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| ap_chem:solutions_molarity [2020/10/27 18:49] – epix | ap_chem:solutions_molarity [2020/11/10 01:46] (current) – [Dilutions] epix | ||
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| ====== Solutions and Molarity ====== | ====== Solutions and Molarity ====== | ||
| === Solvent === | === Solvent === | ||
| - | The majority | + | The substance |
| === Solute === | === Solute === | ||
| - | The minority | + | The substance |
| === Solution === | === Solution === | ||
| A homogeneous mixture of two or more substances | A homogeneous mixture of two or more substances | ||
| - | ===== Molarity | + | ===== Molarity ===== |
| + | Molarity is the most common method to represent the concentration of solute particles in solution. | ||
| $\text{Molarity} = \frac{\text{mol solute}}{\text{L solution}}$ | $\text{Molarity} = \frac{\text{mol solute}}{\text{L solution}}$ | ||
| + | |||
| + | ==== Example ==== | ||
| + | > A 3.75g sample of NaCl is dissolved in water. The total volume of the solution is 768mL. What is the molarity of the solution? | ||
| + | $3.75\text{g NaCl} \times \frac{1 \text{ mol NaCl}}{58.44 \text{ g NaCl}} = 0.0642 \text{ mol NaCl}$ | ||
| + | |||
| + | $\text{Molarity} = \frac{0.0642 \text{ mol}}{0.768 \text{ L}} = 8.36\times10^{-2} \text{ M NaCl}$ | ||
| + | |||
| + | ===== Electrolytes ===== | ||
| + | When ionic compounds dissolve in water, it dissociates. These are known as electrolytes. | ||
| + | |||
| + | Common electrolytes include: | ||
| + | * NaCl (salt) | ||
| + | * NaNO< | ||
| + | * CaCl< | ||
| + | |||
| + | ===== Dilutions ===== | ||
| + | Lowering the concentration of solution (by adding more solvent). To determine the concentration of a solution, you can use the Dilution Equation. | ||
| + | |||
| + | $M_1V_1 = M_2V_{total}$ | ||
| + | |||
| + | Note that $M*V = \text{moles}$. $M$ represents molarity and $V$ volume. | ||
| + | |||
| + | ==== Example ==== | ||
| + | What if a 1M 10mL solution was diluted with 10mL extra water? | ||
| + | * $1M \times 10\text{mL} = ?M \times 20\text{mL}$ | ||
| + | * $M = 0.5M$ The result is a halved molarity! | ||
