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Year 11 / Aqueous solutions and acidity

Concentration counts amount per volume.

The solute is dissolved in the solvent to form a solution. Concentration in mol L1L^{-1} is amount of solute divided by final solution volume. Dissolving a solid in 100 mL of solvent does not necessarily produce exactly 100 mL of solution.

Dilution adds solvent while preserving solute amount, so c₁V₁ = c₂V₂. Use the same volume units on both sides. For a fully dissociated ionic solute, ion concentrations follow the formula ratio; 0.10 M CaCl₂ gives 0.20 M chloride ions.

INTERACTIVE MODEL

Same solute, more solution

Concentration / mol L⁻¹: 0.5 · schematic
READ THE GRAPH

Explore the relationship

Dissolved amount remains constant during dilution. Volume is final solution volume.

Concentration / mol L⁻¹00.13130.26250.39380.5250.10.3250.550.7751Solution volume / L
Concentration / mol L⁻¹

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Explore the relationship
SeriesSolution volume / LConcentration / mol L⁻¹
Concentration / mol L⁻¹0.10.5
Concentration / mol L⁻¹0.1150.434783
Concentration / mol L⁻¹0.130.384615
Concentration / mol L⁻¹0.1450.344828
Concentration / mol L⁻¹0.160.3125
Concentration / mol L⁻¹0.1750.285714
Concentration / mol L⁻¹0.190.263158
Concentration / mol L⁻¹0.2050.243902
Concentration / mol L⁻¹0.220.227273
Concentration / mol L⁻¹0.2350.212766
Concentration / mol L⁻¹0.250.2
Concentration / mol L⁻¹0.2650.188679
Concentration / mol L⁻¹0.280.178571
Concentration / mol L⁻¹0.2950.169492
Concentration / mol L⁻¹0.310.16129
Concentration / mol L⁻¹0.3250.153846
Concentration / mol L⁻¹0.340.147059
Concentration / mol L⁻¹0.3550.140845
Concentration / mol L⁻¹0.370.135135
Concentration / mol L⁻¹0.3850.12987
Concentration / mol L⁻¹0.40.125
Concentration / mol L⁻¹0.4150.120482
Concentration / mol L⁻¹0.430.116279
Concentration / mol L⁻¹0.4450.11236
Concentration / mol L⁻¹0.460.108696
Concentration / mol L⁻¹0.4750.105263
Concentration / mol L⁻¹0.490.102041
Concentration / mol L⁻¹0.5050.0990099
Concentration / mol L⁻¹0.520.0961538
Concentration / mol L⁻¹0.5350.0934579
Concentration / mol L⁻¹0.550.0909091
Concentration / mol L⁻¹0.5650.0884956
Concentration / mol L⁻¹0.580.0862069
Concentration / mol L⁻¹0.5950.0840336
Concentration / mol L⁻¹0.610.0819672
Concentration / mol L⁻¹0.6250.08
Concentration / mol L⁻¹0.640.078125
Concentration / mol L⁻¹0.6550.0763359
Concentration / mol L⁻¹0.670.0746269
Concentration / mol L⁻¹0.6850.0729927
Concentration / mol L⁻¹0.70.0714286
Concentration / mol L⁻¹0.7150.0699301
Concentration / mol L⁻¹0.730.0684932
Concentration / mol L⁻¹0.7450.0671141
Concentration / mol L⁻¹0.760.0657895
Concentration / mol L⁻¹0.7750.0645161
Concentration / mol L⁻¹0.790.0632911
Concentration / mol L⁻¹0.8050.0621118
Concentration / mol L⁻¹0.820.0609756
Concentration / mol L⁻¹0.8350.0598802
Concentration / mol L⁻¹0.850.0588235
Concentration / mol L⁻¹0.8650.0578035
Concentration / mol L⁻¹0.880.0568182
Concentration / mol L⁻¹0.8950.0558659
Concentration / mol L⁻¹0.910.0549451
Concentration / mol L⁻¹0.9250.0540541
Concentration / mol L⁻¹0.940.0531915
Concentration / mol L⁻¹0.9550.052356
Concentration / mol L⁻¹0.970.0515464
Concentration / mol L⁻¹0.9850.0507614
Concentration / mol L⁻¹10.05
Concentration / mol L⁻¹: 0.5

Explore: Increase solution volume at fixed amount. Check that cV remains constant.

c=nVc1V1=c2V2c=\frac nV\qquad c_1V_1=c_2V_2
WORKED EXAMPLE

Dilute 20.0 mL of 0.50 M solution to a total of 100.0 mL.

  1. c₂ = 0.50 × 20.0100.0\frac{20.0}{100.0}.
  2. c₂ = 0.10 mol L1L^{-1}.
Assumed knowledge

Moles and millilitre-to-litre conversion.

Learning checkpoints & sourceYOUR LEARNING CHECKPOINT
  • Distinguish solute, solvent and solution.
  • Calculate molarity and dilution.
QCAA Chemistry · Unit 2 · Aqueous solutions and acidity
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