PROBLEM \(\PageIndex{1}\)
Explain what changes and what stays the same when 1.00 L of a solution of NaCl is diluted to 1.80 L.
- Answer
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The number of moles always stays the same in a dilution.
The concentration and the volumes change in a dilution.
PROBLEM \(\PageIndex{2}\)
What does it mean when we say that a 200-mL sample and a 400-mL sample of a solution of salt have the same molarity? In what ways are the two samples identical? In what ways are these two samples different?
- Answer
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The two samples contain the same proportion of moles of salt to liters of solution, but have different numbers of actual moles.
PROBLEM \(\PageIndex{3}\)
Determine the molarity for each of the following solutions:
- 0.444 mol of CoCl2 in 0.654 L of solution
- 98.0 g of phosphoric acid, H3PO4, in 1.00 L of solution
- 0.2074 g of calcium hydroxide, Ca(OH)2, in 40.00 mL of solution
- 10.5 kg of Na2SO4·10H2O in 18.60 L of solution
- 7.0 × 10−3 mol of I2 in 100.0 mL of solution
- 1.8 × 104 mg of HCl in 0.075 L of solution
- Answer a
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0.679 M
- Answer b
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1.00 M
- Answer c
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0.06998 M
- Answer d
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1.75 M
- Answer e
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0.070 M
- Answer f
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6.6 M
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PROBLEM \(\PageIndex{4}\)
Determine the molarity of each of the following solutions:
- 1.457 mol KCl in 1.500 L of solution
- 0.515 g of H2SO4 in 1.00 L of solution
- 20.54 g of Al(NO3)3 in 1575 mL of solution
- 2.76 kg of CuSO4·5H2O in 1.45 L of solution
- 0.005653 mol of Br2 in 10.00 mL of solution
- 0.000889 g of glycine, C2H5NO2, in 1.05 mL of solution
- Answer a
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0.9713 M
- Answer b
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5.25 × 10-3 M
- Answer c
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6.122 × 10-2 M
- Answer d
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7.62 M
- Answer e
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0.5653 M
- Answer f
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1.13 × 10-2 M
PROBLEM \(\PageIndex{5}\)
Calculate the number of moles and the mass of the solute in each of the following solutions:
(a) 2.00 L of 18.5 M H2SO4, concentrated sulfuric acid
(b) 100.0 mL of 3.8 × 10−5 M NaCN, the minimum lethal concentration of sodium cyanide in blood serum
(c) 5.50 L of 13.3 M H2CO, the formaldehyde used to “fix” tissue samples
(d) 325 mL of 1.8 × 10−6 M FeSO4, the minimum concentration of iron sulfate detectable by taste in drinking water
- Answer a
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37.0 mol H2SO4
3.63 × 103 g H2SO4
- Answer b
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3.8 × 10−6 mol NaCN
1.9 × 10−4 g NaCN
- Answer c
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73.2 mol H2CO
2.20 kg H2CO
- Answer d
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5.9 × 10−7 mol FeSO4
8.9 × 10−5 g FeSO4
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PROBLEM \(\PageIndex{6}\)
Calculate the molarity of each of the following solutions:
(a) 0.195 g of cholesterol, C27H46O, in 0.100 L of serum, the average concentration of cholesterol in human serum
(b) 4.25 g of NH3 in 0.500 L of solution, the concentration of NH3 in household ammonia
(c) 1.49 kg of isopropyl alcohol, C3H7OH, in 2.50 L of solution, the concentration of isopropyl alcohol in rubbing alcohol
(d) 0.029 g of I2 in 0.100 L of solution, the solubility of I2 in water at 20 °C
- Answer a
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5.04 × 10−3 M
- Answer b
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0.499 M
- Answer c
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9.92 M
- Answer d
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1.1 × 10−3 M
PROBLEM \(\PageIndex{7}\)
There is about 1.0 g of calcium, as Ca2+, in 1.0 L of milk. What is the molarity of Ca2+ in milk?
- Answer
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0.025 M
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PROBLEM \(\PageIndex{8}\)
What volume of a 1.00-M Fe(NO3)3 solution can be diluted to prepare 1.00 L of a solution with a concentration of 0.250 M?
- Answer
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0.250 L
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PROBLEM \(\PageIndex{9}\)
If 0.1718 L of a 0.3556-M C3H7OH solution is diluted to a concentration of 0.1222 M, what is the volume of the resulting solution?
- Answer
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0.5000 L
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PROBLEM \(\PageIndex{10}\)
What volume of a 0.33-M C12H22O11 solution can be diluted to prepare 25 mL of a solution with a concentration of 0.025 M?
- Answer
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1.9 mL
PROBLEM \(\PageIndex{11}\)
What is the concentration of the NaCl solution that results when 0.150 L of a 0.556-M solution is allowed to evaporate until the volume is reduced to 0.105 L?
- Answer
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0.794 M
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PROBLEM \(\PageIndex{12}\)
What is the molarity of the diluted solution when each of the following solutions is diluted to the given final volume?
- 1.00 L of a 0.250-M solution of Fe(NO3)3 is diluted to a final volume of 2.00 L
- 0.5000 L of a 0.1222-M solution of C3H7OH is diluted to a final volume of 1.250 L
- 2.35 L of a 0.350-M solution of H3PO4 is diluted to a final volume of 4.00 L
- 22.50 mL of a 0.025-M solution of C12H22O11 is diluted to 100.0 mL
- Answer a
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0.125 M
- Answer b
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0.04888 M
- Answer c
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0.206 M
- Answer d
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0.0056 M
PROBLEM \(\PageIndex{13}\)
What is the final concentration of the solution produced when 225.5 mL of a 0.09988-M solution of Na2CO3 is allowed to evaporate until the solution volume is reduced to 45.00 mL?
- Answer
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0.5005 M
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PROBLEM \(\PageIndex{14}\)
A 2.00-L bottle of a solution of concentrated HCl was purchased for the general chemistry laboratory. The solution contained 868.8 g of HCl. What is the molarity of the solution?
- Answer
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11.9 M
PROBLEM \(\PageIndex{15}\)
An experiment in a general chemistry laboratory calls for a 2.00-M solution of HCl. How many mL of 11.9 M HCl would be required to make 250 mL of 2.00 M HCl?
- Answer
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42.0 mL
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PROBLEM \(\PageIndex{16}\)
What volume of a 0.20-M K2SO4 solution contains 57 g of K2SO4?
- Answer
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1.6 L
PROBLEM \(\PageIndex{17}\)
The US Environmental Protection Agency (EPA) places limits on the quantities of toxic substances that may be discharged into the sewer system. Limits have been established for a variety of substances, including hexavalent chromium, which is limited to 0.50 mg/L. If an industry is discharging hexavalent chromium as potassium dichromate (K2Cr2O7), what is the maximum permissible molarity of that substance?
- Answer
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4.8 × 10−6 M
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