Post on 03-Jan-2016
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Calculating concentrations
Different ways to express concentration:
• Number of grams of solute per liter of solution (g/L)
• Number of grams of solute per 100 ml of solution (%mass /volume = %m/V)
• Number of millilitres of solute per 100 ml of solution (% volume/volume = %V/V)
• Number of grams of solute per 100 grams of solution (% mass/ mass = %m/m)
c =amount solute
amount solution
grams of solute per liter of solution (g/L)
c =amount solute
amount solutionc =
mass of solutevolume of solution
c =mv
in gin L
conversions1.000 L =
0.100 L =
10 mL =
1 mL =
1000 mg =
100 mg =
0.010 g =
0.001 g =
1000 mL
100 mL
0.010 L
0.001 L
1.000 g
0.100 g
10 mg
1 mg
mg
19 g sugar
m = 19 gv = 200 ml
c = 19 g 0.2 L
c =mv
c = 95 g /L
m = 53.5 mg
v = 1 L
c =mv
c = 0.0535 g 1 L
c = 0.0535 g /L
known:
formula:
known:
formula:
= 0.2 L
= 0.0535 g
example• How much sugar do you need if you want to
make 20 ml of a sugar solution with a concentration of 50 g/L?
c =mv
c = 50 g/L
v = 20 mL = 0.02 L
m = ?
50 g/L = x g 0.02 L
x = 1 g
known: formula:
m = 1 g
Different ways to express concentration:
• Number of grams of solute per liter of solution (g/L)
• Number of grams of solute per 100 ml of solution (%mass /volume = %m/v)
• Number of millilitres of solute per 100 ml of solution (% volume/volume = %v/v)
• Number of grams of solute per 100 grams of solution (% mass/ mass = %m/m)
c =amount solute
amount solution
grams of solute per 100 ml of solution: % m/v
• 3.25 % MF
• 1 % MF
3.25 g milk fat100 ml milk
100 ml milk 1 g milk fat
c =amount solute
amount solution
grams of solute per 100 ml of solution: % m/v
0.243 g Sodium fluoride
100 ml of tooth paste
example• Determine the concentration of a solution of
20 g solute in 250 mL final solution in % m/v.
m = 20 gv = 250 mL
c =mv
x 20 g 250 mL
x g = 20 g × 250 mL
100 mL
x = 8 gc = 8 %m/v
known: formula:
c = xg /100 mL = x %m/v
100 mL=
g
Different ways to express concentration:
• Number of grams of solute per liter of solution (g/L)
• Number of grams of solute per 100 ml of solution (%mass /volume = %m/v)
• Number of millilitres of solute per 100 ml of solution (% volume/volume = %v/v)
• Number of grams of solute per 100 grams of solution (% mass/ mass = %m/m)
c =amount solute
amount solution
100 ml of vinegar
5 ml acetic acid
milliliters of solute per 100 ml of solution, % v/v
100 ml of beer
7.9 ml ethanol
example• How much ethanol (in mL) is there in a 750 mL
bottle of wine with an alcohol concentration of 12 %v/v?
c =amount solute
amount solution
12 mL x mL
known:
c = 12 mL / 100 mL
v = 750 mL
amount of solute = x mL
c = 100 mL
= 750 mL
x = 90 mL
amount of solute in 750 mL = 90 mL
Different ways to express concentration:
• Number of grams of solute per liter of solution (g/L)
• Number of grams of solute per 100 ml of solution (%mass /volume = %m/v)
• Number of millilitres of solute per 100 ml of solution (% volume/volume = %v/v)
• Number of grams of solute per 100 grams of solution (% mass/ mass = %m/m)
c =amount solute
amount solution
grams of solute / 100 g of solution: % m/m
18 Ka = 750 / 1000
75 g gold 100 g alloy
= 75 % m/m
example• What is the % m/m carbon concentration of
steel made by adding 3g of Carbon to 147 g of iron?
c =amount solute
amount solutionknown:
c = x g / 100 g
amount of solution = 147 + 3 g
amount of solute = 3 g c = x g
100 g = 3 g
150 g
x = 2 g
c = 2 g / 100 g = 2 % m/m
Homework
• Work book page 8 / 9; # 1, 2, 3, 6, 7• Conversion work sheet
c =amount solute
amount solution
100ml