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1 Block 4 Molarity Packet Work List 1. /10 Cover / Vocabulary 2. /10 WCW 3. /10 Notes: Molarity # /10 Molarity: Concentration Solutions # /10 Molarity Worksheet 6. /10 Solution Concentration Worksheet Last, First Period, Date 7. /10 Determining Molarity Lab done on test day Objective Students must be able to Define and understand concentration. Calculate concentration using grams per liter. Calculate concentration using molarity. California State Standards Chemistry 6d- Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent composition. Chemistry 6e*- Students know the relationship between the molarity of a solute in a solution and the solution s depressed freezing point or elevated boiling point College and Career Readiness Anchor Standards for Reading Key ideas and Details-General #2 Determine central ideas or themes of a text and analyze their development; summarize the key supporting details and ideas. Science Grade Specific 11th-12th Determine the central ideas or conclusions of a text; summarize complex concepts, processes, or information presented in a text by paraphrasing them in simpler but accurate terms. Focus Questions Determine the molarity, parts per million, grams per liter and percent composition of an aqueous solution containing 40.0g of glucose (C 6 H 12 O 6 ) in 2 L of solution? How can I use solution concentration to determine Stoichiometric ratios? What are the different types of solution concentration units used for? Vocabulary on the back Concentration, dilute solution, concentrated solution, Molarity (M)

2 Vocabulary 1. Concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent. 2. Dilute solution is one that contains a small amount of solute. 3. Concentrated solution contains a large amount of solute. In chemistry, the most important unit of concentration is molarity. 4. Molarity (M) is the number of moles of solute dissolved in one liter of solution 5. Solute - The substance that dissolves or seems to disappear 6. Solvent - The substance that dissolves the solute 7. Solution the total of all solutes and solvents 8. Precipitate the material that falls out of Solutions site for notes pdf chapter reading

3 WCW Warm-up 9/24 wed odd 9/26 fri even Molarity is an expression of concentration with units of moles per liter M = mol / L mol = M*L L = mol / M Critical thinking none Wrap-up none Warm-up 9/29 mon odd 9/30 tue even Find the molar mass of NaOH Then convert to 5 moles. Find the molarity of 5 moles of NaOH in 2000ml. Critical thinking What do you call a solution that uses water as the solvent? Describe Hygroscopic. Wrap-up none Warm-up 10/1 wed odd 10/2 thu even Hygroscopic means to absorb or take in water from the atmosphere. What layer of the atmosphere do we live in? Critical thinking Under current rules MLB, baseball is between 5 and 5.25 ounces that is 142g to 149 g calculate the conversion factor. (oz/g) Wrap-up Problem #1 Find the Molarity of the solution that contains 93.7 grams of KNO3 in enough water to make cm3 of solution cm 3 = 250mL 2. calc mol mass of KNO3 = ( (16)) = Divide 93.7 g KNO3 by 101 = mol 4. change ml to L 5. divide thirds ans the mol by L 0.927/0.25 = problem #2... Calculate the number of moles a solution has when the Molarity is 0.5 and the volume is 750ml. (0.75)(0.5) = (101) = 37.8

4 Notes: Molarity Unit of Solution concentration Molarity (M) = moles of solute / Liters of Solution M = mol/l Find the molarity of a solution that contains 49.3 grams of NaCl in enough water to make ml of Solution. (49.3 g NaCl) * (1mol NaCl /58.5gNaCl) = mol/l =M = mol / 0.500L = 1.69 mol/l How many grams are needed to make 50.0ml of a 0.250M NaCl solution? mol = M * L = (0.25 M NaCl ) * (0.05L) = mol * (58.5 g NaCl / 1mol NaCl) = 0.731g NaCl How many grams are needed to make 2.5L of a 0.05 M NaCl solution? mol = M * L = (2.5 L ) * (0.05M) = mol * (58.5 g NaCl / 1mol NaCl) = 7.31g NaCl How would you prepare 100ml of 0.25M KNO3 solution? mol = M * L = (0.25M)(0.100L) = mol * (101.1 g KNO 3 /1molKNO 3 ) = 2.5 g KNO 3 How many grams of KOH are required to make 250.ml of a ^.om solution of KOH? 6.o M = 6 mol / L 0.250L * (6 mol/l) = 1.5 mol * (56g KOH /mol ) = 84g KOH More notes from web page

5 Molarity: Concentration Solutions # A solution has a volume of 2.0 L and contains 36.0 g of glucose (C 6 H 12 O 6 ). If the molar mass of glucose is 180 g/mol, what is the molarity of the solution? 36g / 180g/1mol = 0.2 mol 0.2 mol/2l = M = 0.1molarity 9. A solution has a volume of 250 ml and contains 0.70 mol NaCl. What is its molarity? M= 0.7mol / 0.25 L = 2.8 molarity 10. How many moles of ammonium nitrate are in 335 ml of 0.425M NH 4 N0 3? mol = 0.425M (.335L) = 0.14mol 11. How many moles of solute are in 250 ml of 2.0MCaCL? How many grams of CaCl, is this? mol = 2.0M (0.250L) =.5 mol 0.5mol (75g/1mol) = 37.5 g 12. How many milliliters of a solution of 4.00M KI are needed to prepare ml of 0.760M KI? 4M = 0.76 M 1000Mml = 0.76M X or X = ml or 1.3L X 250ml 13. How could you prepare 250 ml of 0.20M NaCl using only a solution of l.om NaCl and water? 1M = 0.2M 250Mml = 0.2M X or X = 1250ml or 1.25L X 250ml 14. If 10 ml of propanone (or acetone (C 3 H 6 O)) is diluted with water to a total solution volume of 200 ml, what is the percent by volume of propanone in the solution? 10ml/200ml = 1/20 = 0.05 or 5% 15. A bottle of the antiseptic hydrogen peroxide (H 2 O 2 ) is labeled 3.0% (v/v). How many ml H 2 O 2 are in a mL bottle of this solution? X/400ml = 3% X = 400ml (0.03) = 12ml 16. How do you calculate the molarity of a solution? Molarity of a solution = mol of solute / Liters of solution 17. Compare the number of moles of solute before dilution with the number of moles of solute after dilution. moles are the same the liters change, therefore the molarity decreases 18. What are two ways of expressing the concentration of a solution as a percent? The parts of solute / 100 parts of solution. The fraction of a solute in a solution multiplied by Calculate the molarity of a solution containing 400 g CuS0 4 in 4.00 L of solution. 400g CuSO4 * (1mol CuSO 4 / g CuSO 4 ) = mol CuSO 4 M= mol / L M = (2.475 mol CuSO4) / (4.00 L) M = mol/l

6 20. How many moles of solute are present in 50.0 ml of 0.20M KNO 3? # of moles = molarity (# of L) (.2 ) (.05) = ml = 0.05 L 21. How many milliliters of a stock solution of 2.00M KN03 would you need to prepare ml of 0.150MKNO 3? mol / L ( L) = mol calculate the amount of 2.00 M KNO3 that will give you mol: mol * (1 L /2 mol) = L L = 7.5 ml 22. What is the concentration, in percent (v/v), of a solution containing 50 ml of diethyl ether (C 4 H 10 O) in 2.5 L of solution? volume of ether = 50 ml total volume = 2.5 L which is the same as 2500 ml 50 ml / 2500 ml * 100 = 2 % 23. How many grams of K 2 S0 4 would you need to prepare 1500 g of 5.0% K 2 SO 4 (m/m) solution? weight percent of a solution = (mass of solute)/(mass of solution) The solution is 5.0% K2SO4 and has a total mass of 1500 g. mass K2SO4 = (0.050)(1500 g) = 75 g K2SO4 mass H2O = 1500 g - 75 g = 1425 g H2O So, take 75 g K2SO4 (anhydrous) and dissolve it in 1425 g of distilled or deionized H2O. This will prepare your solution. wt % = [(75 g)/(1500 g)]*100% = 5.0%

7 Molarity Worksheet Show work and units 1. What is the definition and units of molarity? M=mol/L 2. Why do chemists use molarity to express concentration of solutions, rather than percent by volume or percent (mass/volume)? Volume because we divide by Liters Volumen porque dividimos por Litros 3. Calculate the molarity of moles NaHCO3 in ml of solution mol / 1.5L = 4. What is the molar concentration of 1.0 mol of KCl dissolved in 750. ml of solution? 1.0 mol / L = 5. Calculate the molarity of grams of NaCl in 2.0 liters of solution. Na= 23g and Cl = 35g NaCl = 58g 29.25g / 58 g = mol mol / 2L = 6. Calculate the molarity of 34.2 grams of sugar, C12H22O11 in 500. ml of solution. C = 12g H = 1g O =16g = 342g 34.2/342 = 0.1 mol / 0.5 L = Calculate the number of moles of NaCl contained in 0.500L of a 1.5M solution. M*L = 1.5M * 0.5L = 0.75 mol 8. How many grams of NaCl are contained in the solution discussed in problem #7? 0.75 mole* 58g = 9. Calculate the number of moles of NaOH contained in 250. ml of a 0.05M solution. 40 g / mol 0.05 (0.25)= 10. How many grams and moles of solute are there in 250. ml of a 0.10M CaCl2 solution? 0.10(.250) = mol * (110g/mol)= Answers: 3).040M (2sf) 4) 1.3M (2sf) 5) 0.25M (2sf) 6).200M (3sf) 7).75mole (2sf) 8) 44g (2sf) 9) 0.01mol (1sf) 10) 0.025mole and 2.8 g CaCl2 (2sf)

8 Molarity Worksheet Find the molarity of the following solutions: Na = 23 g Cl = 35 g Li = 7 g S = 32 g O = 16 g Pb = 207 C = 12 g H = 1 g 1) 0.5 moles of sodium chloride is dissolved to make 0.05 liters of solution. M=mol/L = 0.5 mol / 0.05 L = 2) 0.5 grams of sodium chloride is dissolved to make 0.05 liters of solution. M=mol/L = (0.5g )(1mol/58g) / 0.05 = ) 0.5 grams of sodium chloride is dissolved to make 0.05 ml of solution. M=mol/L = (0.5g )(1mol/58g) / = ) 734 grams of lithium sulfate (Li 2 SO 4 ) are dissolved to make 2500 ml of solution. M=mol/L = (734g)(1mol/110g) / (2.5L) = ) 6.7 x 10-2 grams of Pb(C 2 H 3 O 2 ) 4 are dissolved to make 3.5 ml of solution. M= mol/l = (6.7 x 10-2 g)(1mol/443g) / L = ) I have two solutions. In the first solution, 1.0 moles of sodium chloride is dissolved to make 1.0 liters of solution. In the second one, 1.0 moles of sodium chloride is added to 1.0 liters of water. Is the molarity of each solution the same? Explain your answer. The equation for molarity states that the molarity of a solution is equal to the number of moles of solute divided by the number of liters of solution. In the first equation, the molarity will clearly be equal to 1.0 M, because there are 1.0 moles of NaCl and a solution volume of 1.0 L. In the second solution, the molarity will be different, because the solution volume will be greater than 1.0 liters. Why? If you already have 1.0 L of water and add 1.0 moles of salt to it, it will overflow, right? This is because the volume will be (roughly) equal to the volume of the water plus the volume of the salt, which will be greater than 1.0 L. It is for this reason that when you make a solution, you always dissolve the solute in only a little bit of water and then add water to make your final volume.

9 Solution Concentration b, d, b, d, 7.54g, 85mL, M=mol/L, mol, Liters, 85/1000

10 Solution Concentration 11. What quantity must be used to convert the mass of the solute given in the problem to the amount of solute needed to calculate molarity? Molar mass 12. Write the expression used to calculate the amount of solute mol = M*L 13 Calculate the molarity of the solution. Show work. 7.54g (1mol/126g) = 0.05 mol 0.05 mol/0.085l = 0.7 M 14. How does molarity differ from molality? 15. Calculate the molality of a solution of 15.4g sodium bromide NaBr dissolved in 125 g of water. Show work 16. What is a mole fraction? Ratio of mole to mole that can be used as a conversion factor 17. Calculate the mole fraction of HCl in an aqueous solution that contains 33.6% HCl by mass. Show all work.