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Solute S A solute is the dissolved substance in a o . l Salt in salt water Sugar in soda drinks u Carbon dioxide in soda drinks t i A solvent is the dissolving medium in a o solution. n Water in salt water Water in soda s

“Like Dissolves Like” Trends Nonpolar solutes dissolve best in nonpolar  The solubility of MOST solids increases with temperature. Fats Benzene  The rate at which solids dissolve increases Steroids Hexane with increasing surface area of the solid. Waxes Toluene  The solubility of gases decreases with increases in temperature. Polar and ionic solutes dissolve best in polar  The solubility of gases increases with the solvents pressure above the solution. Inorganic Salts Water Sugars Small alcohols

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Solubility Chart Therefore… Solids tend to dissolve best when: o Heated o Stirred o Ground into small particles

Gases tend to dissolve best when: o The solution is cold o Pressure is high

Definition of Electrolytes and Saturation of Nonelectrolytes  A solution that contains the maximum amount of solute that may be dissolved under existing An electrolyte is: conditions is saturated.  A solution that contains less solute than a A substance whose saturated solution under existing conditions is conducts an electric current. unsaturated.  A solution that contains more dissolved solute A nonelectrolyte is: than a saturated solution under the same conditions is supersaturated. A substance whose aqueous solution does not conduct an electric current.

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Electrolytes vs. Nonelectrolytes Try to classify the following substances as electrolytes or nonelectrolytes…

1.1.PurePure water 2.Tap water 3.Sugar solution 4. solution The ammeter measures the flow of electrons (current) 5.Hydrochloric acid solution through the circuit. 6.Lactic acid solution If the ammeter measures a current, and the bulb 7.Ethyl alcohol solution glows, then the solution conducts. If the ammeter fails to measure a current, and the 8.Pure bulb does not glow, the solution is non-conducting.

Answers to Electrolytes Ionic Compounds “Dissociate” ELECTROLYTES: NONELECTROLYTES: NaCl(s)  Na +(aq) + Cl -(aq) Tap water (weak) Pure water + - NaCl solution Sugar solution AgNO 3(s)  Ag (aq) + NO 3 (aq) HCl solution Ethanol solution 2+ - MgCl 2(s)  Mg (aq) + 2 Cl (aq) Lactate solution (weak) Pure NaCl + 2- Na 2SO 4(s)  2 Na (aq) + SO 4 (aq)

3+ - AlCl 3(s)  Al (aq) + 3 Cl (aq)

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Ions tend to stay in solution where they can Some covalent compounds IONIZE in solution conduct a current rather than re-forming a solid. Covalent acids form in solution, with the The reason for this is help of the water molecules. the polar nature of the water molecule…

For instance, chloride molecules, Positive ions associate with the negative which are polar, give up their to end of the water dipole (oxygen). water, forming chloride ions (Cl -) and Negative ions associate with the positive hydronium ions (H O+). end of the water dipole (hydrogen). 3

Strong acids such as HCl are completely Weak acids such as lactic ionized in solution. acid usually ionize less than 5% of the time. Other examples of strong acids include:

 Sulfuric acid, H 2SO 4  , HNO 3 Many of these weaker acids  Hydriodic acid, HI are “organic” acids that contain  Perchloric acid, HClO 4 a “carboxyl” group.

The carboxyl group does not easily give up its hydrogen.

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Because of the carboxyl group, organic acids are sometimes called “carboxylic acids”. Other organic acids and their sources include:

o Citric acid – citrus fruit o Malic acid – apples o Butyric acid – rancid butter o Amino acids – protein o Nucleic acids – DNA and RNA o Ascorbic acid – Vitamin C

This is an enormous group of compounds; these are only a few examples.

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