CHEM 1405 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.

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.

Solution Interactions

Type of Interaction	Solute-Solute Interaction	Solvent-Solvent Interaction	Solute-Solvent Interaction
Description:	· The interactions (attractions) between solute particles. · The strength and nature of these attractions is based on the IMFs (intermolecular forces) of the solute. · These attractions are overcome by solute-solvent interactions during solution formation.	· The interactions (attractions) between solvent particles. · The strength and nature of these attractions is based on the IMFs of the solvent. · These attractions are overcome by solute-solvent interactions during solution formation.	· The interactions (attractions) between solute particles and solvent particles. · The strength and nature of these attractions is based on the molecular structure of the solute and solvent and their respective IMFs.) · These attractions are what cause solution formation to occur.
Example:	In ionic compound KCl, K⁺ ions are attracted to Cl^- ions.	In water, the partially negative oxygen of one H₂O is attracted to the partially positive hydrogen of other H₂O molecules.	When NaCl dissolves in water, the partially negative O’s in H₂O surround Na⁺ ions and the partially positive H’s in H₂O surround Cl^- ions.

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

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

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.