Chapter 13 · Solutions
13.8Solution Stoichiometry
12 min · two checks
Predict
What is the map from milliliters of A to grams of product?
The idea
- Solve a precipitation or acid–base problem in solution.
- Keep volumes in liters when using molarity.
Solution stoichiometry inserts molarity at the front of the Chapter 8 map. Convert the given volume to liters, multiply by molarity to get moles, use the balanced equation, and convert the product moles to whatever was asked: grams, or liters of another solution. If two solutions are mixed and you need the limiting reactant, compute moles of each and compare using coefficients, exactly as with masses.
A titration is this pattern used to find an unknown concentration: you know the mole ratio, you measure both volumes, and you know one molarity. At the equivalence point the moles of acid and base match the ratio, not necessarily 1:1. Sulfuric acid with sodium hydroxide is 1:2. Write the equation before you assume one-to-one.
Keep these
- Volume × molarity = moles.
- Then use the ordinary mole ratio.
- Check the balanced ratio in a titration. It is not always 1:1.
Worked path
What mass of AgCl forms when 40.0 mL of 0.150 M AgNO₃ reacts with excess NaCl? AgNO₃ + NaCl → AgCl + NaNO₃. Molar mass AgCl = 143.3 g/mol.
Observe
Moles AgNO₃ = 0.0400 × 0.150 = 0.00600. Ratio to AgCl is 1:1.