CHEM 1406 Concept Review: Solutions

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Solutions and Electrolytes

Solution: A homogeneous mixture of 2 or more substances. A solution is composed of a solvent and solute(s).

Solute: The dissolved substance in a solution.

Solvent: The dissolving media of a solution. The solvent breaks down and assimilates solutes into itself.
The most common solutions have water as a solvent. Solutions with water as a solvent are called aqueous.

Electrolytes: Substances that form ions when dissolved in solution. Electrolytes can be weak or strong.

Strong Electrolytes: Substances that completely separate into their component ions when dissolved.

(All soluble ionic compounds and strong acids are strong electrolytes.)

Weak Electrolytes: Substances that exist in solution mostly as neutral molecules, with only a small

fraction separating into ions. (These are mostly weak acids and bases.)

Nonelectrolytes: Substances that do NOT form ions when dissolved in solution. These are usually molecular.

In Summary

Type of Solute	Dissociation	Particles in Solution	Conducts Electricity?	Examples
Strong Electrolyte	Complete	Ions only	Yes	Soluble ionic compounds such as NaCl, KBr, MgCl₂, NaOH, etc. Strong acids such as HCl, HBr, HNO₃, H₂SO₄, etc.
Weak Electrolyte	Partial	Mostly molecules and a few ions	Yes, but poorly	Weak acids and bases such as HF, H₂O, NH₃, HC₂H₃O₂ (acetic acid), etc.
Nonelectrolyte	None	Molecules only	No	Many carbon compounds such as CH₃OH (methanol), C₈H₁₈ (octane), C₂H₅OH (ethanol), C₁₂H₂₂O₁₁ (sucrose), CH₄N₂O (urea), etc.

Equivalent (Eq): The amount of an ion that will give 1 mol of either positive or negative charge

(Example: 1 mol of Na⁺is one equivalent, 1 mole of Ca²⁺ is 2 Eq, and 1mole of N^3- is 3 Eq.)

Solubility: The maximum amount of solute that is capable of dissolving in a given amount of solvent at a given temperature. Solubility changes with temperature, therefore a substance’s solubilities at different temperatures are usually represented on a solubility graph which has solubility on the y-axis and temperature on the x-axis.

Saturated Solution: A solution that has the maximum amount of solute capable of being dissolved at its current temperature. Any additional solute will not dissolve and simply fall to the bottom of the container.

Unsaturated Solution: A solution that contains LESS than the maximum amount of solute capable of being dissolved at its temperature. More solute could be added and dissolved in this solution.

Concentration of Solutions

$LaTeX: Concentration=\frac{amount\:of\:solute}{amount\:of\:solution}$ $Concentration=\frac{amount\:of\:solute}{amount\:of\:solution}$

This general equation summarizes all of the different concentration relationships. Four common concentrations used in chemistry are mass percent (m/m), volume percent (v/v), mass/volume percent (m/v), and Molarity.

Mass Percent (m/m): $LaTeX: Mass\:Percent\:\left(\frac{m}{m}\right)=\frac{mass\:of\:solute\:in\:grams}{mass\:of\:solution\:in\:grams\:\left(solution=solute+solvent\right)}\times100\%$ $Mass\:Percent\:\left(\frac{m}{m}\right)=\frac{mass\:of\:solute\:in\:grams}{mass\:of\:solution\:in\:grams\:\left(solution=solute+solvent\right)}\times100\%$

Volume Percent (v/v): $LaTeX: Volume\:Percent\:\left(\frac{v}{v}\right)=\frac{volume\:of\:solute}{volume\:of\:solution}\times100\%$ $Volume\:Percent\:\left(\frac{v}{v}\right)=\frac{volume\:of\:solute}{volume\:of\:solution}\times100\%$

Mass/Volume Percent (m/v): $LaTeX: Mass\:Volume\:Percent\:\left(\frac{m}{v}\right)=\frac{mass\:of\:solute\:in\:grams}{volume\:of\:solution\:in\:mL}\times100\%$ $Mass\:Volume\:Percent\:\left(\frac{m}{v}\right)=\frac{mass\:of\:solute\:in\:grams}{volume\:of\:solution\:in\:mL}\times100\%$

Molarity: $LaTeX: Molarity=\frac{moles\:of\:solute}{liters\:of\:solution}$ $Molarity=\frac{moles\:of\:solute}{liters\:of\:solution}$

When asked to solve for concentration, use the appropriate equation above. However, if given concentration, even though you could still use the matching equation from above, it is often much easier to use the given concentration as a conversion factor. See chart below.

Concentration as Conversion Factors

*Type of Concentration*	*Example*	*Meaning of Example*	*Example as a Conversion Factor*
Mass Percent (m/m)	10% (m/m) KCl solution	10 g KCl dissolved per 100 g of solution	$LaTeX: \left(\frac{10\:g\:KCl}{100\:g\:solution}\right)\:or\:\left(\frac{100\:g\:solution}{10\:g\:KCl}\right)$ $\left(\frac{10\:g\:KCl}{100\:g\:solution}\right)\:or\:\left(\frac{100\:g\:solution}{10\:g\:KCl}\right)$
Volume Percent (v/v)	12% (v/v) ethanol solution	12 mL ethanol dissolved per 100 mL of solution	$LaTeX: \left(\frac{12\:mL\:ethanol}{100\:mL\:solution}\right)\:or\:\left(\frac{100\:mL\:solution}{12\:mL\:ethanol}\right)$ $\left(\frac{12\:mL\:ethanol}{100\:mL\:solution}\right)\:or\:\left(\frac{100\:mL\:solution}{12\:mL\:ethanol}\right)$
Mass/Volume Percent (m/v)	15% (m/v) glucose solution	15 g of glucose dissolved per 100 mL of solution	$LaTeX: \left(\frac{15\:g\:glucose}{100\:mL\:solution}\right)\:or\:\left(\frac{100\:mL\:solution}{15\:g\:glucose}\right)$ $\left(\frac{15\:g\:glucose}{100\:mL\:solution}\right)\:or\:\left(\frac{100\:mL\:solution}{15\:g\:glucose}\right)$
Molarity	6.0 M HCl solution	6.0 mol of HCl dissolved per 1 L of solution	$LaTeX: \left(\frac{6.0\:mol\:HCl}{1\:L\:of\:solution}\right)=\left(\frac{1\:L\:of\:solution}{6.0\:mol\:HCl}\right)$ $\left(\frac{6.0\:mol\:HCl}{1\:L\:of\:solution}\right)=\left(\frac{1\:L\:of\:solution}{6.0\:mol\:HCl}\right)$

The Dilution Equation:

where C₁ and V₁ are the concentration and volume of the concentrated solution and C₂ and V₂ are the concentration and volume of the diluted solution.

$LaTeX: C_1\times V_1=C_2\times V_2$ $C_1\times V_1=C_2\times V_2$

Comparison of of the Particles of Solutions, Colloids, and Suspensions

Solutions	Colloids	Suspensions
Small particles such as atoms, ions, or small molecules	Large molecules or groups of molecules or ions	Very large particles that may be visible to the human eye
Particles do not settle	Particles do not settle	Particles settle out rapidly
Pass through filter paper unchanged	Pass through filter paper unchanged	Separated out by filter paper
Pass through membrane unchanged	Separated out by a membrane	Separated out by a membrane
Particles do not scatter light	Particles scatter light	Particles scatters light
Affect colligative properties	Do not affect colligative properties	Do not effect colligative properties

Colligative Properties: Properties that are determined solely by the number of solute particles in solution and the identity of the solvent, but NOT the identity of the solute particles. Three common colligative properties are freezing point lowering, boiling point elevation, and osmotic pressure.

Isotonic Solutions: Solutions that exert the same osmotic pressure as fluids in the body. (They have the same concentration of particles dissolved in solution.)

Hypotonic Solutions: Solutions with a lower solute concentration than body fluids. (pushes water into cells)

Hypertonic Solutions: Solutions with a higher solute concentration than body fluids. (pulls water out of cells)

Crenation: The shrinking of cells caused by hypertonic solutions action of pulling water out of cells.