1. Concentration Calculations Answers

2. 1. What is the formula for calculating molarity? M = moles solute L of solution

3. 2. What is the formula for calculating % by mass? %mass = g of solute x 100% total g of solution 3. What is the formula for calculating % by volume? %volume= L of solute x 100% total L of solution

4. 4. What is the %volume of 2L of sodium bicarbonate dissolved in 5L of water? % volume = 2 x 100% 7 (remember this is total volume) = 28.6%

5. 5. What is the %mass of a solution with 20g NaCl dissolved in 600g of water? % mass= 20 x 100% 620 (remember this is total mass) = 3.2%

6. 6. What is the % mass of 20 g KCl in 600 mL of water? a.What is the mass of 600 mL of water? Remember – density of water is 1g/1mL so 600 mL = 600 g b. What is the % mass of the solution? % mass= 20 x 100% 620 (remember this is total mass) = 3.2%

7. 7. You have a 5% dextrose solution. If you dissolved 50 mL of dextrose, what is the volume of the water? %volume= mL of solute x 100% total mL of solution 5 = 50 x 100 5 = 5000 50 + x50 + x 5 (50 + x) = 5000250 + 5x = 5000 5x = 4750x = 950 mL

8. 8. You have a 3.5% by mass bleach solution. If you have 1000 g of the solution, how much solute is dissolved? %mass= g of solute x 100% total g of solution 3.5 = x x 100 3.5 = 100x 10001000 100 x = 3.5 (1000)100x= 3500 x = 35g

9. 9. A 0.100 L solution has 5.1 g of NaCl. a. How many moles are in 5.1 g NaCl? ( mw of NaCl = 58 g) 5.1g NaCl 1 mole NaCl = 0.09 moles NaCl 58g NaCl b. What is the molarity of the solution? M = moles soluteM = 0.09 moles = 0.9 M L of solution 0.1 L

10. 10. A solution is made with 20g of glucose and 1.5L of solution. (MW glucose = 180g) a. How many moles of glucose do you have? 20g glucose 1 mole glucose = 0.1 moles glucose 180g glucose b. What is the molarity of the solution? M = moles soluteM = 0.1moles = 0.07 M L of solution 1.5 L

11. 11. A 0.5M KBr solution has a volume of 5L. a. How many moles are used to make the solution? M = moles solute0.5 = x moles L of solution 5 L X moles = 0.5 (5) = 2.5 moles b. What is the mass of the solute? (mw KBr = 119 g) 2.5moles KBr 119 g KBr = 297.5 g KBr 1 moles KBr

12. 13. If 50mL of acetone is mixed with 450 mL of water, what is the % volume? %volume= L of solute x 100% total L of solution % = 50 x 100% = 10% 500

13. 14. A bottle of hydrogen peroxide is labeled at 3%. If you pour out 50mL of the solution, what volume is actually hydrogen peroxide? %volume= L of solute x 100% total L of solution 3 = x x 100% 3 = 100x50 100x = 3(50)100x = 150x = 1.5 mL

14. 15. A contaminant in the air measured at 2 ppm. Your family is freaking out. How would you explain what 2 ppm means to them? There are 2 molecules of contaminant per 1 million molecules of air.