Measures of Concentration Concentration The amount of solute

  • Slides: 27
Download presentation
Measures of Concentration

Measures of Concentration

Concentration • The amount of solute that is dissolved in a solvent • A

Concentration • The amount of solute that is dissolved in a solvent • A precise quantitative measurement § Terms such as “diluted” and “concentrated” are too vague.

Concentration amount of solute amt. of solution (or solvent)

Concentration amount of solute amt. of solution (or solvent)

Percent by Mass g solute × 100% g solution v. Useful only when comparing

Percent by Mass g solute × 100% g solution v. Useful only when comparing different concentrations of the same solution

Sample Problem 1 If 5. 81 g of salt is dissolved in water to

Sample Problem 1 If 5. 81 g of salt is dissolved in water to make 56. 3 g of solution, what is the percent by mass? 5. 81 g solute × 100% = 10. 3% 56. 3 g solution

Question If 10 grams of sugar is added to 90 grams of water, what

Question If 10 grams of sugar is added to 90 grams of water, what is the percent by mass? 1. 2. 3. 4. 10% 11% 5% 20%

Question If 10 grams of sugar is added to 90 grams of water, what

Question If 10 grams of sugar is added to 90 grams of water, what is the percent by mass? 1. 10% 10 g sugar = 10% sugar soln 100 g total

Question When 25 g of salt is dissolved to make 125 g solution, what

Question When 25 g of salt is dissolved to make 125 g solution, what is the percent by mass? 1. 2. 3. 4. 10% 20% 16. 7% 25%

Question When 25 g of salt is dissolved to make 125 g solution, what

Question When 25 g of salt is dissolved to make 125 g solution, what is the percent by mass? 2. 20% 25 g salt = 20% solution 125 g total

Percent by Volume volume of solute × 100% volume of solution

Percent by Volume volume of solute × 100% volume of solution

Molarity molarity (M) = mol solute L solution

Molarity molarity (M) = mol solute L solution

Sample Problem 2 Dissolving 345 g of HCl to make 3. 75 L of

Sample Problem 2 Dissolving 345 g of HCl to make 3. 75 L of solution results in what molarity? 345 g HCl 1 mol HCl 3. 75 L soln 36. 5 g HCl = 2. 52 M HCl

Question If 2. 9 moles Na. Cl is dissolved to make 3. 8 L

Question If 2. 9 moles Na. Cl is dissolved to make 3. 8 L of solution, what is the M? 1. 2. 3. 4. 2. 5 M Na. Cl 5. 8 M Na. Cl 1. 3 M Na. Cl 0. 76 M Na. Cl

Question If 2. 9 moles Na. Cl is dissolved to make 3. 8 L

Question If 2. 9 moles Na. Cl is dissolved to make 3. 8 L of solution, what is the M? 2. 9 mol Na. Cl = 0. 76 M Na. Cl 3. 8 L soln 4. 0. 76 M Na. Cl

Question If 200 g Na 2 SO 4 is added to make 3. 5

Question If 200 g Na 2 SO 4 is added to make 3. 5 L of solution, what is the M? 1. 2. 3. 4. 1. 8 M Na 2 SO 4 0. 40 M Na 2 SO 4 2. 6 M Na 2 SO 4 2. 2 M Na 2 SO 4

Question If 200 g Na 2 SO 4 is added to make 3. 5

Question If 200 g Na 2 SO 4 is added to make 3. 5 L of solution, what is the M? 2. 0. 40 M Na 2 SO 4 200 g Na 2 SO 4 1 mol Na 2 SO 4 3. 5 L soln 142 g Na 2 SO 4 = 0. 40 M Na 2 SO 4 soln

Sample Problem 3 You have 0. 6 L of a 0. 5 M HCl

Sample Problem 3 You have 0. 6 L of a 0. 5 M HCl solution. How many moles of HCl does this solution contain? Solution: The M value gives you the number of mol that are in 1 L of soln. You can use this ratio as a conversion factor.

Sample Problem 3 0. 6 L soln 0. 5 mol HCl 1 L soln

Sample Problem 3 0. 6 L soln 0. 5 mol HCl 1 L soln = 0. 3 mol HCl

Sample Problem 4 A chemical reaction requires 0. 180 mol of silver nitrate (Ag.

Sample Problem 4 A chemical reaction requires 0. 180 mol of silver nitrate (Ag. NO 3). How many m. L of a 0. 800 M solution should be added to the reaction vessel to provide this amount?

Sample Problem 4 Solution: Since M means moles of solute per liter of solution,

Sample Problem 4 Solution: Since M means moles of solute per liter of solution, we can rewrite the concentration as 0. 800 mol Ag. NO 3/1 L of solution and use its inverse as a conversion factor.

Sample Problem 4 0. 180 mol Ag. NO 3 1 L soln 1000 m.

Sample Problem 4 0. 180 mol Ag. NO 3 1 L soln 1000 m. L 0. 800 mol Ag. NO 3 1 L = 225 m. L soln

Molality molality (m) = mol solute kg solvent

Molality molality (m) = mol solute kg solvent

Sample Problem 5 If 271 g of H 2 SO 4 is added to

Sample Problem 5 If 271 g of H 2 SO 4 is added to 724 g of water, what is the molality of the solution? 271 g acid 1 mol acid 0. 724 kg H 2 O 98 g acid = 3. 82 m acid

Question What is the molality of a solution formed by adding 1. 25 mol

Question What is the molality of a solution formed by adding 1. 25 mol of Li. Cl to 2. 8 kg of water? 1. 2. 24 m Li. Cl 2. 4. 05 m Li. Cl 3. 0. 45 m Li. Cl 4. 1. 55 m Li. Cl 5. 9. 87 m Li. Cl

Question What is the molality of a solution formed by adding 1. 25 mol

Question What is the molality of a solution formed by adding 1. 25 mol of Li. Cl to 2. 8 kg of water? 3. 0. 45 m Li. Cl 1. 25 mol Li. Cl = 0. 45 m Li. Cl soln 2. 8 kg H 2 O

Question When 136 g of Na. Cl is added to 780 g of water,

Question When 136 g of Na. Cl is added to 780 g of water, what is the molality? 1. 0. 17 m Na. Cl 2. 2. 99 m Na. Cl 3. 0. 00298 m Na. Cl 4. 5. 73 m Na. Cl 5. 8. 13 m Na. Cl

Question When 136 g of Na. Cl is added to 780 g of water,

Question When 136 g of Na. Cl is added to 780 g of water, what is the molality? 2. 2. 99 m Na. Cl 136 g Na. Cl 1 mol Na. Cl. 780 kg H 2 O 58. 4 g Na. Cl = 2. 99 m Na. Cl soln