Presentation on theme: "Solutions Chapter 10. suspension: particles are so large that they settle out colloid: particles are uneven throughout the sample (positive Tyndall Effect)"— Presentation transcript:
suspension: particles are so large that they settle out colloid: particles are uneven throughout the sample (positive Tyndall Effect) Review of Mixtures: Heterogeneous Homogeneous Heterogeneous Mixtures:
saturated solution: contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. unsaturated solution: contains less solute than the solvent has the capacity to dissolve at a specific temperature.
supersaturated solution: contains more solute than a solvent has the capacity to dissolve at a specific temperature, more than a saturated solution
Solubility Curves The x-axis: Temperature ( o C) The y-axis: Solubility in 100g of water When is the solution saturated, unsaturated, and supersaturated? Temperature o C Solubility in 100g H 2 O
What do you get from a solubility curve? Identify the solubility at a specific temperature. Identify the temperature at which something can dissolve. Identify whether something is saturated, unsaturated, or supersaturated. Identify solubility in different amounts of water. Identify how much will crystallize with a temperature change.
“like dissolves like” Two substances with similar intermolecular forces will be soluble in each other.
non-polar molecules are soluble in non-polar solvents CCl 4 in C 6 H 6 polar molecules are soluble in polar solvents C 2 H 5 OH in H 2 O ionic compounds are more soluble in polar solvents NaCl in H 2 O
Water Molecule Polarity A ________ ____________ has an uneven distribution of electrical charge, which means that each molecule has a _________ __________ region at one end and a __________ __________ region at the other end. The water molecule has a _________ or V-shape, NOT linear H-O-H. The __________ is an electrically negative region that has a greater concentration of _____________. The two _____________ are electrically positive. polar molecule slightly positive slightly negative bent oxygen hydrogens electrons
In the picture of water below, label the atoms and indicate the partial electrical charges. Element: ______ Charge: ______ Element: ______ Charge: ______
Ionic crystals are made up of two types of ions, cations and anions. What charge is associated with a cation? What charge is associated with an anion? In the example sodium chloride, identify the cation and the anion: Sodium: ________ Chlorine: __________
Hydration – What happens when salt dissolves? Color in the molecules and ions below. Next to each molecule and ion identify the charge. Hydrogen: White Oxygen: RedSodium: BlueChlorine: Green DISSOLVED means: surrounded by WATER MOLECULES
What will make a solute dissolve in a solvent faster? 1.Stirring or shaking increase contact between the solute and solvent 2.Break up solute increase the surface area for more contact 3.Increase temperature more collisions between solute and solvent
Electrolytes: When a solute dissolves in water and the solution conducts electricity The electricity comes from the ions that form in solution when the solute is dissolved. Strong and weak electrolytes differ in the degree of ionization. Electrolytes
Strong electrolyte: high conductor because of high number of ions in solution. Non-electrolyte: solution that does not conduct electricity because there are no ions. non-electrolyte weak electrolyte strong electrolyte Weak electrolyte: low conductor because of small number of ions in solution.
Strong Electrolyte – 100% ions Weak Electrolyte – very few ions How do electrolytes conduct electricity? Cations (+) and Anions (-) Non-Electrolyte – no ions THE IONS!!!
Concentration concentration: measure of the amount of solute in a given amount of solvent or solution. measured in: molarity, molality, parts per million (ppm), parts per billion (ppb) The opposite of concentrated is dilute.
M = moles of solute liters of solution Molarity (M) Mol ML Molarity: is the number of moles of solute in one liter of solution.
Example Problem 1 You have 3.50 L of solution that contains 1.54 mol of sodium chloride, NaCl. What is the molarity of that solution?
Example Problem 1 Solution Given: solute = 1.54 mol NaCl solution volume = 3.50 L Unknown: molarity Solution:
Example Problem 2 You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain?
Example Problem 2 Solution Given: volume of solution = 0.8 L concentration of solution = 0.5 M HCl Unknown: moles of HCl Solution:
Boiling-Point Elevation To cook the pasta faster, you add salt to the water. Adding salt to the water is like turning the escape route of the particles into a puzzle. Since it requires more energy to escape, the water boils at a higher temperature (cooking the pasta faster).
What happens when a solution boils? Draw lines to show how the particles on the bottom of the pan boil to the surface through the “puzzle”. This is called boiling point elevation.
What happens when a substance freezes normally?
Freezing-Point Depression In the winter, salt is thrown on the road to melt the ice. When the salt comes in contact with the ice, the ice melts and cannot reform to a solid at the same temperature. Since the salt particles are in the way, it requires a lower temperature to get the water molecules to connect to form ice. Therefore, the water freezes at a colder temperature.
What happens when a solution freezes? Connect the dots below (again with straight lines) this time with salt particles in the way. This is called freezing point depression.
Freezing-Point Depression, continued Molal Freezing-Point and Boiling-Point Constants