15.3 Calculate the Concentration of a Solution in Titration using Empirical Data

📌 15.3 concentration by titration

“The concentration of a solution can be determined by titrating it with a solution of known concentration till the end point. You need balanced equation, volumes, and one known concentration.”

TITRATION TRIANGLE: 1) write balanced eq → 2) mole ratio → 3) conc = moles / volume (dm³)

⚖️ CuSO₄ · 5×10⁻² mol/dm³

Problem: What mass of CuSO₄ is present in 50 cm³ of a 5×10⁻² mol/dm³ aqueous solution?

Molar mass CuSO₄ = 159.5 g/mol (approx)
Volume = 50 cm³ = 0.05 dm³
moles = (5×10⁻²) × 0.05 = 2.5×10⁻³ mol
mass = 2.5e-3 × 159.5 = 0.39875 g ≈ 0.4 g

move decimal: cm³ → dm³ = ÷1000. milli → moles → mass.

🧴 15.5 example (HCl mass → conc)

500 cm³ of hydrochloric acid contains 1.8 g HCl. concentration in g/dm³?

volume = 500/1000 = 0.5 dm³
conc (g/dm³) = mass/volume = 1.8/0.5 = 3.6 g/dm³

g/dm³ = (mass in g) / (volume in dm³) — easy!

⚗️ 15.8 titration NaOH + HCl

“15 cm³ NaOH (0.5 mol/dm³) neutralizes 23 cm³ HCl. Find conc of HCl.”

NaOH + HCl → NaCl + H₂O (1:1)
moles NaOH = 0.5 × 0.015 = 0.0075 mol
=> moles HCl = 0.0075 mol
[HCl] = 0.0075 / 0.023 = 0.326 mol/dm³

ratio 1:1 → MₐVₐ = M_bV_b (if both monoprotic)

📚 15.3 Quick check (oxalic acid + KOH)

“Calculate volume of 0.1 mol/dm³ oxalic acid (C₂H₂O₄) to neutralize 25 cm³ 0.1 mol/dm³ KOH.”

C₂H₂O₄ + 2KOH → K₂C₂O₄ + 2H₂O (1:2 ratio)
moles KOH = 0.1 × 0.025 = 0.0025 mol
moles oxalic acid needed = 0.0025/2 = 0.00125 mol
Volume = 0.00125 / 0.1 = 0.0125 dm³ = 12.5 cm³

acid : base = 1:2 → divide base moles by 2 before using M=n/V.

📋 10 MCQs · titration

🔑 answer key & result (after submit)

📅 35‑min lesson planner · titration stoichiometry

⏳ 0-5 min
🧪 hook: demo colour change

5-12 min
📐 mole bridge (M=n/V)

12-20 min
⚖️ worked examples (NaOH+HCl)

20-28 min
✏️ pair activity: solve CuSO₄ mass

28-35 min
📊 quiz + reflection

🎯 activities: “acid‑base race” — groups get different volumes, find unknown conc. • “memory chain” using hand signs for 1:1 / 1:2 ratios. • quick whiteboard drills: cm³ → dm³.

✅ all examples from textbook covered: 15.3 CuSO₄, 15.5 HCl g/dm³, 15.8 NaOH+HCl, oxalic+KOH quick check.

🧪 titration · stoichiometry

📋 10 MCQs · titration

📅 35‑min lesson planner · titration stoichiometry