Formulae, Stoichiometry and Mole Concept (Writing Equations, Mole Concept and Chemical Calculations)

Equationso Balanced

A balanced equation is when there is an equal number of atoms of each element on both sides of the equation

o Ionic An ionic equation shows the ions taking part in a reaction and the products

formed, while leaving out the spectator ions that do not react Relative mass

o Atomic It is the number of times the mass of one atom of an element is greater than

1/12 of the mass of one carbon-12 isotope It is the average mass of one atom as compared to 1/12 the mass of a carbon-12

isotopeo Molecular

It is the average mass of a molecule compared to 1/12 the mass of one atom of carbon-12 isotope

It is the sum of the relative Ars of the component elementso Percentage

Percentagemass of anelement∈acompound= Ar of element×numberof atoms∈formulaMr of thecompound

×100%

Formulaso Empirical

It is the simplest formula of the compound It shows the types of elements present It shows the simplest ration of the atoms

o Molecular It shows the exact number of atoms of each element in a molecule Can be found using empirical formula and Mr of compound

Avogadro’so Law

Equal volumes of all gases, under the same temperature and pressure contain the same number of molecules (moles)

One mole of gas occupies 24 dm3 of space at rtp. of 25OC and 1 atmo Constant

In a mole of a substance there are 6×1023 particles (atoms, molecules E.G.) Stoichiometry

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o It is the relationship between the amounts of reactants and products involved in a chemical reaction

o It is the finding the moles of reactant and products using given informationo E.G. Dividing mass by Mr, Dividing vol. of gas by 24

Limiting reactiono Limiting reagent

It determines the amounts of products formed, as it limits it.o Excess regent

The is that reactant that is not completely used up Concentration

o It is the amount of a solute (either mass or mole) dissolved in a unit volume of the solution

o 1 dm3 = 1000 cm3

% yield and purityo % yield

Actual yield

Theoretical yield×100%

o % purity

Amount of pure subst ance

Amopunt of substance used∈reaction×100%

Nickolas Teo