# concentration

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Concentration

### Solution Concentration:

Solution Concentration Read 281 – 283. Try questions 1 – 8 (show work) Concentration = quantity of solute quantity of solution (not solvent) There are 3 basic ways to express concentration: 1) percentages, 2) very low concentrations, and 3) molar concentrations 1) % concentration can be in V/V, W/W, or W/V Like most %s, V/V and W/W need to have the same units on top and bottom. W/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 H 2 O 2 /100 mL solution  3 g H 2 O 2 /100 g solution

### Solution Concentration:

Solution Concentration 2) Expressing concentrations in parts per million (ppm) requires the unit on top to be 1,000,000 times smaller than the unit on the bottom E.g. 1 mg/kg or  g/g Multiples of 1000 are expressed in this order  _, m_, _, k_ (“_” is the base unit) (pg.631) Notice that any units expressed as a volume must be referring to a water solution (1L = 1kg) For parts per billion (ppb), the top unit would have to be 1,000,000,000 times smaller 3) Molar concentration is the most commonly used in chemistry. Ensure that units are mol/L.

### PowerPoint Presentation:

Percentage concentration (V/V, W/V, W/W), very low concentration, molar concentration % V/V = 4.1 L / 55 L = 7.5% V/V % W/V = 16 g / 50 mL = 32% W/V % W/W = 1.7 g / 35.0 g = 4.9% W/W 8 ppm = 8 _ / 1 L, the units should be 1 million times smaller than 1L (or 1kg): 8ppm = 8 mg/L so the mass in 1 L is 8 mg. 3.2 mg/0.59 kg = 5. 4 24 mg/kg = 5.4 ppm a) ppb is 1000 times smaller than ppm b) 1 g/10 9 mL, 1 mg/1000 L, 1  g/L, 1 mg/kL, 1 mg/Mg, 1  g/kg 0.11 mol / 0.060 L = 1.8 mol/L

### More practice:

10 g / 260 g = 3.8 % W/W 30 mL / 280 mL = 11% V/V (in reality may be off) 8.0 g / 100 g = 8% W/W More practice What is the % W/W 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 % W/W if 8.0 g copper is added to enough zinc to produce 100 g of an alloy? Read 284 – 287. Do Q 11 – 17 (show work) 