SH1726 02 Handout 1 *Property of STI Page 1 of 3 Concentration Units and Comparison of Concentration Units I. Concentration Units Quantitative study of a solution requires knowing its concentration, the amount of solute present in a given amount of solution. Chemists use different types of concentration units, each having its own advantages and limitations. 1. Types of Concentration Units (a) Percent by Mass (i) Formula: percent by mass =       x 100% (ii) Unit: unitless, because it is a ratio of two similar (iii)Problem: A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is the percent by mass of KCl in the solution? (iv) Solution: percent by mass = 0.892   (0.892  +54.6  2) x 100 percent by mass = 1.61 % (b) Percent by Volume (i) Formula: percent by volume =       x 100% (ii) Unit: unitless (iii)Problem: In a solution, there is 111.0 mL (110.605 g) of solvent and 5.24 mL (6.0508 g) of solute. Find its percent by volume. (iv) Solution: percent by volume = 5.24   (111.0   +5.24  ) x 100% percent by volume = 0.0450791466 x 100% percent by volume = 4.51% (c) Mass/Volume Percent (i) Formula: percent by volume =       x 100% (ii) Unit: unitless (iii)Problem: In a solution, there is 111.0 mL (110.605 g) of solvent and 5.24 mL (6.0508 g) of solute. Find its percent by mass/volume percentage. (iv) Solution: percent by volume = 6.0508   (111.0   +5.24  ) x 100% percent by volume = 0.0520 x 100% percent by volume = 5.205%