SolWorks

Solutions, molarity, dilution, electrolytes, solution stoichiometry, solubility and colligative properties.
Every topic has a live beaker you can drag. Each tab has Hint, Reset and Skip, 3 levels and a crown to win.

Track 0 · Introductory Chemistry · part of ChemTracks

Start here: how much is dissolved?

A solution is solute spread through a solvent. Almost every question is: how many moles are in how much solution? Every tab has a live beaker: drag a slider, see the particles respond, then practise.

Idea	Formula	Watch out for
Molarity	M = mol ÷ L	litres of solution, not solvent
Dilution	M₁V₁ = M₂V₂	moles do not change
Ions	[ion] = M × ions per unit	count ions, not formulas
Molality	m = mol ÷ kg solvent	kg of solvent
Freezing / boiling	ΔT = i K m	i = particles per unit

Build it, test it, own it

Read the idea, move the model, then practise. Every tab has Hint, Reset and Skip, 3 levels, and a crown to win. You never need to memorize: the model shows you why.

Sense check

Before you press Check, ask: does this make chemical sense? Diluting must lower M. A precipitate cannot weigh more than the reactants allow.

Step 1. What is a solution?

A solution is a uniform mixture: the solute (smaller amount) dissolved in the solvent (usually water). Like dissolves like: polar and ionic solutes dissolve in polar solvents, nonpolar solutes in nonpolar solvents. Mass percent = solute mass ÷ solution mass × 100.

Worked example. 25 g NaCl in 175 g water: mass % = 25 ÷ 200 × 100 = 12.5 %.

Step 2. Molarity: how concentrated?

M = moles of solute ÷ litres of solution. Grams → moles (molar mass), mL → L. Drag the sliders in the live beaker: more moles darken the solution, more volume lightens it.

Worked example. 11.7 g NaCl (58.44 g/mol) in 250 mL: n = 0.200 mol, M = 0.200 ÷ 0.250 = 0.800 M.

Step 3. Dilution: adding water

Water adds volume but no solute, so the moles stay the same: M₁V₁ = M₂V₂. Diluting always lowers M.

Worked example. Dilute 50.0 mL of 6.00 M to 300 mL: M₂ = 6.00 × 50.0 ÷ 300 = 1.00 M.

Step 4. Electrolytes: count the ions

Ionic compounds split into ions in water: CaCl₂ → Ca²⁺ + 2 Cl⁻. Strong electrolytes split fully, weak ones partly, non-electrolytes (sugar) not at all. Ion concentration = formula concentration × ions per formula unit.

Worked example. 0.10 M CaCl₂: [Ca²⁺] = 0.10 M, [Cl⁻] = 0.20 M, total ions = 0.30 M.

Step 5. Reactions in solution

Turn each solution into moles (M × V in L), use the balanced equation’s mole ratio, then convert back to volume, molarity or grams of precipitate. For limiting reagents, divide moles by the coefficient: the smaller result runs out first.

Worked example. 25.0 mL of 0.100 M HCl + NaOH (1:1): n = 0.00250 mol, so 25.0 mL of 0.100 M NaOH neutralizes it.

The two nevers of chemistry

Step 6. Solubility and saturation

Solubility is the most solute that dissolves at a given temperature. On the curve = saturated; below = unsaturated; extra solute stays as crystals. Cooling a saturated solution pushes out crystals. Gases behave the opposite way: they are less soluble when hot.

Worked example. KNO₃: 169 g/100 g water at 80 °C, 32 g at 20 °C. Cooling 100 g water: 137 g of crystals form.

Step 7. Colligative properties

Some properties depend only on how many particles are dissolved: ΔT_f = i K_f m, ΔT_b = i K_b m, and Π = iMRT. The van’t Hoff factor i counts particles per formula unit (sugar 1, NaCl 2, CaCl₂ 3). Road salt lowers the freezing point of ice.

Worked example. 1.00 m NaCl: ΔT_f = 2 × 1.86 × 1.00 = 3.72 °C, so it freezes at −3.72 °C.

Practice solutions and molarity

SolWorks is Track 0 of ChemTracks. Every topic has a live beaker, a short lesson, three levels of randomly generated problems with hints and worked solutions, and a crown for mastering it. Earn all eight crowns for a certificate.

Topics covered

Solute, solvent, like dissolves like, mass percent and ppm
Molarity and preparing solutions
Dilution with M1V1 = M2V2 and mixing solutions
Strong, weak and non-electrolytes and ion concentrations
Solution stoichiometry, neutralization, titration and limiting reagents
Solubility curves, saturation, crystallization and Henry's law
Molality, freezing point depression, boiling point elevation and osmotic pressure

Frequently asked questions

What does SolWorks cover?

Solutions and like-dissolves-like, mass percent and ppm, molarity, dilution, electrolytes and ion concentrations, solution stoichiometry and titration, solubility curves and saturation, and colligative properties.

How do I calculate molarity?

Molarity is moles of solute divided by litres of solution. Convert grams to moles with the molar mass and millilitres to litres first.

Which track is SolWorks in?

Track 0 (Introductory Chemistry) of ChemTracks. Every topic has a live beaker model you can drag.

Do I get a certificate?

Yes. Earn every crown in SolWorks and you can claim a free certificate of completion as a PDF. Finish all six Track 0 Works to also earn the Track 0 badge and certificate, which anyone can verify.

Do I need an account to use SolWorks?

No. It runs in your browser and saves your progress on your own device.