quantitative chemistry

empirical formula definition

the simplest whole number ratio of atoms of elements in a compound

-written when talking about giant structures

-molecular formula used when talking about molecules

Standard solution

Solution with a know concentration

What is percentage yield an why might you not get 100% yield?

-actual yield/ theoretical yield x 100

-100% yield is when all reactants have been converted into products

-this doesn't happen due to:

 -reaction not being complete

 -reaction in reversible

 -some product is lost during purification

atom economy

-the percentage of atoms in a chemical equation that ends up in the desired product

-mass of atoms in desired product/ mass of all atoms in reactant OR products x 100

-higher atom economy = fewer waste materials

relative atomic mass

-Ar

-the average mass of all isotopes of an element compared to 1/12th of the mass of one atom of carbon-12

What's the definition of a mole and what's avogardo's constant?

-the amount of a substance containing the same number of particles as their are atoms in exactly 12g of carbon-12

-avogadro's consatant is the number of particles found in one mole of a substance

-6.02x10^23

molar mass

-the mass of one mole of a substance

-same as Mr

-measured in gmol^-1

molar volume

-the volume of one mole of gas at a specified room temperature and pressure

-measured in dm^3/mol

-1 mole of gas occupies 24dm^3 at room temp and pressure (RTP)

-10cm in 1dm

-1000cm^3 in 1dm^3

water of crystallisation

-water pesent in crystals of a certain compound/ water molecules embedded between ions of salt

-water in chemically combined in stiochiomentric amounts, usually by dative covalent or ionic-dipole forces

-water is easily expelled by heating

-x.H20 represents the number of waters of crystallisation

percentage composition

-describes proportions of different elements in a compound

percentage error in an element

absolute error/measured value x 100

equation for concentration

-concentration = mol/vol (dm^3)

-mol = vol x conc

-moldm^-3 or M

hydroscopic meaning

-able to absorb water from the surroundings

What's the equation for pressure volume temperature moles and gas constant?

pV=nRT

-pressure (Pa or N/m^2) x volume (m^3) = moles x gas constant x temperature (K)

-to convert degrees C to kelvin, add 273

-to convert dm^ to m^3, divide by 1000, there are 10dm in 1m

when making a salt, why is the solvent left to evaporate, not boiled off

prevents anhydrous salt forming

doesn’t have x.H2O