Chem chap 9

Make sure to know:

-construct mole ratios between any two participants -converting compounds from mass to mols and mols to mass using molar mass -determining limiting reactant and excess reactant -determine the amount of product that can form, using the theoretical yield determine percent yield and actual yield when necessary

What is the difference between limiting and excess reactants, and why is it significant to know the difference?

The limiting reactant limits the amount of products, and does not have enough to "go around" whereas excess is the left over that is not fully used in the reaction.

Ideal Stoichiometric Calculations:

Use the mole ratio between what is given (known) and what is being calculated (unknown), which always is done using moles. If given mass, convert moles first, then use the mole ratio; if mass is asked for, use the mole ratio first, then convert moles to mass.

mole ratio

a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction.

percentage yield

actual yield/theoretical yield x 100

composition stoichiometry

deals with the mass relationship of elements in compounds

Problem Type 1

given and unknown quantities in moles. [amount of given substance(mol) ---> amount of unknown substance(mol)].

Mass--> Moles

given mass x 1 mol given/given molar mass x mol unknown/ mol given = unknown substance mole.

Mass--> Mass

given mass x 1 mol given/known molar mass x mol unknown/mol given x molar mass of unknown/ 1 mol unknown = mass of unknown substance.

Moles--> Mass

given moles x mol unknown/mol given x molar mass of unknown/ 1 mol unknown =mass of unknown substance.

conversions of quantities in moles

given x conversion factor =unknown quantity ex. given moles x mol unknown/mol given =unknown mole.

Problem Type 2

given: amount of moles and unknown: mass [amount of given substance(mol)--> amount of unknown substance(mol)--> mass of unknown substance(g)].

Problem Type 3

given: mass and unknown: amount of moles [mass of a given substance(g)-->amount of given substance(mol)-->amount of unknown substance(mol)].

Problem Type 4

given: mass and unknown: mass [mass of given substance(g)-->amount of given substance(mol)-->amount of unknown substance(mol)-->mass of unknown substance(g)].

reaction stoichiometry

involves the mass relationships between products and reactants in a chemical reaction

theoretical yield

max. amount of product that can be produced from a given amount of reactant

actual yield

measured amount of product obtained from reaction

limiting reaction

reactant that limits the amount of the other reactant that can combine and the amount of product that can form in a chemical reaction.

excess reactant

substance that is not all used up in a reaction

What is the difference between composition stoichiometry and reaction stoichiometry ?

there is a mass/mol ratios of elements in compounds in composition, and mass/mole ratio of compounds in balanced equations in reaction.