Concentration Review Worksheet Answers
1)
If I make a solution by adding 83 grams of sodium hydroxide to 750 mL of
water.
To solve problem 1, you need to have calculated for various parts
that there are 2.08 moles of NaOH (which has a molar mass of 40
g!mol), that there are 750 grams of water (which has a density of I
gImL), and that there are 41.67 moles of water (which has a molar
mass of 18 glmol).
2)
a)
What is the molality of sodium hydroxide in this solution?
2.77 m (2.08 mol I 0.75 kg water)
b)
What is the percent by mass of sodium hydroxide in this solution?
9.96% (found by finding 83 g I 833 g and multiplying by 100%)
c)
What is the mole fraction of sodium hydroxide in this solution?
0.0475 (found by finding 2.08 mol I 4375 mol)
If I make a solution by adding water to 35 mL of methanol (CH
OH) until
3
the final volume of the solution is 275 mL...
When solving this problem, you’ll need to calculate that there are
27.72 grams of methanol (from the density), which is equal to 0.866
mol.
a)
What is the molarity of methanol in this solution? (The density of
methanol is 0.792 gImL)
3.15 M (0.866 mol/0.275 L)
b)
What is the percent by volume of methanol in this solution?
12.7% ((35 mL/275 mL) X 100)
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Dilutions Worksheet SoIutions
1)
If ladd 25 mLofwaterto 125 mLofa 0.15 M NaOH solution, whatwill the
molarity of the diluted solution be?
V =M
1
M
V
2
(0.15 M)(125 mL) = x (150 mL)
x 0.125 M
2)
If I add water to 100 mL of a 0.15 M NaOH solution until the final volume is
150 mL, what will the molarity of the diluted solution be?
V =M
1
M
V
2
(0.15 M)(100 mL) = x (150 mL)
x = 0.100 M
3)
How much 0.05 M HCI solution can be made by diluting 250 mL of 10 M
HCI?
M =M
V
1
V
2
(10 M)(250 mL) = (0.05 M) x
x = 50,000 mL
4)
I have 345 mL of a 1.5 M NaCI solution. If I boil the water until the volume
of the solution is 250 mL, what will the molarity of the solution be?
V =M
1
M
V
2
(1.5 M)(345 mL) = x (250 mL)
x = 2.07 M
5)
How much water would I need to add to 500 mL of a 2.4 M KCI solution to
make a 1.0 M solution?
M =M
V
1
V
2
(2.4 M)(500 mL) (1.0 M) x
x = 1200 mL
1200 mL will be the final volume of the solution. However, since
there’s already 500 mL of soiution present, you only need to add 700
mL of water to get 1200 mL as your finat volume, The answer: 700
mL.
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—
All Rights Reserved