Solutions
Dr. Ron Rusay
Fall 2001
Aqueous Reactions & Solutions
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1
Many reactions are done in a homogeneous liquid
or gas phase which generally improves reaction
rates.
The prime medium for many inorganic reactions is
water which serves as a solvent (the substance
present in the larger amount), but does not
react itself.
The substance(s) dissolved in the solvent is (are)
the solute(s). Together they comprise a solution.
The reactants are the solutes.
© Copyright 1995-2001 R.J. Rusay
Water : “The Universal” Solvent
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The oil (nonpolar)
and water (polar) mixture don’t mix and
H
are immiscible. If liquids form a homogeneous mixture,
they are miscible.
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04_40
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105
O
H
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Generally, likes dissolve likes, i.e. polar-polar and
nonpolar-nonpolar. If polar and nonpolar mix , eg.
oil and water:
Salt dissolving in a glass of water
Water dissolving an ionic solid
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Concentration and Temperature
Relative Solution
Concentrations:
Saturated
Unsaturated
Supersaturated
Besides amount, the rate also increases.
What are two other ways of increasing the
solubility of a solid, eg. sugar in coffee?
Gas Solubility
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Solubility @ P2 = Solubility @ P1 x [P2 / P1 ]
P is the partial pressure of the gas vapor.
Solubility units (Concentration) are usually: g / 100 ml
Preparation of Solutions
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Solution Concentration
1
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A solution’s concentration is the measure of the
amount of solute dissolved.
Concentration is expressed in several ways. One way
is mass percent.
Mass % = Mass solute / [Mass solute + Mass solvent ]
x100
What is the mass % of 65.0 g of glucose dissolved in
135 g of water?
Mass % = 65.0 g / [65.0 + 135]g x100
= 32.5 %
© Copyright 1995-2001 R.J. Rusay
Solution Concentration
1Concentration
is expressed more importantly as
molarity (M).
Molarity (M) = Moles solute / Liter
Solution
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An important relationship is M x Vsolution= mol
This relationship can be used directly in mass
calculations of chemical reactions.
What is the molarity of a solution of 1.00 g KCl in
75.0 mL of solution?
M = 1.00g KCl x 1mol KCl / 74.55 g KCl x 1/ 75mL x 1000mL / L
= 0.18 mol / L
© Copyright 1995-2001 R.J. Rusay
Solution Dilution
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Sorenson Video decompressor
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Solution Dilution
Calculations
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following formula can be used in dilution
calculations:
M1V1 = M2V2
A concentrated stock solution is much easier to
prepare and then dilute rather than preparing a
dilute solution directly. Concentrated sulfuric acid
is 18M. What volume would be needed to prepare
250mL of a 1.5M solution?
V1 = M2V2 / M1
V1 = 1.5 M x 250 mL / 18 M = 20.8 mL
© Copyright 1995-2001 R.J. Rusay
Solution Problems
1
1) What is the mass of copper(II)chloride in
25.0 mL of a 0.500M solution? massCuCl2 = ? 1.81g
2) 10.00 mL of concentrated acetic acid (17M) was
diluted to make exactly 500.00 mL of solution.
What is M2 = ? 0.34 M
3) 50.0 mL of a 0.100M MgBr2 solution reacted
completely with 13.9 mL of a silver nitrate
solution. MAgNO3= ? ; massAgBr = ?
0.719 M
© Copyright 1995-2001 R.J. Rusay
1.88 g