p39 solutions

Exercises (Mass/Volume Percent and g/L)

1.         5.0 grams of sugar are dissolved in 150 ml of aqueous solution. What is the m/V percent of sugar in the solution?

5/(150) * 100 % = 3.3 %

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2.         A 200 ml solution of alcohol contains 20 g of alcohol. What is the mass/V percent of alcohol?

(20)/200 * 100 % = 10.0%

3.         How many grams of NaBr are needed to make 50 ml of a 5.0 m/V % solution?

50 ml (50g/100 ml) = 2.5 g

4.         You are using 150 mL of ether as a solvent. What mass of sulfanilamide crystals should be added to create a 10m/V% solution.

x /( 150ml) = 10g/100ml           y

x = 15 = 15g of sulphanilamide

5.         How many grams of LiOH are needed to make 25 ml of a 4.0 m/V % solution?

0.04(25) = 1.0 g

6.         What mass of NaF must be mixed with 25 mL of water to create a 3. 5 m/V% solution.

x/( 25) = 0.035

x = 0.875 g

7.        An 800 ml solution of Kool Aid (mass 20 g) contains 780 g of water. What is the m/V percent of solute in this solution?

(20g)/800 * 100% = 2.5%

8.        What is the m/V percent of a solution created by adding 10 ml of olive oil (density 0.8g/ml) to 90 ml of vegetable oil?

mass of olive oil = 8g/ml*10ml = 8 g

8/(10+90)* 100% = 8 %

9.        If a 4000 ml solution of salt contains 40 g of salt, what is its m/V percent?

40/4000 *100% = 1.0%

Concentration in g/L

1.                  Find the concentration in g/L for each of the following:

a.                   20 g of NaCl dissolved in 500 L of solution

20g/500 L = 0.04 g/L

b.                  2.8 g of NaBr dissolved in 200 mL of solution

2.8g/0.200L = 14g/L

c.                   200 mg of KCl dissolved in 75 mL of solution

0.200g/0.075L = 2.67 g/L Note that 1 mg/ml = 1 g/L

2.                  How many grams of Br2 are needed to make 250 mL of a 4.5 g/L solution?

Mass = CV

m = 4.5 g/L (0.250 L) = 1.1 g

3.                  How many grams of HCl are needed to make 500 mL of a 2 g/L solution?

Mass = CV

m =  2 g/L (0.500L) = 1.0 g

4.                  How many grams of LIF are needed to make 2.0 L of a 5 g/L solution?

m = 10 g

5. What volume is needed to create a 2.0 g/L solution from dissolving 6.0 g of salt?

m = CV

6 = 2V

V = 3.0 L

6.                  Step by step, explain how you would actually prepare 2.0 L of a 5 g/L solution of NaCl in the lab.

1.                  Using a balance, weigh out 10.0 g of NaCl crystals.

2.                  Dissolve in less than 2.0 L in a beaker.