Other important AP CHEM things
TL DR: Just multiply the subscript by the molarity
Ion concentration is the measure of the amount of ions present in a solution. It is typically expressed in units of molarity (M), which is defined as the number of moles of solute per liter of solution.
Steps to Calculate Ion Concentration
- Determine the moles of solute present in the solution. This can be done by using the formula: $$ \text{Moles Of Solute} = \frac{\text{mass of solute (g)} }{\text{molar mass of solute (g/mol)}} $$ 2. Convert the moles of solute to moles of ions. This is done by multiplying the moles of solute by the number of ions produced by each molecule of solute. For example, if the solute is NaCl, then each molecule of NaCl produces one Na+ ion and one Cl- ion. Therefore, the moles of ions would be twice the moles of solute.
- Calculate the volume of the solution in liters.
- Divide the moles of ions by the volume of the solution to obtain the ion concentration.
Equations
The following equations can be used to calculate ion concentration:
- molarity (M) = moles of solute / liters of solution
- Moles of ions = moles of solute × number of ions produced per molecule of solute
- Liters of solution = volume of solution / 1000 mL
Example
Calculate the molarity of a solution that contains 5.85 g of NaCl in 250 mL of solution.
Step 1: Calculate the moles of NaCl present in the solution.
$$ \text{moles of NaCl} = \frac{5.85 \text{ g}}{58.44 \text{ g / mol}} = 0.100\text{ mol}
$$ Step 2: Convert the moles of NaCl to moles of ions.
$$ \text{moles of ions} = 0.100 \text{ mol} × 2 = 0.200 \text{ mol}
$$ Step 3: Calculate the volume of the solution in liters.
$$ \text{liters of solution} = \frac{250 \text{mL}}{1000 \text{ mL/L}} = 0.250 \text{L}
$$ Step 4: Divide the moles of ions by the volume of the solution to obtain the ion concentration.
$$ \text{molarity (M)} = \frac{0.200 \text{mol} }{ 0.250 \text{L}} = 0.800 \text{M}
$$
Therefore, the molarity of the solution is 0.800 M.