Amounts of Substances: Equations Flashcards
Number of Particles
• N = n x L
- N = number of particles
- n = number of moles (mol)
- L = Avogadro’s constant (6.022 x 10^23)
• Amount of substance is measured using moles
- One mole is roughly 6.022 x 10^23 particles (Avogadro’s constant)
- These particles can be anything: atoms, molecules, ions etc.
Number of Moles (Mass)
• n = m / Ar or Mr
- n = number of moles (mol)
- m = mass (g)
- Ar or Mr = relative / molecular mass (g mol^-1)
Density
• density = m / V
- Density (g cm^-3)
- m = mass (g)
- V = volume (cm^3)
Number of Moles (Concentration)
• n = C x V
- n = number of moles
- C = concentration (mol dm^-3)
- V = volume (dm^3)
Ideal Gas Equation
• PV = nRT
- P = pressure (Pa)
- V = volume (m^3)
- n = number of moles (mol)
- R = gas constant (8.31 JK^-1mol^-1)
- T = temperature (K)
Molecular Formula
Molecular formula = Empirical formula x (Mr / Mr of Empirical formula)
% Yield
% yield = (actual yield / theoretical yield) x 100
- Theoretical yield is calculated by using reacting masses
% Atom Economy (Mass)
% atom economy = (total mass of desired product / total mass of all products) x 100
% Atom Economy (Mr)
% atom economy = (Mr of useful product x balancing number / Sum of all Mr x balancing number for all reactants) x 100
Moles of Gas
• At room temperature and pressure, one mole of any gas occupies the same volume (24dm^3)
- Volume = amount in mol × molar volume
- Moles of gas = gas volume / volume of 1 mole
- Mol = Volume (24dm^3) / 24
- Rtp = 25° C and 1 atmosphere
Calculating Empirical Formula
• Empirical formula is the simplest whole number ratio of atoms of each element in a compound
- Divide mass or % by Ar
- Simplify this ratio by dividing all the answers by smallest
- Find a whole number ratio
- Write the empirical formula
