Concentration Units and Comparison of Concentration Units (original) (raw)

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 = í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí± í µí± í µí±í µí±í µí± í µí± 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 í µí±í µí± í µí°¾í µí°¾í µí°¾í µí°¾í µí±í µí± (0.892 í µí±í µí± í µí°¾í µí°¾í µí°¾í µí°¾í µí±í µí±+54.6 í µí±í µí± í µí°»í µí°»2í µí±í µí±) x 100 percent by mass = 1.61 % (b) Percent by Volume (i) Formula: percent by volume = í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±£í µí±£í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí± í µí± í µí±í µí±í µí± í µí± 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 í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± (111.0 í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±£í µí±£í µí±í µí±í µí± í µí± í µí±í µí± +5.24 í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí±) x 100% percent by volume = 0.0450791466 x 100% percent by volume = 4.51% (c) Mass/Volume Percent (i) Formula: percent by volume = í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±£í µí±£í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí± í µí± í µí±í µí±í µí± í µí± 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 í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± (111.0 í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±£í µí±£í µí±í µí±í µí± í µí± í µí±í µí± +5.24 í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí±í µí±í µí±) x 100% percent by volume = 0.0520 x 100% percent by volume = 5.205%

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Concentration Units and Comparison of Concentration Units (original) (raw)

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