Concentration Measures

Percent Concentration

• Mass percent [ppt = parts/thousand (1mg/L of water); ppb = parts/billion (1 microgram/L of water)]

• Volume percent

Molarity = moles of solute dissolved in 1 L of solution.

Molality = moles of solute dissolved in 1 kg of solvent.

Mole fraction = moles of solute dissolved in total moles of solution = n_a /n

Colligative properties

Vapor pressure lowering

Raoult's Law: P = XP°, where P = vapor pressure of substance in solution, P° = the vapor pressure of the pure substance and X = its mole fraction

• Mole fraction = moles of solute dissolved in total moles of solution = n_a /n

Boiling point elevation

T_b = k_bm, where m = molality = moles solute/kg solvent, and k_b is a constant specific to the solvent.

• Molality = moles of solute dissolved in 1 kg of solvent.

Freezing point depression

T_f = -k_fm, where m = molality = moles solute/kg solvent, and k_f is a constant specific to the solvent.

• Molality = moles of solute dissolved in 1 kg of solvent.

Osmotic pressure ()

V = nRT; or, dividing both sides by V, = MRT, where M = molarity.

• Molarity = moles of solute dissolved in 1 L of solution.

 

 

 

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© R A Paselk

Last modified 30 April 2014