen, oxygen and fluorine are very electronegative and often accompanied by lone pairs in structure. The hydrogen is attracted to their lone pair. • Both molecules need to have a Hydrogen bond between H and either F,O,N. • Tip: having fon • Look for H-O H-F H-N

• Occurs if there are polar and nonpolar molecules in a sample. • One of the molecules is permanently polar, and induces a nonpolar molecule to have a temporary dipole. • The larger a molecule is, the more polarizable it is. • If it’s in water, you’re going to see induced dipole

• Everything will have them. They are the only attractive forces that exist between nonpolar molecules. Polar molecules have them too. • If it so happens that the electrons are all on the other side temporarily, the molecule can induce another temporary dipole moment. • Weak force but higher in molecules with larger molar mass (larger electron cloud, and ↑ polarizability)

• Molecules at the surface experience net inwards force of attraction. • Water molecules at the surface are pulled inwards by its neighbors below (hydrogen bonding)

• The spreading of a liquid across a surface to form a thin film • The IMF between the liquid and surface are about the same strengh as the IMF within the liquid • So the surface must be hydrophillic • If the surface is hydrophobic, it does not have strong IMF forces with water. So the water molecules pull inwards, so only the fewest possible water molecules touch the surface.