Solutions, Chapter 16 (Unit 2) Mr. Samaniego Lawndale High School Sinkhole in Guatemala

California Standards Solutions 6. Solutions are homogeneous mixtures of two or more substances. As a basis for understanding this concept: a.Students know the definitions of solute and solvent. c. Students know temperature, pressure, and surface area affect the dissolving process. d. Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent composition.

solute vs solvent (6a) In a solution, the dissolving medium is the solvent, and the dissolved particles are the solute. A solvent dissolves the solute. The solute becomes dispersed in the solvent. Solutes and solvents can be solids, liquids, or gases. Examples of solutes and solvents : Salt water: water is the solvent and salt is the solute (aqueous solution). Air: at about 80% nitrogen and 19% oxygen; the nitrogen is the solvent and oxygen is one of the solutes.

Identify the solute/solvent Lemonade (lemon juice, water, sugar) Cookies (flour, chocolate chips, sugar) Mr. Samaniego’s Gold ring – Weighted at 70% Au and 30% Ag

16.1 Properties of Solutions 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. Saturated solution contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure.

Lab: Saturating H 2 O with NaCl Purpose: To discover the solubility of salt in water and calculate the concentration in two ways. Materials: beaker distilled H 2 O NaCl scooper balance stirrer (1 popsicle stick)

Lab: Saturating H 2 O with NaCl 1. How much salt can you dissolve in 25 mL of water? 2. Find the concentration in g/L and molarity. 3. Calculate % error g NaCl/100 gH 2 O Under 1 atm and 20 o C Or g NaCl/L H 2 O Or 6.14 M NaCl Percent error =

Data Beaker with 25 mL H2O ____ g (NO salt) Saturated solution _____ g (salt added) Salt added _____ g (difference)

Concentration There are four basic ways to calculate the concentration of a solution: molarity grams per liter parts per million percent composition (by mass)

Molarity Molarity: the number of moles of solute dissolved in one liter of solution. To calculate the molarity of a solution, divide the moles of solute by the volume of the solution. C = n/V Concentration (C): molarity (M) amount (n): # of moles Volume (v): liters (L)

Grams/liter One way of finding concentration is by dividing the mass in grams by the volume in liters.

Henry’s Law Henry’s Law: at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid.

Calculating Solubility If the solubility of a gas in water is 0.77 g/L at 3.5 atm of pressure, what is its solubility (in g/L) at 1.0 atm of pressure? (The temperature is held constant at 25 o C.)

Calculating the Molarity of a Solution Intravenous (IV) saline solutions are often administered to patients in the hospital. One saline solution contains 0.90 g NaCl in exactly 100 mL of solution. What is the molarity of the solution? Per Tab

Finding the Moles of Solute in a Solution Household laundry bleach is a dilute aqeous solution of sodium hypochlorite (NaClO). How many moles of solute are present in 1.5 L of 0.70 M NaClO?

Warm-up ( , ) 1.In a solution of coffee that has sugar, coffee brew, and creamer, which one is the solvent and solute portions? 2.If a solution of copper(I) nitrate has a solubility of 12.4 g/L at 123 kPa, what solubility will it have at 212 kPa? 3.Calculate the concentration in molarity of g of magnesium iodide dissolved in 255 mL. Solvent: brewed coffee; solute: sugar and creamer 21.4 g/L of copper(I) nitrate Per Tab 7.06 g/L MgI 2

Warm-up ( , ) 1.Describe the difference between a solvent and solute and what does it apply to, solids, liquids, or gases? 2.If a solution of potassium nitrate has a solubility of 35.3 g/L at 229 kPa, what solubility will it have at 515 kPa? 3.Calculate the concentration in molarity of 367 g of potassium oxide dissolved in 751 mL of solution g/L of KNO 3 Per Tab 5.19 M K 2 O

Percent Solutions Percent by mass can be written as the ratio of the mass of the solute to the mass of the solution. Percent by mass (% (m/m)) = x 100% mass of solute mass of solution

Assignments p. 477: 1-7 ( , ) p : 8-13 ( ) Lab Activity: Concentration (2-27, 2-28) p : ( , 2-28)

Concentration Problem Solving Finding molarity (M) from mass of solute 1.Find the # of moles of solute (use molar mass) 2.If volume is in mL, convert to liters (L) 3.Divide # of moles by volume 4.Answer is in molarity (M).

Practice on molarity 1. There are 13.4 g of K 2 SO 4 dissolved in 245 mL of solution. What is the molarity of this potassium sulfate solution? Per Tab M K 2 SO 4

Practice on molarity 2. Find the molarity of 1,250 mL solution when 116 g of NH 4 Cl are dissolved in it. Per Tab 1.73 M NH 4 Cl

Practice on molarity 3. What is the concentration (molarity) if 233 g of Mg 3 (PO 4 ) 2 are dissolved in 983 mL of water. Per Tab M Mg 3 (PO 4 ) 2

Practice on molarity 4. What is the concentration (molarity) if 673 g of LiMnO 4 are dissolved in 842 mL of water. Per Tab 6.35 M LiMnO 4

Practice on molarity 5. Find the concentration of sodium acetate if 162 g NaC 2 H 3 O 2 are dissolved in 1,570 mL of water. Per Tab 1.26 M NaC 2 H 3 O 2

Practice on molarity 6. Find the volume in mL of hydrogen phosphate if 162 g have a concentration of 3.19 M H 3 PO 4. Per Tab 518 mL H 3 PO 4

Practice on molarity 7. Find the volume in L of 6.93 M solution of 739 g of NH 4 Cl are dissolved in it. Per Tab 1.73 L NH 4 Cl

Practice on molarity 8. Find the volume in mL of 2.25 M solution of 1,670 g of Na 3 PO 4 are dissolved in it. Per Tab 1.73 L Na 3 PO 4

Warm-up (3-5-12, ) 1.Which solution is most concentrated: a) 2.4 M CaCl 2 b) 1.3 M CaCl 2 c) 4.2 M CaCl 2 2.What is the molar mass of K 2 CrO 4 ? 3.Calculate the number of grams in 0.5 mol of K 2 CrO 4. c) g Per Tab 97.1 g

Quiz: Solutions Ver. B 1.V. 2.More solvent 3.V. 4.Solvent: heavy cream solute: others g/L g/L BaCr 2 O M BaCr 2 O 7 Ver. A 1.V. 2.More solvent 3.V. 4.Solvent: ice cream solute: others g/L g/L SrSO M SrSO 3

Percent Solutions Percent by mass can be written as the ratio of the mass of the solute to the mass of the solution. Percent by mass (% (m/m)) = x 100% mass of solute mass of solution

Percent Solutions 1. Enough barium chloride dissolves in a solution to provide a 22.4 g solution. If 12.8 g of barium chloride were used, what is the percentage composition of barium chloride? 57.1 %

Percent Solutions 2. On the top of a mountain, it was discovered that 123 g of O 2 was found with 412 g of N 2. What was the percent composition of O 2 there? 23.0 %

Percent Solutions 3.The composition of masa (cornmeal) was found to have 2.0 g sodium azide, 725 g water and 12 g starch. What was the percent composition of sodium azide? 0.27 %

Parts Per Million (ppm) Parts Per Million (ppm) can be written as the ratio of the mass of the solute to the mass of the solution multiplied by Parts Per Million (PPM) = x 10 6 mass of solute mass of solution Note: 1 L of water = 1,000 g; density of water = 1g/mL also, 1 g = 1,000 mg

Parts Per Million 4. A company selling bottled water had levels of Ni in it that were tested and found to be mg in a solution of water of 75,000 mg. What was the concentration in ppm? 0.32 ppm

Parts Per Million 5. How many parts per million of CO 2 gas are found dissolved in water if 72.3 mg are measured in 445 L of water? ppm

*Parts Per Million (ppm) Parts Per Million (ppm) can also be expressed as the ratio of the mass of the solute in mg to the volume of the solution multiplied in L. Parts Per Million (PPM) = mass of solute in mg volume of solution in L *Adapted from test bank question in Data Director.

Strategies in Problem Solving: Solution Problems

Strategies in Problem Solving: Solution Problems IdentifyConversionsCalculator known/ uknown values must include proper units!!! use LOGIC (You can do it!) must have unit agreement divide across bottom multiply across top