Solutions

A solution is a homogenous mixture of 2 or more substances. The solute is(are) the substance(s) present in the smaller amount(s). What is being dissolved. The solvent is the substance present in the larger amount. What is doing the dissolving.

How do substances dissolve? Solvent particles collide with solute particles Dissolving depends on forces between particles “Like dissolves like”

Rate of Solution Factors that affect the rate of solution (how fast the solute dissolves): – Temperature – Pressure – Surface Area – Agitation

A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.

Solubility Curves These curves represent saturated solutions. Using these graphs, you can determine how many grams will dissolve at specific temperatures.

Learning Check S1 At 40  C, the solubility of KBr is 80 g/100 g H 2 O. Indicate the solubility of the solutions: A. ___80 g KBr in 100 g of water at 40  C B. ___100 g KBr in 100 g of water at 40  C C. ___150 g KBr in 200 g of water at 40  C D. ___0.25 moles KBr in 50 g of water at 40  C

Temperature and Solubility Solid solubility and temperature Some compounds (usually solids) increase solubility with increasing temperature Some compounds (usually gases) decreases solubility with increasing temperature

Learning Check S2 A. Why would you want to dissolve your sugar in tea while it is hot as opposed to when it is cold? B. Why would a bottle of carbonated drink possibly burst (explode) when it is left out in the hot sun ? C. Why would fish die in water that gets too warm?

Chemistry In Action: The Killer Lake Lake Nyos, West Africa Lake Nyos – formed from a former volcano that deposited large quantities of CO 2 at the bottom of the lake. It is not sure of the exact cause, but at some instant, 1.6 million tons of CO 2 was released from the bottom of the lake. As the gas erupted and covered the land, all oxygen was displaced and over 1,700 individuals and over 3,500 livestock were killed due to asphyxiation.

Molarity The molarity of a solution is a representation of its concentration. It represents the amount of moles of the solute compound dissolved in 1 Liter of the solution. Molarity (M) = moles of solute Liter of solution

Units of Molarity 2.0 M HCl = 2.0 moles HCl 1 L HCl solution 6.0 M HCl= 6.0 moles HCl 1 L HCl solution

Molarity Calculation NaOH is used to open stopped sinks, to treat cellulose in the making of nylon, and to remove potato peels in factories. If 4.0 g NaOH are used to make 500. mL of NaOH solution, what is the molarity (M) of the solution?

Calculating Molarity 1) 4.0 g NaOH x 1 mole NaOH = 0.10 mole NaOH 40.0 g NaOH 2) 500. mL x 1 L _ = L 1000 mL mole NaOH = 0.20 mole NaOH L

Learning Check M1 A KOH solution with a volume of 400 mL contains 2 mole KOH. What is the molarity of the solution? Drano

Solution M1 A KOH solution with a volume of 400 mL contains 2 moles of KOH. What is the molarity of the solution? 2) 5 M M = 2 mole KOH = 5 M 0.4 L Drano

Learning Check M2 A glucose solution with a volume of 2.0 L contains 72 g glucose (C 6 H 12 O 6 ). If glucose has a molar mass of 180. g/mole, what is the molarity of the glucose solution?

Solution M2 A glucose solution with a volume of 2.0 L contains 72 g glucose (C 6 H 12 O 6 ). If glucose has a molar mass of 180. g/mole, what is the molarity of the glucose solution? 1)72 g x 1 mole x 1 = 0.20 M 180. g 2.0 L

Learning Check M3 Stomach acid is a 0.10 M HCl solution. How many moles of HCl are in 1500 mL of stomach acid solution?

Solution M3 3) 1500 mL x 1 L = 1.5 L 1000 mL 1.5 L x 0.10 mole HCl = 0.15 mole HCl 1 L (Molarity factor)

Learning Check M4 How many grams of KCl are present in 2.5 L of 0.50 M KCl?

Solution M4 3) 2.5 L x 0.50 mole x 74.6 g KCl = 93 g KCl 1 L 1 mole KCl

Learning Check M6 How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?

Solution M6 2 ) 400. mL x 1 L = L 1000 mL L x 3.0 mole NaOH x 40.0 g NaOH 1 L 1 mole NaOH = 48 g NaOH