3.1.2 Amount of Substance Flashcards
Ar = ?
Average mass of one atom of an element / 1/12 the mass of one atom of 12-C
Mr = ?
Average mass of one molecule / 1/12 the mass of one atom of 12-C
What does Ar stand for?
Relative atomic mass.
What does Mr stand for?
Relative molecular mass or relative formula mass.
How to find relative formula mass?
Sum of all the Ars of the atoms present.
What is the Avagadro constant the same as?
Number of particles in a mole.
What is the Avagadro constant and where does it come from?
6.022 x 10^23, number of atoms in 12g of 12-C.
moles = ?
mass / Mr
What does the concentration of a solution tell us, what are the units?
How much solute is present in a known volume of solution, moldm^-3.
What is the equation for moles using concentration?
moles = concentration x volume / 1000
What is the ideal gas equation?
PV = nRT
Define empirical formula.
The empirical formula represents the simplest whole number ratio of the atoms of each element present in a compound.
What are the steps to finding the empirical formula?
1) Find masses of each element
2) Find no. of moles of atoms of each element, moles = mass / Mr
3) Convert into a whole number ratio
Define molecular formula.
The actual number of atoms of each element in a compound.
How do you find the molecular formula?
Relative molecular mass / relative mass of empirical formula
What do ionic equations do?
Simplify the equation by considering the ions present.
What are spectator ions?
Ions that cancel out on both sides of an ionic equation.
% atom economy = ?
(mass of a desired product / total mass of reactants) x 100
What does % atom economy tell us in theory?
How many atoms must be wasted in a reaction.
What does yield tell us?
The practical efficiency of the process, how much is lost by the practical process or reactions that don’t go to completion.
Yield = ?
(no. of moles of product / theoretical moles of product) x 100
OR
(grams of product / theoretical max grams) x 100
Why do ionic compounds have high m.ps?
Oppositely charged ions, strong attraction between ions.
When finding % atom economy from an equation what values do we take?
The Mrs.
When doing calculations what do you need to double check?
All values are correct and SI, know what compound the mole value is attached to.
Conversion from cm^3 to m^3?
x10^-6
