Concentration

The most common methods of expressing the concentrations of chemicals using drugs in solutions or mixtures are: weight per unit of weight or weight/weight or w/w volume per unit of volume or volume/volume or vv weight per unit of volume or weight/volume or w/v

Example 1: A mixture contains 50 g sulfur, 30 g of potassium and 60 g of charcoal. Find the concentration of potassium nitrate in this mixture.

Solution: potassium = 30 g potassium = 30 g total mixture = 140 g (50 g + 30 g + 60 g) concentration = 30 g ÷ 140 g = g / g (ie grams of potassium per gram of mixture)

Example 2: 50 mL of 40% strength H 2 SO 4 (sulfuric acid) is added to 950 mL of water. Determine the concentration of the H 2 SO 4 in this solution.

Solution: Amount of H 2 SO 4 in the original mixture: Amount of H 2 SO 4 in the original mixture: 40% of 50 mL = 0.4 x 50 = 20mL of H 2 SO 4 Total amount of mixture: 50 mL mL = 1000 mL Concentration: 20 mL ÷ 1000 mL = 0.02 mL / mL

Example 3: A 250 mL can of RachaelsRidyaQuick Rat Solution contains 0.2 g of Killadeadroxide. Express the concentration of Killadeadroxide in: A) g / L B) as a % w / v (kilogram /Litre)

Example 3: A 250 mL can of RachaelsRidyaQuick Rat Solution contains 0.2 g of Killadeadroxide. Express the concentration of Killadeadroxide in: A) g / L 0.2 grams ÷ 250 mL= g / mL = 0.8 g / Litre (1000 mL = 1 L) = 0.8 g / Litre (1000 mL = 1 L)

Example 3: A 250 mL can of RachaelsRidyaQuick Rat Solution contains 0.2 g of Killadeadroxide. Express the concentration of Killadeadroxide in: A) g / L 0.2 grams ÷ 250 mL= g / mL = 0.8 g / Litre (1000 mL = 1 L) = 0.8 g / Litre (1000 mL = 1 L) B) as a % w / v (kilogram per L) = 0.8 g / L = 0.8 g / L = kg / L = kg / L = x 100% / L = x 100% / L = 0.08% w/v = 0.08% w/v

Exercise 2I pg 50 #4abcd, 8abc, 10ab, 14abc, 16ab, 18abc, 22abcd, 25abcd

Mars Bar Question Your vet has recommended a vitamin supplement for your guinea pigs at the rate of 10 g per litre in their drinking water. The solution you are sold states the concentration is 300g / 300 mL. How many mL of the solution should you add to the guinea pigs’ 500 mL water bottle? Your vet has recommended a vitamin supplement for your guinea pigs at the rate of 10 g per litre in their drinking water. The solution you are sold states the concentration is 300g / 300 mL. How many mL of the solution should you add to the guinea pigs’ 500 mL water bottle?