SOLUTIONS

Aqueous Solution – a short video Aqueous - water that contains dissolved substances Solute Solvent Dissolved particles Dissolving medium Being dissolved Doing the dissolving

15.2 Solvents and Solutes

15.2 Solvents and Solutes If you filter a solution through filter paper, both the solute and the solvent pass through the filter. A solution cannot be separated by filtration. The small size of the solute particles allows them to pass through filter paper.

How Can We Increase Solubility? 16.1 Solution Formation How Can We Increase Solubility?

Stirring and Solution Formation 16.1 Solution Formation Stirring and Solution Formation Bring fresh solvent (the water in tea) is continually brought into contact with the surface of the solute (sugar). More contact with solvent = faster to dissolve (not more to dissolve)

Higher temperature = more kinetic energy 16.1 Solution Formation Temperature and Solution Formation Higher temperature = more kinetic energy More kinetic energy = more molecular movement Equals faster dissolving time and increase in solubility

The bigger the molecule the less soluble it is. 16.1 Solution Formation Particle Size The bigger the molecule the less soluble it is. Smaller “pieces” dissolve faster.

Solubility is often expressed in grams of solute per 100 g of solvent. 16.1 Solubility SOLUBILITY The amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution. Solubility is often expressed in grams of solute per 100 g of solvent.

Solutions Unsaturated Solution Can hold more solute NO equilibrium NO solute on bottom Saturated Solution CANNOT hold more solute Equilibrium Established SOMETIMES solute on bottom (if we add too much)

Factors Affecting Solubility 16.1 Factors Affecting Solubility A supersaturated solution contains more solute than it can theoretically hold at a given temperature. The crystallization of a supersaturated solution can be initiated if a very small crystal, called a seed crystal, of the solute is added. Watch it happen!

Rate of dissolving = rate of crystallization 16.1 Solubility Solution Equilibrium Rate of dissolving = rate of crystallization Occurs only in a saturated solution https://phet.colorado.e du/en/simulation/sol uble-salts In a saturated solution, a state of dynamic equilibrium exists between the solution and the excess solute. The rate of solvation (dissolving) equals the rate of crystallization, so the total amount of dissolved solute remains constant. Inferring What would happen if you added more solute?

You have to know molar mass! 16.2 Molarity Molarity How do you calculate the molarity of a solution? Molarity (M) is the number of moles of solute dissolved in one liter of solution. You have to know molar mass!

16.2 Molarity Molarity Calculate the molarity of a solution which contains 0.40 mol of a substance dissolved in 1.6 L of a solution.

16.2 Molarity Molarity What is the molarity of a solution containing 325 g of NaCl dissolved in 750. mL of solution?

16.2 Molarity Molarity You are making 2.2 L of 3.1 M silver nitrate solution. Who many moles of solute are there?

Colligative Properties 16.2 Molarity Colligative Properties What is happens when salt is added to water And…… We try to freeze it? We try to boil it?

Equilibrium Try this simulations for 2017 https://elearning.cpp.edu/learning-objects/dynamic-equilibrium/ Equilibrium

Can You…. Define Le Chatelier’s Principle? Describe the three ways to change the equilibrium in a system? Predict which direction a reaction will proceed when a stress is applied to a system?

What is Equilibrium Reversible Reactions Products can react to re-form the reactants Shown with a double arrow   Chemical Equilibrium When the rate of the forward equals the rate of the reverse

What is “K” or the Equilibrium Constant? What is Equilibrium What is “K” or the Equilibrium Constant? Less than 1 more reactants present Equilibrium lies to the left Reactant favored Equal to 1 equal amount of product and reactant Neither products or reactants favored Greater than 1 = more products present More products present Equilibrium lies to the right Product favored

What is Equilibrium A Sample Problem Given the data below, calculate the value for the equilibrium constant. 2 NO (g) + Cl2(g) ⇌ 2 NOCl (g) At equilibrium [NO (g)] = 1.20 M [Cl2(g)] = 0.75 M [NOCl (g)] = 0.88 M

Le Chatelier’s Principle If a system is stressed, the equilibrium will shift to relieve the stress Three Methods to Stress A System Add/Remove a substance Change the temperature Change the pressure LEARN BY DOING!!!!!

Change the Pressure Increase pressure = go to side with less gas Decrease the pressure = go to side with more gas 2 NO2(g)  N2O4(g) Increase the pressure = Decrease the pressure =

Change the Temperature Endothermic Reactions Energy as reactant Uses energy Units of energy = kJ = kilojoules Feels cold to the touch Exothermic Reactions Energy as product Produces energy Feels warm to the touch

Change the Temperature Increase temperature – shift away from heat Decrease temperature – shift towards heat 556kJ + CaCO3 (s)  CaO (s) + CO2 (g)   Type of Reaction Increase temperature Decrease Temperature

Change the Concentration If you add, shift away from what you add If you remove, shift towards to remake Adding solids or liquids does not change equilibrium   Example 345kJ + NH4Cl (s) ↔ NH3 (g) + HCl(g) Add NH4Cl Add NH3    Remove HCl Add Heat