C4 Chemical Calculations Flashcards
Number of moles =
Mass (g) / Mr
How are the masses of atoms compared?
By measuring them relative to atoms of carbon-12
Avogadro constant =
6.02x10^23
Total mass of reactants =
Total mass of products
Limiting reactant
The reactant that gets used up first-not in excess
The amounts of product formed in a chemical reaction are determined by
The limiting reactant
Percentage yield =
(Actual mass of product produced / maximum theoretical mass of product possible) x 100%
Yield of a chemical reaction
The mass of product that a chemical reaction produces
Factors affecting percentage yield
Product being left behind in the apparatus, reactants may not be pure, losses in separating the products from the reaction mixture, reversible reactions not going to completion and some reactants may produce unexpected reactions
Percentage atom economy =
(Relative formula mass of desired product from equation / sum of the relative formula masses of the reactants from equation) x 100%
Atom economy
A measure of the extent to which the atoms in the starting materials (the reactants) end up in the desired product. Any remaining atoms end up in other products
1dm^3 =
1000cm^3
Concentration (g/dm^3) =
Amount of solute (g) / volume of solution (dm^3)
How can you increase the concentration of an aqueous solution?
Adding more solute and disolving it in the same volume of its solution. Evaporating off some of the water from the solution so you have the same mass of solute in a smaller mass of solution.
Titration
A technique used to measure accurately what volumes of acid and alkali react together completely
