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Solutions and Molarity

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Solutions and Molarity 4-20-09 What is a Solution? A Solution is a homogeneous mixture composed of two or more substances. Example: Salt Water (Fig 13-2, pg 469) NaCl ... – PowerPoint PPT presentation

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Title: Solutions and Molarity


1
Solutions and Molarity
  • 4-20-09

2
What is a Solution?
  • A Solution is a homogeneous mixture composed of
    two or more substances.
  • Example Salt Water
  • (Fig 13-2, pg 469)
  • NaCl(s) ? Na(aq) Cl(aq)

H2O
3
Solutions Consist of Two Things
  • Solvent is the substance in which the solute
    dissolves to make the solution. (Example Water)
  • Solute is the substance dissolved in a solution.
    (Example Salt)
  • Solutions are often called Aqueous. (A solution
    in which the solvent is H2O.)

4
Expressing Concentrations
  • The quantity of solute in a specific quantity of
    solvent is a measurement of the Concentration of
    the solution.
  • Concentration is measured in units of Molarity.
  • Molarity is the ratio of solute amount (in moles)
    to solution volume (in liters).

5
Molarity
  • Molarity
  • M
  • What is the Molarity of a solution that has a
    volume of 1.5L and contains 3.5 mols of NaCl?

moles of solute liters of solution
mol L
3.5 mols 1.5 L
2.33 M
6
Sample Problem 1
  • What is the Molarity of a solution that has a
    volume of 2.5L and contains 4.3 mols of NaCl?
  • But what if the question involved mL instead of L?

4.3 mols 2.5 L
1.72 M
7
Example (mL to L)
  • What is the Molarity of a solution that has a
    volume of 400mL and contains 5.2 mols of NaCl?
  • Now you try one!

5.2 mols 400 mL
1000 mL 1 L
13 M
8
Sample Problem 2
  • What is the Molarity of a solution that has a
    volume of 250mL and contains 3.8 mols of NaCl?
  • But what if the question involved grams instead
    of mols?

3.8 mols 250 mL
1000 mL 1 L
15.2 M
9
Example (grams to mols)
  • What is the Molarity of a solution that has a
    volume of 1.6L and contains 60 grams of NaCl?
  • Now you try one!

60 g NaCl 1.6 L
1 mol NaCl 58.45 g NaCl
0.64 M
10
Sample Problem 3
  • What is the Molarity of a solution that has a
    volume of 2.3L and contains 95 grams of NaCl?
  • But what if you were just given grams and mL in
    the question?

95 g NaCl 2.3 L
1 mol NaCl 58.45 g NaCl
0.71 M
11
Example (mL to L grams to mols)
  • What is the Molarity of a solution that has a
    volume of 600 mL and contains 75 grams of NaCl?
  • Now you try one!

1000 mL 1 L
75 g NaCl 600 mL
1 mol NaCl 58.45 g NaCl
2.14 M
12
Sample Problem 4
  • What is the Molarity of a solution that has a
    volume of 900 mL and contains 100 grams of NaCl?
  • Now what if I wanted to
  • make my own Molarity solution?

1000 mL 1 L
100 g NaCl 900 mL
1 mol NaCl 58.45 g NaCl
1.90 M
13
Example (Solute from Molarity)
  • How many grams of NaCl should be added to make a
    100mL flask of a 3.5 M solution?
  • Now you try one!

mol NaCl
1 L 1000 mL
100mL
3.5 1 L
58.45 g NaCl 1 mol NaCl
20.46 g of NaCl
14
Sample Problem 5
  • How many grams of NaCl should be added to make a
    500mL flask of a 5.4 M solution?
  • Can I dilute a Molarity
  • soln to make a new one?

mol NaCl
1 L 1000 mL
500mL
5.4 1 L
58.45 g NaCl 1 mol NaCl
157.82 g of NaCl
15
Example of Dilutions
  • You obtain 50 mL of a 4 M solution of NaCl. How
    many mL are in the final volume of a 2 M solution
    of NaCl?

M1V1 M2V2
(2M)
(4M)
(50mL)

(?mL)
(200)

(2)
(?mL)
Divide by 2 on both sides
mL

100
16
Sample Problem 6
  • You obtain 75 mL of a 5 M solution of NaCl. How
    many mL are in the final volume of a 4 M solution
    of NaCl?

M1V1 M2V2
(4M)
(5M)
(75mL)

(?mL)
(375)

(4)
(?mL)
Divide by 4 on both sides
mL

93.75
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