Concentration

Solution Concentration Concentration = quantity of solute quantity of solution (not solvent) The main way we express concentration is using % % concentration can be in V/V, M/M, or M/V V/V and M/M have same units on top and bottom. M/V is sort of in the same units; V is mostly water and water’s density is 1 g/mL or 1 kg/L 3 g H2O/100 mL solution  3 g H2O/100 g solution

Mass of Solution = Mass of Solute + Mass of Solvent Mass Percent or Percent by Mass Parts Per Hundred % = grams of solute per 100 g of solution 5.0% NaCl has 5.0 g of NaCl in every 100 g of solution Mass of Solution = Mass of Solute + Mass of Solvent Divide the mass of solute by the mass of solution x by 100 Percentage concentration (V/V, M/V, M/M), % V/V = 4.1 L / 55 L = 7.5% V/V % M/V = 16 g / 50 mL = 32% M/V % M/M = 1.7 g / 35.0 g = 4.9% M/M

Mass Percent By mass, the percent of the solution that is solute = Mass of solute______ x 100 Mass of solute + mass of solvent 1. A 135g of seawater is evaporated, 4.73 g of salt is left. Calculate the mass % of the salt in the seawater.   2. A 40% solution of formaldehyde is used to preserve animals. What mass of water must be added to 425 g of solid formaldehyde to make this solution?

30 mL / 280 mL = 11% V/V (in reality may be off) More practice What is the % M/M of copper in an alloy when 10 g of Cu is mixed with 250 g of Zn? What is approximate % V/V if 30 mL of pure ethanol is added to 250 mL of water? What is the % M/M if 8.0 g copper is added to enough zinc to produce 100 g of an alloy 10 g / 260 g = 3.8 % M/M 30 mL / 280 mL = 11% V/V (in reality may be off) 8.0 g / 100 g = 8% M/M