# Concentration Amount of solute per solvent Different measurements exist of this “dilute” vs. “concentrated”

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Concentration Amount of solute per solvent Different measurements exist of this “dilute” vs. “concentrated”

Molarity (moles solute)/ (L solution) Calculate the molarity of ascorbic acid (C 6 H 8 O 6 ) prepared by dissolving 1.80g in water to make 125 ml of solution. How many ml is needed to provide.0100 mole of ascorbic acid?

Solution Process Solutions are formed when one substance uniformly disperses in another dissolve Solvation- when the solute particles are broken up into small pieces Hydration – when the solute particles are surrounded by water molecules

Energy Total energy of the solution process is actually the sum of the energies of the different parts of the solution process ΔH 1 – always endothermic – energy required to break intermolecular forces in solute ΔH 2 – always endothermic – energy required to break intermolecular forces in solvent ΔH 3 – always exothermic – energy released when solute is surrounded by polar water molecules

Total Heat ΔH t = ΔH 1 + ΔH 2 + ΔH 3 If ΔH 3 is greater than ΔH 1 and ΔH 2, then the overall process is exothermic If not, then process is endothermic Sometimes endothermic dissolving will occur spontaneously if the entropy is increasing (all things tend toward disorder)

Electrolyte Solutes in aqueous solutions as ions Strong Electrolyte – solute ionized completely (highly soluble salts or very polar covalent compounds) NaCl → Na + + Cl - Weak Electrolyte – incomplete ionization occurs (poorly soluble salts or weekly polar) HgCl 2 ↔ HgCl + + Cl - only a small part of the HgCl 2 that is dissolved is present as ions

Non-electrolyte – no ionization occurs (non-polar covalent subtances) Ionic solutes and some very highly polar molecular solutes are electrolytes

Concentration of Electrolytes If each compound below is a strong electrolyte, what is the total concentration of solute particles for each 1) 1.5 M NaCl 2) 0.50 M MgCl 2 3) 0.25 M Ca(NO 3 ) 2 4) 2.5 M K 2 S 5) A mixture of 10 ml of 0.20 M NaCl and 20 ml of 0.40 M Ca(NO 3 ) 2

Example Which of the following would be the best conductor of electricity? The worst? 0.50 M NaCl 0.50 M C 6 H 12 O 6 0.50 M Mg(NO 3 ) 2 0.50 M K 3 PO 4

Vapor Pressure When solutes are added to a solvent, the solvent molecules no longer evaporate at the same rate but they still condense at the same rate Solution end up with lower vapor pressures than pure solvent Results in a higher boiling point and lower freezing point for the solution than the pure solvent

Example Which of the following would have the highest boiling point? Which would have the highest freezing point? 0.50 M NaCl 0.50 M C 6 H 12 O 6 0.50 M Mg(NO 3 ) 2 0.50 M K 3 PO 4

Separating Solutions All solutions can be separated by physical means - filtration - evaporation - sublimation - distillation - chromotography

Distillation Used to separate liquid solution Differential strength in intermolecular attractions result in different boiling points for each liquid in a mixture

Chromatography Different strength of intermolecular interactions between solute and solvent results in different displacement of materials

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