Chapter 2 - Amount of Substance Flashcards
What is a mole and why is it useful?
A mole is the number of particles of one element or compound multiplied by Avogadros Constant. It is useful because it is a completely transferrable unit, and one mole of a substance will always contain the same number of entities no matter what it is.
What is the difference between relative atomic mass and relative molecular mass
Ar is the average weighted mass of an atom of an element compared to 1/12th carbon-12 whereas Mr is the mass of a molecule relative to 1/12th of carbon - 12
What is the equation which links concentration, moles and volume?
Concentration (mol dm^-3) = moles / volume (dm^3)
What equation links mass, moles and Mr?
Mass (g) = moles x Mr
what is the ideal gas equation?
pV = nRT
pressure (Pa) x Volume(m^3) = moles x gas constant (given) (J K^-1 mol^-1) x Temperature (k)
What is empirical formula
The simplest whole number ratio of the number of each element in a compound, unlike molecular formula which is the actual number present
What is the relation between molecular and empirical formula
If given composition by mass or percentage by mass the empirical mass can be used to calculate the molecular mass
What is the atom economy equation
Molecular mass of desired product / sum of molecular mass of all reactants (x100)
Why are high atom economies favourable?
They are favourable because it will reduce the amount of waste products and result in higher amounts of the desired product, which is very important in being efficient with the Earth’s resources
What is the equation for percentage yield?
Real mass / observed mass x 100
Why is percentage yield important and what affects it?
Higher percentage yield means more product is gained, which reduces cost and amount of reactants used. 100% is impossible however, because side reactions will always happen, and reactants will always be left on equipment used, however human error can reduce percentage yield
