Solutions

Classification of Matter Solutions are homogeneous mixtures

A. Definitions Solution -Solution - homogeneous mixture Solvent Solvent - present in greater amount Solute Solute - substance being dissolved

Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda

Solution=Solute +Solvent

Soluble and Insoluble Soluble: when a solute dissolves in a solvent Insoluble: When a solute doesn’t dissolve in a solvent Miscible: When a liquid dissolves in another liquid Immiscible: When 2 liquids don’t dissolve

B. Solvation Solvation –Solvation – the process of dissolving solute particles are separated and pulled into solution solute particles are surrounded by solvent particles

Dissolution of sodium Chloride

Solvents Solvents at the hardware store

C. Johannesson B. Solvation Strong Electrolyte Non- Electrolyte solute exists as ions only - + salt - + sugar solute exists as molecules only - + acetic acid Weak Electrolyte solute exists as ions and molecules View animation online.animation

C. Johannesson B. Solvation NONPOLAR POLAR “Like Dissolves Like”

Saturation of Solutions  A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.  A solution that contains less solute than a saturated solution under existing conditions is unsaturated.

C. Solubility SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

Concentrated vs. Dilute

Concentrated and Dilute A concentrated solution contains more solute than solvent A dilute solution contains more solvent than solute

Solubility Trends  The solubility of MOST solids increases with temperature.  The rate at which solids dissolve increases with increasing surface area of the solid.  The solubility of gases decreases with increases in temperature.  The solubility of gases increases with the pressure above the solution.

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

C. Johannesson C. Solubility Solubility Curve Solubility Curve  shows the dependence of solubility on temperature

Calculations of Solution Concentration Concentration - A measure of the amount of Concentration - A measure of the amount of solute in a given amount of solvent or solution solute in a given amount of solvent or solution 2) Molarity - moles of solute divided by the volume of solution in liters 3) Parts per million – the ratio of parts (mass) of solute to one million parts (mass) of solution 1) Grams per liter - the mass of solute divided by the volume of solution, in liters 4) Percent composition - the ratio of one part of solute to one hundred parts of solution, expressed as a percent

Molarity The concentration of a solution measured in moles of solute per liter of solution. mol = M L

Calculating the molarity 1)If you have 2 moles of glucose in 8 liters of solution what is the molarity of the solution? Molarity= moles per liter Molarity = 2moles / 8 liters =0.25 M

Calculating the molarity 2) If you have 6 moles of glucose in 4 liters of solution what is molarity of this solution? 3) If water is added to 2 mol of glucose to give 5L of solution what is its molarity? 4) A salt solution has a volume of 250ml and contains 0.70mol of NaCl. What is the molarity of the solution?

Calculating the molarity Molarity = moles/liter In the problem we have 250 ml of solution Convert this to liters 250ml/1000ml =0.250L Now calculate the molarity 0.7mol = 2.8 M 0.250L

Calculating the molarity A saline solution contains 0.90 g of NaCl per 100 ml of solution. What is its molarity? Molarity is moles per liter. Convert the concentration to moles per liter. Start with the gram formula mass of NaCl 23.0g+35.5g=58.5g

Molarity contn Now calculate the moles of NaCl We know mole NaCl contains 58.5g How many moles would be present in 0.90g 0.90 x 1.0mole = mole 58.5 g Now convert mol per 100ml to mol per liter Molarity=Moles/liter=0.015/0.1000= 0.15M

Calculating grams of solute How many grams of solute are present in 1.5L of 0.20M Na 2 SO 4 ? Rearrange the equation Liters of solution x molarity =moles of solute Substitute the known in the equation 1.5L x 0.20 =0.30 mol

Calculation contn To determine the weight of solute, multiply the number of moles of Na 2 SO 4 by its mass 1.0 mol contains 142.1g 0.30mol will contain ? 0.30 x 142.1g = 42.6 g 1.0 mol