Chemistry 20

 concentration: a ratio that compares the quantity of solute to the quantity of solution  A dilute solution has a relatively small quantity of solute per unit volume of solution compared to a concentrated solution.

 A solution in which a pure liquid is dissolved in water may have a percentage volume by volume (% V/V) reported.  Ex. Vinegar is labeled 5% V/V acetic acid

 What is the concentration (in % V/V) of a solution in which 225 mL of pure sulfuric acid is found in 2.00 L of solution?

 An ammonia solution in a beaker is labeled 13.0 % V/V. What volume of pure ammonia has been dissolved in making 350 mL of this solution?

 Another common concentration ratio used for consumer products is “percentage weight by volume” or % W/V  Ex. Hydrogen peroxide is labeled 3% W/V

 What is the concentration (in % W/V) of a solution in which 74.0 g of sugar is found in 1500 mL of solution?

 A sodium chloride solution in a beaker is labeled 3.5 % W/V. Calculate the volume of this solution that contains 750 mg of dissolved solute.

 A third concentration unit is the “percentage weight by weight”, or % W/W.  Ex. A stainless steel alloy contains 11.5% W/W chromium.

 A sterling silver ring has a mass of 12.0 g and contains 11.1 g of pure silver. What is the concentration (in % W/W) of silver in the ring?

 A bronze medal is 88% W/W copper and 12% W/W tin. What mass of each metal is present (to the tenth) in a 282 g bronze medal?

 In solutions found in the environment (ex. iron in well water), we often find very low concentrations.  Very small concentrations are often expressed in parts per million (ppm) or even parts per billion (ppb).

 At these very low concentrations, the solution is extremely dilute. Dilute aqueous solutions are assumed to have the same density as pure water (exactly 1 g/mL).

 Well water is not recommended for drinking if dissolved lead has a concentration of 15 ppb or higher. What is the maximum mass of lead that can be dissolved in 20.0 L of water that is safe to drink?

 A sample of hard water contains 300 ppm calcium carbonate. What mass of calcium carbonate will be found in 500 mL of hard water?

 m = g

 A mountain spring water source is analyzed to contain 485 ppb of dissolved iron. What volume of spring water must be collected in order to contain 1.00 g of dissolved iron?

 Concentration Practice Problems  Solubility Graphing Assignment due tomorrow!