Chapter 15-16 study guide

1. Chapter 15-16 study guide Chemistry spring final

2. Solubility and solutions • Factors that affect solubility • -Solute-Solvent Interactions • -Pressure Effects (dissolving gases) • -Temperature Effects (for both gaseous and solid solutes) • Solution • -A solution is a homogenous mixture when one substance (solute) is dissolved into another (solvent). • -An aqueous solution is dissolved in water. • -They are a physical change. • -There are no new substances being produced. • -The particles of the solute and solvent merely physically mix and do not undergo a chemical change.

3. Solute vs. Solvent • -A solute is the substance to be dissolved such as sugar. It is usually a solid and is the smaller part of the solution. • -The solvent is the one doing the dissolving such as water. It accepts the solute. The most common is H20, meaning most solutions are aqueous. • -In a solution of salt and water, salt is the solute and water is the solvent.

4. Dissolution and electrolytes • Rates of Dissolution • -The rate of dissolution quantifies the speed of the dissolution process. • -It depends on the nature of the solvent and solute, temperature, degree of under saturation, presence of mixing, and surface area.   • Electrolytes • -An electrolyte is a substance that dissolves in water to give a solution that conducts electric current • -When ionic solids dissolve in water, the positive and negative ions separate from each other and are free to move around. • -Electrolytes can be strong (all pieces dissociate into ions) or weak (some form ions some don’t).

5. Saturated vs. unsaturated, dilute vs. supersaturated, Miscible and Immiscible • Saturated vs. Unsaturated • -Saturated contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure. • -Unsaturated contains less solute than a saturated solution at a given temperature and pressure. • Dilute vs. Supersaturated • -Dilute is very few particles in the solution. • -Supersaturated contains more solute than it can theoretically hold at a given temperature. • Miscible and Immiscible • -Two liquids are miscible if they dissolve in each other in all proportions. • -Liquids that are insoluble in one another are immiscible.

6. Molarity • -Molarity is an exact way to represent concentration. • -Molarity (M) = # moles of solute in 1 L of solution • -Molarity (M)= # moles of solute (mol) • volume of solution (L) • When given g and L and asked to find M use: M= mol • V • When given mol and L and asked to find V use: V= mol x M • When given M and L and asked to find mol use: mol= V x M

7. Molarity practice problem • Calculate the molarity when 75.0 grams of MgCl2 is dissolved in 500.0 mL of solution. • *Convert mL to L (mLx1000) • *Use molar mass to find moles. Then divide by volume to find M.

8. concentration • -A solution be changed either by adjusting the volume or the solute. • -Adding solvent will dilute concentration. • -Removing solvent increases concentration. • -Formula to help: MiVi=MfVf • -i= initial, f=final • *pay attention to initial and final volumes when doing change in concentration problems

9. Concentration Practice problem • A student pours 60mL of 2.0 HCl acid into a beaker containing 240 mL of water. What is the new concentration of this acid? • *Be sure to use correct final volume.