Chemistry · Acids and Bases
pH and pOH Calculator
Convert between pH, pOH, [H⁺] and [OH⁻]. Visual scale and pH of everyday substances.
Open toolChemistry calculators for the periodic table, stoichiometry, equation balancing, pH, molarity, dilution, gases, oxidation numbers, thermochemistry and Ksp.
Chemistry with step-by-step solutions
Chemistry Tools for High School and University Entrance Exams
Chemistry calculators for the periodic table, stoichiometry, equation balancing, pH, molarity, dilution, gases, oxidation numbers, thermochemistry and Ksp.
Chemistry
Periodic Table
Complete interactive periodic table. Data for each element, electron configuration and charts.
Open toolChemistry
Stoichiometry Calculator
Stoichiometry with step-by-step solutions. Mass, moles and volume at STP with purity and yield.
Open toolChemistry
Chemical Equation Balancer
Balance chemical equations automatically. Per-atom verification and minimal coefficients.
Open toolChemistry · Solutions
Molarity Calculator
Molar concentration, moles, molar mass and solution volume.
Open toolChemistry · Solutions
Dilution Calculator
Use C1·V1 = C2·V2 to prepare and compare diluted solutions.
Open toolChemistry · Gases
Ideal Gas Calculator
Calculate pressure, volume, temperature and amount of substance with PV = nRT.
Open toolChemistry · Redox
Oxidation Number Calculator
Oxidation number in simple compounds and ions from the sum of the oxidation numbers.
Open toolChemistry · Thermochemistry
Thermochemistry Calculator
Enthalpy, heat of reaction and identification of exothermic or endothermic processes.
Open toolChemistry · Equilibrium
Solubility and Ksp
Solubility product, molar solubility and precipitation tendency.
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Articles and study paths
Use these routes as study guides. They connect theory, examples and related tools.
How to do stoichiometry
Learn to use mole ratios, mass, volume at STP, purity and yield.
Balancing chemical equations
See how to check atoms before and after the reaction.
pH and pOH without memorizing
Relate pH, pOH, H⁺ and OH⁻ ions to the acid-base scale.
Oxidation numbers in compounds and ions
Use the sum of oxidation numbers to solve simple compounds.
Solved exercises
Exercise 1
What is the molarity of 0.5 mol in 2 L of solution?
M = n/V = 0.5/2 = 0.25 mol/L.
Practice with the toolExercise 2
If pH = 3, what is the pOH at 25 °C?
pH + pOH = 14. So pOH = 14 − 3 = 11.
Practice with the toolExercise 3
In PV = nRT, why must the temperature be in Kelvin?
Because the ideal gas equation uses an absolute scale. Convert with K = °C + 273.15.
Practice with the toolCommon mistakes in Chemistry
- Doing stoichiometry without balancing the equation first.
- Using volume in mL when the formula requires liters.
- Plugging a Celsius temperature into the ideal gas equation.
- Confusing a low pH with a basic solution; a low pH means higher acidity.
Recommended pairings
To study better, follow these pairs of tools: