Chemistry: molar masses, balanced reactions, solutions and pH

Proofline has three chemistry cells that run in your browser: Chemistry: molar mass, Chemistry: reaction balancer and Chemistry: solutions, gases and pH. They use the standard atomic weights of IUPAC and the same engine as the Molar Mass & Composition Calculator, the Chemical Equation Balancer & Stoichiometry tool and the Solution, Gas Law & pH Calculator, so a cell and its tool page give identical numbers.

1. Open the Chemistry bench

Choose Notebook → Templates… and open Chemistry bench, then press Run all. The notebook holds ten chemistry cells. After a moment the status bar reads Done: 10 cells ran.

2. Molar mass and composition

Open the cell Copper(II) sulfate pentahydrate. The field Formulas (one per line) contains CuSO4·5H2O. The summary reads The molar mass of CuSO₄·5H₂O is 249.68 ± 0.02 g/mol. Open All result details for the composition table: copper is 25.451 % of the mass.

You can write nested brackets (K4[Fe(CN)6]), hydrates with ·, * or a dot, charges at the end (SO4^2-, Fe+3) and isotopes (^13C). Put several formulas on separate lines to compare them in one table.

The next cell, Glucose from its elemental analysis, uses the Calculation option Empirical formula from mass percentages. From C 40.0, H 6.71, O 53.29 and a molar mass of 180.16 it finds the empirical formula CH2O and the molecular formula C6H12O6.

3. Balance a reaction

Open Permanganate titration of iron(II). The Reaction field holds MnO4- + Fe+2 + H+ -> Mn+2 + Fe+3 + H2O, and the result is MnO₄⁻ + 5 Fe²⁺ + 8 H⁺ → Mn²⁺ + 5 Fe³⁺ + 4 H₂O. The table Atom and charge balance with the balanced coefficients shows that every element and the charge (17 on each side) are conserved.

Separate species with + (spaces around the plus), and use -> or = as the arrow. If the species allow several independent reactions, the cell says so and lists them, as with copper and nitric acid.

4. Limiting reagent and yield

Open Blast furnace: limiting reagent and yield. Under Starting amounts of reactants (optional) it has Fe2O3 = 100 g, CO = 50 g, and under Actual yield (optional) Fe = 60 g. The key figures show Limiting reagent CO, the theoretical yield of Fe (66.4584 g) and a Percentage yield of Fe of 90.28 %. The Stoichiometry table lists what reacts, what forms and what is left over.

On a balanced reaction without amounts, Continue with → Add starting amounts (10 g of each reactant) creates variant B with amounts you can edit.

5. Solutions, dilutions and gases

The cell Weigh out 250 mL of 0.1 M sodium chloride uses Molarity: solute, volume and concentration. Solute (mass or amount) is empty, so the cell calculates it: Dissolve 1.461 g (0.025 mol) of solute. Leave exactly one of the three fields empty.

Dilute 12 M hydrochloric acid to 1 M uses Dilution C1·V1 = C2·V2 with V1 empty: take 41.6667 mL of the stock and dilute to 500 mL. Molar volume of a gas at 0 °C and 1 atm uses Ideal gas law and partial pressures and finds 22.414 L. Type units with the numbers: 250 mL, 0.1 M, 25 °C, 1 atm.

From the copper sulfate cell, Continue with → Make a 0.1 M solution of CuSO₄·5H₂O (250 mL) adds a molarity cell; run it to get 6.24193 g.

6. pH and buffers

pH of 0.1 M acetic acid uses pH of acids, bases and buffers with Weak acid (Ka) and Ka 1.8e-5: the pH is 2.88. The table pH by method compares the exact charge balance with the quadratic and the √(K·c) shortcut.

The next cell is variant B: Buffer: weak acid + its conjugate base with equal amounts of acetic acid and acetate gives pH 4.74. The comparison shows how much the buffer raises the pH. On any weak-acid cell, Continue with → Make a buffer with the conjugate base creates such a variant for you.

Pin the figures you need — for example pH or Molar mass — and they appear in the Report view with their trend across runs.