Stoichiometry, solutions, pH, and gas laws in one chemistry calculator: moles from mass, Avogadro’s number, molarity, dilutions, pH and pOH, percent yield and composition, limiting reactant, and PV = nRT — pick the formula from the dropdown.
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FORMULA USEDChemistry Calculator
One page for stoichiometry, solutions, and gases
Choose the formula from the dropdown and the form adapts: two fields for moles from mass, five for the limiting reactant, four for the ideal gas law — where you leave one blank and the tool solves for it. Every result shows the substituted calculation beneath the board, the same way the rest of the manual works.
The constants this page uses
Avogadro’s number NA = 6.022×10²³ particles per mole. The gas constant R = 0.08206 L·atm/(mol·K) — which means pressure in atmospheres, volume in liters, temperature in kelvin. The water constant Kw = 1.0×10⁻¹⁴ at 25 °C, the source of pH + pOH = 14. Celsius converts with K = °C + 273.15.
Where each formula applies
Stoichiometry runs on n = m/M: grams become moles, moles ride the balanced equation’s coefficients, moles become grams again. Solutions use molarity M = n/V, and C₁V₁ = C₂V₂ when only solvent is added. Acids and bases trade pH, pOH, and concentration through logarithms and Kw. Gases need kelvin always — doubling 25 °C does not double the volume, doubling 298 K does.
Worked example
How many moles are in 18 g of water (M = 18.015 g/mol)?
Pick the Moles from mass member.
n = m / M = 18 ÷ 18.015 = 0.999 mol.
The board also shows that this is 6.016×10²³ molecules.
How to use it
Pick the formula or topic from the dropdown.
Fill the fields that appear, keeping units consistent (L not mL, K not °C).
Leave one box blank where the tool solves for it (ideal gas law).
Read the result and the substituted formula under the board.
Share the link — it remembers the member and your numbers.
Frequently asked questions
How do I calculate moles from grams?
Divide the mass by the molar mass: n = m/M. For 18 g of water, n = 18 ÷ 18.015 ≈ 0.999 mol. The molar mass comes from summing atomic weights on the periodic table.
Where do I get the molar mass?
From the periodic table: multiply each atomic weight by how many atoms of that element appear, then add. H₂O = 2(1.008) + 15.999 = 18.015 g/mol; CO₂ = 12.01 + 2(16.00) = 44.01 g/mol. This page deliberately treats molar mass as an input rather than parsing formulas.
What is molarity?
Moles of solute per liter of solution: M = n/V. Half a mole of NaCl dissolved to a final volume of 2 L is 0.25 M. Note it is liters of the whole solution, not liters of solvent added.
How does the dilution equation work?
C₁V₁ = C₂V₂ — moles of solute are unchanged when you add solvent. Diluting 100 mL of 2 M stock to 500 mL gives C₂ = 2 × 100/500 = 0.4 M, a 5× dilution.
Why must gas temperatures be in kelvin?
Because the gas laws are proportional to absolute temperature. Charles’s law with 25 °C and 50 °C would not double the volume, but 298 K and 596 K do. Convert first: K = °C + 273.15.
What does the pH scale mean?
pH = −log₁₀ of the hydrogen ion concentration, so each whole step is a 10× change. 0.001 M acid has pH 3; pure water is 10⁻⁷ M, pH 7; and pH + pOH = 14 in water at 25 °C.