Solutions Chapter 16

Solutions A solution is a homogenous mixture of 2 substances.

Solvent and Solute The solvent is the dissolving medium in a solution. The solute are the particles that are dissolved in the solution.

Rate of dissolution 3 factors affect how fast something dissolves: – Stirring – Temperature – Surface area (size) of the solute particles

Solubility The solubility of a substance is the amount of solute that dissolves in a given quantity of solvent at a specific temperature and pressure.

Saturation A saturated solution contains the maximum amount of solute possible. An unsaturated solution is a solution that contains less solute than can possibly be dissolved. A supersaturated solution contains more solute than it can theoretically hold.

Can they dissolve? If 2 liquids can dissolve in each other, they are miscible (water and vinegar) If 2 liquids cannot dissolve in each other, they are immiscible (oil and water)

Molarity Molarity (M) is the number of moles of solute dissolved in one liter (1 L) of solution. To calculate the molarity of a solution, divide the moles of solute by the volume of solution: Molarity (M) = moles of solute liters of solution

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 1. Convert grams to moles. 2. Calculate molarity.

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 1. Convert grams to moles g NaCl x 1 mol NaCl= g NaCl

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 1. Convert grams to moles g NaCl x 1 mol NaCl= mol g NaCl Don’t round until the end!

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 2. Calculate molarity. (moles/liters)

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 2. Calculate molarity. (moles/liters) mol NaCl = 0.1L

Practice An IV bag has 0.90 g NaCl in 0.1 L of solution. What is its molarity? 2. Calculate molarity. (moles/liters) mol NaCl = = 0.2 M 0.1L

Practice Again A solution has a volume of.25L and contains 0.70 mol of salt. What is its molarity (M)? Molarity = moles liters

Practice Again A solution has a volume of.25L and contains 0.70 mol of salt. What is its molarity (M)? Molarity = 0.70 mol 0.25 liters=

Practice Again A solution has a volume of.25L and contains 0.70 mol of salt. What is its molarity (M)? Molarity = 0.70 mol 0.25 liters= 2.8 M

Solubility Lab Today: Complete your – Title – Intro (2 paragraphs) – Hypothesis – Materials – Methods – Data Table Next class: conduct the lab, then complete – Data Table – Graph – Conclusion (3 paragraphs) – Literature Cited

Colligative Properties of Solutions A property that depends only upon the number of solute particles, and not upon their identity, is called a colligative property.

3 Colligative Properties 1. Vapor Pressure Lowering – Vapor pressure is the pressure exerted by a vapor on a liquid in a closed system – A solution always has a lower vapor pressure than a pure solvent – Example: salt water has a lower vapor pressure than pure water

3 Colligative Properties 2. Boiling-point elevation – The boiling point of a substance is the temperature at which it turns from liquid to gas – A solution always has a higher boiling point than a pure solvent – Example: salt water has a higher boiling point than pure water

3 Colligative Properties 3. Freezing Point Depression – The freezing point of a substance is the temperature when the liquid becomes solid. – A solution always has a lower freezing point than a pure solvent – Example: salt water has a lower freezing point than pure water

Molality (m) The unit molality (m) is the number of moles of solute dissolved in one kilogram (1kg) of solvent. It is also called molal concentration. Molality = moles of solute kilograms of solvent

Practice Calculate the molality of a solution prepared by dissolving 10.0 moles of salt in 0.60 kg of water. Molality = moles of solute kilograms of solvent

Practice Calculate the molality of a solution prepared by dissolving 10.0 moles of salt in 0.60 kg of water. Molality = 10.0 moles NaCl = 0.60 kg of water

Practice Calculate the molality of a solution prepared by dissolving 10.0 moles of salt in 0.60 kg of water. Molality = 10.0 moles NaCl = kg of water = 17 m

Practice again How many moles of potassium iodide (KI) must be dissolved in 0.50 kg of water to produce a molal KI solution? Molality = moles of solute kilograms of solvent

Practice again How many moles of potassium iodide (KI) must be dissolved in 0.50 kg of water to produce a molal KI solution? m = moles of solute = 0.50 kg water

Practice again How many moles of potassium iodide (KI) must be dissolved in 0.50 kg of water to produce a molal KI solution? m = moles of solute = 0.03 moles KI 0.50 kg water

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 1. Convert grams of salt to moles of salt 2. Convert grams of water to kilograms of water 3. Calculate molality

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 1. Convert grams of salt to moles of salt 20.0 g NaCl x 1 mol NaCl= mol NaCl g NaCl

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 2. Convert grams of water to kilograms of water 600 g water x 1 kg water = g water

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 2. Convert grams of water to kilograms of water 600 g water x 1 kg water = 0.6 kg water g water

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 3. Calculate molality Molality = moles of solute kilograms of solvent

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 3. Calculate molality Molality = mol NaCl = 0.6 kg water

Last practice Calculate the molality of a solution prepared by dissolving 20.0 g of salt in 600 g of water g = 1 kg 3. Calculate molality Molality = mol NaCl = m 0.6 kg water = 0.6 m