Solutions
Honors Chemistry
Notes
Molarity
2-11
Name
Hour
Calculating Solution Concentrations
Calculate the molarity of the following solutions:
1. 1.0 liter which contains 2 moles of solute.
2. 1.5 liters which contain 1.82 moles of sodium hydroxide.
3. 4.00 liters which contain 8.64 moles of hydrochloric acid.
4. 0.500 liter which contain 0.25 mole of potassium hydroxide.
5. 0.01 liter which contain 0.0010 moles of sodium chloride.
How many moles of NaOH are contained in:
6. 1.0 liter of a 1.0 molar solution.
7. 0.50 liter of a 1.0 molar solution.
8. 125 mL of a 0.50 molar solution.
9. 130 mL of a 3.50 molar solution.
10. 0.05 liter of a 0.005 molar solution.
How many liters of solution can be made from each of the following?
11. a 2.00 M solution using 80.00 g of sodium hydroxide.
12. a 0.500 M solution using 80.00 g tin (IV) sulfate.
13. a 0.600 M solution using 126.0 g of HNO3
14. a 0.10 M solution using 117.0 g of potassium dichromate.
15. a 0.20 M solution using 200.0 g of sodium carbonate.
Calculate the mass of solute needed to make the following solutions:
16. 1.0 liter of a 1.0 M magnesium hydroxide solution.
17. 10.0 liters of a 8.0 M iron (III) chloride solution.
18. 0.125 liter of a 2.40 M ammonium nitrate solution.
19. 750.0 mL of a 0.500 M sodium carbonate solution.
20. 125 mL of a 8.00 M hydrogen acetate solution.
Determine the answers to the following problems.
21. What is the molarity of a solution made by dissolving 23.0 grams NaCl in
enough water to make 40.0 mL of solution?
22. What mass of KNO3 is needed to make 2.0 L of a 0.20 molar solution?
23. How many grams of lead (II) nitrate are there in 500.0 mL of a 0.25 M solution?
24. What is the molarity of a solution made by dissolving 0.66 moles of NaI in
enough water to make 5.0 liters of solution?
25. How many moles are there in 50.0 mL of a 0.002 M solution of NaCl?
Dilutions
Dilutions
Solutions of known molarity are often available in the laboratory. You can use these to
make new solutions of lower concentrations by just adding more solvent. As you observed
in the inquiry molarity lab activity, the number of moles of solute does not change when a
solution is diluted.
MOLARITY (M) = moles of solute divided by liters of solution (solute + solvent)
If we rearrange the equation…then…
moles solute = Molarity x Liters of solution
In a dilution, the moles of solute before dilution = moles solute after dilution
Substitute from the previous equation…
Molarity x Volume before dilution = Molarity x Volume after dilution
M1V1 = M2V2
M1 and V1 represent the initial solution’s molarity and volume (before dilution), M2
and V2 represent the solution’s final molarity and volume after dilution. Volume can
be in either milliliters or liters as long as the units are the same for both V1 and V2.
You also need to be able to explain how to prepare a diluted solution in a
sentence or two if asked. See example 1 below.
Example 1:
A student needs to prepare 100.0 ml of 0.50M NaOH. He has a stock of 3.0M
NaOH. How does he prepare the desired solution?
First determine the volume of 3.0M NaOH needed:
(3.0M)(V1)? =
(0.50M)(0.100L)
V1 = 0.017 L or 17 mL
“Measure 17 ml of 3.0M NaOH, transfer to a volumetric flask and add water until
the final volume is 100.0 ml.”
Example 2
A student adds water to 25 ml of 4.0 M NaOH until the final volume is 40.0 ml.
What is the molarity of the new solution?
4.0M x 0.025L = ? x 0.040L
? = 2.5 M
Concept Practice:
A. Explain why, after a dilution is completed, the resulting solution is always of lower
concentration than the original.
B. Your experiment requires 5 ml of 1.0M KOH. You have 1 L of 0.5M KOH on the shelf. Can
you prepare the required solution? Explain your answer.
Problems:
1. How do you prepare 250.0 ml of 0.20 M NaCl from a stock of 1.0M NaCl?
2. How do you prepare 400.0 ml of 1.0M Zn(NO3)2 from a stock of 2.5M Zn(NO3)2 ?
3. What is the resulting concentration when 400.0 ml of 12 M H2SO4 is diluted to a
new volume of 500.0 ml?
4. What is the resulting concentration when 20.0 ml of 6.0M HCl is added to 100.0
ml of water? (Tricky!!!)
5. What volume of 2.0 M LiCl is needed to make 500.0 ml of 0.35M LiCl?
6. What is the molarity of a solution made by adding 50.0 ml water to 150.0 ml of 0.10M KOH?
7. What volume of 12.0 M HCl is needed to prepare 450. ml of 2.0 M HCl? How much water is needed ?
8. Determine the concentration of a solution made by diluting 75ml of 5.0M NaOH with 200.0 ml of
water.
9. Determine the concentration of stock solution used when 40.0 ml of it are
needed to make 800.0 ml of 0.20 M HC2H3O2 .
10. Determine the volume of 1.0M KBr needed to prepare 500.0 ml of 0.20 M KBr.
Molarity, Stoich, % Mass
Solution Math
1. What is the molarity of a solution made by dissolving 23.0 grams NaCl in enough
water to make 40.0 mL of solution?
2. What mass of KNO3 is needed to make 2.0 L of a 0.20 molar solution?
3. Determine the percent by mass of solute in a solution containing 134g of Pb(NO3)2 in 266g of
water?
4. How many grams of lead(II) nitrate are there in 500.0 mL of a 0.25 M solution?
5. What is the molarity of a solution made by dissolving 0.66 moles of NaI in
enough water to make 5.0 liters of solution?
6. How many grams of water are needed to make a 25% by mass hydrochloric acid solution using 200g
of HCl?
7. How many moles are there in 50.0 mL of a 0.002 M solution of NaCl?
8. Accurately explain how to prepare 250.0 mL of a 0.20 M silver nitrate solution.
Use the equation below to answer the following questions.
K4FeC6N6 (aq) + 2 Zn(NO3)2 (aq) --> 4 KNO3 (aq) + Zn2FeC6N6 (s)
9. What volume of 2.5 M zinc nitrate is needed to produce 1.8g of zinc
ferrocynide?
10. If 20.5 mL of 0.12 M potassium ferrocynide and 15.8 mL of 0.20 M zinc nitrate
react, how many grams of zinc ferrocynide is formed?
11. Determine the volume of 0.3 M zinc nitrate needed to completely react with
34.9 mL of 0.50 M potassium ferrocynide?
Use the equation below to answer the following questions.
K2CrO4 (aq) + 2 AgNO3 (aq) ---> 2 KNO3 (aq) + Ag2CrO4 (s)
12. Determine the number of moles of potassium nitrate produced when 67mL of
1.2 M potassium chromate react with 56 mL of 0.98 M silver nitrate.
13. Determine the volume of .070 M silver nitrate needed to precipitate out all the
CrO4-2 ions from 22 mL of 0.30 M potassium chromate.
14. Determine the mass of silver chromate produced from 84 mL of 1.3 M silver nitrate.
15. What volume of 0.25 M potassium chromate is needed to completely react with
15.6 g of silver nitrate?
Use the equation below to answer the following questions.
2 Al(NO3)3 (aq) + 3 (NH4)2S (aq) ---> Al2S3 (s) + 6 NH4NO3
(aq)
16. Determine the volume of 0.40 M ammonium sulfide needed to completely react
with 9.6g of aluminum nitrate.
17. Determine the mass of aluminum sulfide produced from 112 mL of
3.4 M (NH4)2S.
18. How many moles of NH4NO3 are produced from 12.3 mL of 0.10 M (NH4)2S
reacting with 15.2 mL of 0.15 M Al(NO3)3 ?
Review
c15 Honors
1-11
Solution Math Review
1. Accurately explain how to prepare 2.0 L of a 1.5 M copper (II) nitrate solution.
2. How much water is needed to make 3.0 L of 35% HCl solution if the density of
the resulting solution is 1.1g/ml?
3. How many grams of sodium hydroxide must be weighed out to make 2.0L of 3.0M NaOH solution?
4. What is the % by mass of a solution made by dissolving 35.8 grams of silver nitrate in 500. grams
of water?
5. What is the molarity of 2.56 moles of potassium iodide dissolved in 250. mL of solution?
Use the equation below to answer the following questions.
Na2CO3 (aq) + 2 AgNO3 (aq) --> 2 NaNO3 (aq) + Ag2CO3 (s)
6. Determine the volume of 0.10 M silver nitrate needed to completely react with
125 mL of 0.15 M sodium carbonate?
7. Calculate the mass of Ag2CO3 formed when 45 mL of 1.2 M silver nitrate reacts completely?
8. What volume of 1.5 M silver nitrate is needed to produce 10.4g of Ag2CO3 ?
9. If 40.5 mL of 0.15M silver nitrate reacts with 30.0 mL of 0.12 M Na2CO3 , what
mass of Ag2CO3 is formed?
Use the equation below to answer questions 10-14.
2 Al(NO3)3 (aq) + 3 (NH4)2S (aq) ---> Al2S3
(s)
+ 6 NH4NO3
(aq)
10. Determine the volume of 0.80 M ammonium sulfide needed to completely react
with 150.0 mL of 0.50 M aluminum nitrate.
11. Determine the mass of Al2S3 produced when 450.0 mL of 3.5 M (NH4)2S reacts completely.
12. How many moles of Al2S3 are produced from 125 mL of 0.30 M Al(NO3)3
mixed with 100.0 mL of 0.50 M (NH4)2S ?
13. Determine the number of moles of NH4NO3 produced when 425mL of 3.0 M Al(NO3)3
reacts completely.
14. How many moles of aluminum nitrate are needed to completely react with 0.5 L of 0.25 M ammonium
sulfide?
15. If you prepared a saturated solution of sodium nitrate at room temperature and then heated it to
about 75°C, would the solution still be saturated? Explain.
16. Explain why carbonated beverages become flat when left opened.
Answers
Calculating Solution
Concentrations
Solution Math
1. 2M
2. 1.2M
1. 9.83M
2. 40. g
3. 2.16M
4. 0.50M
3. 33.5%
4. 41 g
5. 0.1M
6. 1.0 mol
5. 0.13M
6. 600 g
7. 0.50 mol
7. 1x10-4mol
8. 0.063 mol
8. 8.5g show math w explanation
9. 0.46 mol
10. 0.0003 mol
9. 0.0042 L
10. 0.54 g
11. 1.00 L
12. 0.515 L
11. 0.1 L
12. 0.055 mol
13. 3.33 L
14. 4.0 L
13. 0.19 L
14. 18 g
15. 9.4 L
16. 58 g
15. 0.18 L
16. 0.17 L
17. 12,984 g w SF 13,000 g
18. 24.0 g
17. 19 g
18. 0.0025 mol
19. 39.8 g
20. 60.0 g
21. 9.83 M
22. 40. g
23. 41 g
24. 0.13M
25. 0.0001 mol
Solution Math Review
1. need calculation and explanation
2. 2145 g with SF 2100 g
3. 240 g
4. 6.68%
5. 10.2M
6. 0.38 L
Dilutions
1. 50. mL
7. 7.4 g
8. 0.050 L
2. 160 mL
3. 9.6M
9. 0.84 g
10. 0.14 L
4. 1.0M
5. 88 mL
11. 79 g
12. 0.017 mol
6. 0.075M
7. 75 mL of HCl and 375 mL of
water
13. 3.8 mol
8. 1.4M
9. 4.0M
10. 100 mL
14. 0.08 mol
15. Think back to solubility graphs and
vocab
16. Think back to solubility graphs and
vocab
Notes