Ask, understand and practise chemistry
Choose a supported model, review units and assumptions, inspect the worked solution, then practise independently. These tools calculate on your device. They do not claim complete curriculum coverage or KICD approval.
Read an element, then explain its place
Atomic number counts protons. A neutral atom has the same number of electrons. Isotopes have the same proton count but different neutron counts. A standard atomic weight describes normal materials, often as an interval; it is not an isotope mass number.
Before this: Whole numbers and positive/negative charge
Conserve atoms without changing formulae
Chemical balancing changes coefficients in front of species. Subscripts stay fixed because changing them changes the substance. Each element, and charge for explicit ionic species, must have the same total on both sides.
Before this: Chemical symbols and formula subscripts
Build molar mass from the formula
Count each element, including atoms inside repeated groups and hydrates. Multiply counts by the cited abridged atomic weights and add the contributions. Molar mass is mass per mole; its classroom unit here is g mol⁻¹.
Before this: Multiplication and chemical formulae
Connect mass, moles and particles
Amount of substance n is measured in moles. Use n=m/M for mass and N=nNₐ for a count of specified entities. The Avogadro constant is exactly 6.02214076×10²³ mol⁻¹. State whether the entities are atoms, molecules or formula units.
Before this: Molar mass and division
Find the limiting reactant
Divide each available reactant amount in moles by its balanced coefficient. The smallest ratio determines reaction extent. Multiply that extent by the product coefficient to obtain theoretical product moles.
Before this: Balanced equations and moles
Virtual educational models only. Laboratory demonstrations require qualified supervision and appropriate safety controls. Advanced topics are added only after verification.