1 · Choose the solute
2 · Mass of solute, m
3 · Volume of solution, V
Particle view (zoomed in)
• water ● solute
• water ● solute
Molar concentration C–mol·L⁻¹
Mass concentration Cm–g·L⁻¹
Amount of solute n–mol
Live calculations
Try this 🔬
- Double the volume and keep the same mass. What happens to C?
- Add water: does n change? Does C change?
- Find two different (m, V) pairs that give the same color.
- Pick KMnO₄ with V = 50 mL and keep adding solid. What happens above about 3.2 g?
Missions
8 missions · new numbers every time you play · 2 tries per question.
📋 Your lab report
Copy this summary and send it to your teacher when you finish.
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Amount of substance
n = m / M
- n in mol
- m in g
- M (molar mass) in g·mol⁻¹
Molar concentration
C = n / V
- C in mol·L⁻¹
- V = volume of solution, in L
Mass concentration
Cm = m / V
- Cm in g·L⁻¹
- m = mass of dissolved solute, in g
Linking the two
Cm = C × M
Because m = n × M, dividing both sides by V gives Cm = C × M.
Dilution
C₀ × V₀ = C × V
Adding water does not change the amount of solute: n₀ = n.
F = C₀ / C = V / V₀
The dilution factor F has no unit and is greater than 1.
Unit tips
- 1 mL = 10⁻³ L, so 250 mL = 0.250 L
- Always convert V to liters inside a formula
- A result without a unit is incomplete
Glassware
- Volumetric flask: one gauge mark, prepares a precise volume of solution
- Volumetric pipette (with a pipette filler): takes a precise volume of liquid
- Graduated cylinder: approximate volume
- Beaker / Erlenmeyer: no precision
Atomic molar masses (g·mol⁻¹)
- H = 1 · C = 12 · O = 16
- Na = 23 · S = 32 · Cl = 35.5
- K = 39 · Cr = 52 · Mn = 55 · Cu = 63.5
Answering like a chemist
- Calculate / Determine: formula → substitution → result with unit
- Deduce: use your previous answer ("From part 1, …")
- Indicate: give the answer only, no justification
- Classify: put items in order and state the direction
For teachers
- Learning objectives: define and calculate mass concentration and molar concentration; relate Cm = C × M; describe the preparation of a solution from a solid; carry out a dilution (C₀V₀ = CV, dilution factor); estimate a concentration with a color scale.
- Lab mode is an open simulation for whole-class demonstration or exploration. Color follows a Beer–Lambert-type model; solubility limits (≈ 20 °C, rounded) make crystals appear when the solution is saturated.
- Missions are randomized each play, so students can't copy numbers. Each question allows 2 tries (full points, then half points); after that the model answer is shown so no student is ever stuck.
- Questions use the official CRDP action verbs (Calculate, Determine, Deduce, Indicate, Classify, Choose). Model answers show formula → substitution → result with unit; Indicate answers carry no justification.
- Numeric answers are accepted within ±2.5 % (rounding). Decimal comma and scientific notation (2.5e-3, 2.5×10^-3) are accepted. A correct number with a wrong unit is marked wrong, with a hint.
- Progress is saved only in each student's browser. Students copy their lab report from the Missions tab and send it to you.