Amount of Substance Flashcards
Define relative atomic mass, Ar.
Average mass of on element of an atom / 1/12 mass of carbon-12
Define relative molecular mass, Mr.
Average mass of one molecule / 1/12 mass of carbon-12
How do you find relative molecular mass?
Add up all of the relative atomic masses.
What is Mr when referring to ionic compounds?
Relative formula mass.
What is a mole?
6.022 x 10^23 particles
Why is the Avagadro’s constant this number?
Number of atoms in 12g of carbon-12.
What is the molar mass?
Mass per mole of unit substance.
The relative atomic mass of any element in grams contains how many atoms?
1 mole.
number of moles = ?
Mass / Mr
What does a solution consist of?
A solvent with a solute dissolved in it.
What does the concentration of a solution tell us?
How much solute is present in a known volume of solution.
What is the equation for concentration in moldm^-3?
Number of moles / volume (dm^3)
How do you convert from cm^3 to dm^3?
x10-3
What is the ideal gas equation?
PV = nRT
What is P and what is it measured in?
Pressure, Pa.
What is V and what is it measured in?
Volume, m^3.
What is n and what is it measured in?
Number of moles, moles.
What is R and what is it and what is it measured in?
The ideal gas constant, 8.31 JK^-1mol^-1.
The same number of moles of any gas has the same what under the same pressure and temperature?
Volume.
Define empirical formula.
The formula that represents the simplest whole number ratio of the atoms of each element preset in the compound.
Give an example of an empirical formula.
CO2.
What is the first step in finding the empirical formula?
Find the masses of each element present in the compound.
What is the second step in finding the empirical formula of a compound?
Find moles, moles = mass/Mr.
What is the last step in finding the empirical formula of a compound?
Divide every value by the smallest number, use this as ratio.
What is the molecular formula?
The formula that gives the actual number of molecules in a compound.
How do you find the number of units of the empirical formula in the molecular formula?
Divide the relative molecular mass by the relative mass of the empirical formula.
What is a spectator ion?
They don’t take part in the reaction.
What is the equation for percentage atom economy?
(mass of desired product / total mass of reactants) x 100
What does the atom economy tell us?
How many atoms in a reaction must be wasted in theory.
What does the yield tell us?
How much is lost, the practical efficiency.
What are conditions that cause loss?
Impure reactants, reversible reactions, side reactions, incomplete reactions, practical losses.
Equation for yield?
(Grams of product obtained / theoretical max) x 100
