Name: _________________ Measuring

ConcentrationsMolarity

Explain the following statement:“A measure of the molarity of a solution is more meaningful than knowing

whether a solution is dilute or concentrated.”

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1. You have 3.50 L of solution that contains 90.0 grams of sodium chloride, NaCl. What is the molarity of the solution?

2. A salt solution has a volume of 250mL and contains 0.70 mol of KNO3. What is the molarity of the solution?

3. You have 0.8 L of a 0.5 M HNO3 solution. How many moles of HNO3 does this solution contain?

4. How many grams of solute are present in 1.5 L of 0.20M Na2SO4?

Formula:

5. You have an aqueous solution that has a volume of 2.0 L and contains 36.0 g of

glucose. If the gram formula mass (molar mass) of glucose is 180.0g, what is the molarity of your solution?

6. How many moles of solute are in 375 mL of 2.0 M CaCl2?

How many grams of CaCl2 does this solution represent?

Thought Question:If you were given the following:CaCl2(s), electronic scale, weighing boat, distilled water, and a 100 mL graduated cylinder.

Describe in detailed steps, how you would prepare a 50 mL of a .35M solution of CaCl2(aq).

Name: ________________________ Changing

Concentrations Dilutions

Molarity By DilutionAcids are usually acquired from chemical supply houses in concentrated form. These acids are diluted to the desired concentration by adding distilled water.

1. How much concentrated 18 M sulfuric acid is needed to prepare 250 mL of a 6.0 M solution?

2. How much concentrated 12 M hydrochloric acid is needed to prepare 100 mL of a 2.0 M solution?

3. To what volume should 25 mL of 15 M nitric acid be diluted to prepare a 3.0 M solution?

4. To how much water should 50.0 mL of 12 M hydrochloric acid be added to produce a 4.0 M solution?

Formula:

5. To how much water should 100.0 mL of 18 M sulfuric acid be added to prepare 1.5 M solution?

Name: ________________________Solutions Containing Very Little

Solute Parts Per Million

1. A chemical analysis shows that there are .0022g of lead in exactly 500 grams of a water sample. Convert this measurement to ppm.

2. An 870.0 grams river water sample contains 7.5 mg of cadmium. Express the concentration of cadmium in ppm.

3. An aqueous solution has 0.0070 gram of oxygen dissolved in 1000. grams of water. Calculate the dissolved oxygen concentration of this solution in parts per million.

Formula:

4. If 0.025 gram of Pb(NO3)2 is dissolved in 100. grams of H2O, what is the concentration of the resulting solution, in parts per million?

(1) 2.5 × 10–4 ppm    (2) 2.5 ppm      (3) 250 ppm     (4) 4.0 × 103 ppm

6. What is the total mass of solute in 1000. grams of a solution having a concentration of 5 parts per million?

(1) 0.005 g     (2) 0.05 g    (3) 0.5 g    (4) 5 g

Real World Connection:Clean drinking water is scarce in Bangladesh, one of the poorest countries in the world. Ravaged frequently by floods, the surface waters that supplied the drinking water for most of the country until 35 years ago were often contaminated by disease-causing microorganisms. During the 1970’s, UNICEF and the World Bank provided funds for the construction of tubewells to provide a consistent supply of clean drinking water. The project involved constructing hundreds of thousands of tubewells; a well within 100 m of every family.Much to everyone’s surprise, the wells brought a new risk: chronic arsenic poisoning. Arsenic occurs naturally in mineral formations of the region, and it now contaminates the water collecting in many of the wells. Skin pigmentation, warts, diarrhea, and ulcers characterize the initial stages of arsenic poisoning.

If 0.076 gram of arsenic is dissolved in 600. grams of H2O, what is the concentration of the resulting solution, in parts per million?

Name: _______________________

Another Way of Measuring Concentration

Mass Percent of a Solution

1. A student dissolves 25.0 grams of glucose in 475 grams of water. What is the percent concentration of the glucose in solution?

2. A 4 g sugar cube (Sucrose: C12H22O11) is dissolved in 350 grams of water. What is the percent composition by mass of the sugar solution?

3. How would you prepare 400. g of a 2.50% solution of sodium chloride?

Formula:

4. Calculate the mass percent of a solution containing 27.5 g of ethanol (C2H6O) and 175 mL of H2O. Assume that the density of water is 1.00 g/ mL)