3: Amount of substance Flashcards
Module 2
Definition of a mole
A mole of a substance is the amount of that substance that contains the same number of elementary particles as there are carbon atoms in 12.00000 grams of carbon-12.
Grams of 1 mole of carbon-12, Hydrogen, Hydrogen molecule and sodium chloride
One mole of carbon-12 has a mass of 12.0g.
One mole of hydrogen atoms has a mass of 1.0g.
One mole of hydrogen molecules has a mass of 2.0g. (as their are 2 hydrogen atoms because it is H2 so the Mr is 2)
One mole of sodium chloride has a mass of 58.5g. (As the symbol is NaCl)
What is avogadro’s number?
The number of particles in one mole of a substance is 6.02 x 1023. This is known as Avogadro’s number,Na
How do you calculate the number of particles of a substance?
The number of particles can be calculated by multiplying the number of moles by Avogadro’s number.
The number of moles can be calculated by dividing the number of particles by Avogadro’s number.
**(Number of particles) = (number of moles) x 6.02x10^23 **
What is molar mass?
Molar mass= The mass of one mole of a substance
And has units of gmol^-1
It must be distinguished from relative atomic/molecular/formula mass, which is a ratio and hence has no units, although both have the same numerical value.
The symbol for molar mass of compounds or molecular elements is mr. The symbol for molar mass of atoms is ar.
Equation for: Mass (m), molar mass (mr or ar) and number of moles (n)
MASS = MOLAR MASS X NUMBER OF MOLES
or m = mr x n
n=m/mr
Mass must be measured in grams and molar mass in gmol-1.
or: number of moles= mass/molar mass
What is meant by the term actual yield?
The amount of product obtained from a reaction.
What is meant by the term amount of substance?
The quantity whose unit of the mole, used as a means of counting any pecies such as atoms, ions and molecules.
What is meant by the term Avogadro constant NA?
The number of atoms per mole of the carbon-12 isotope. (6.02 × 1023
mol–1)
What is meant by the term empirical formula?
The formula that shows the simplest whole-number ratio of atoms of each element present in a compound.
What is meant by the term mole?
The amount of any substance containing as many elementary particles as there are carbon
atoms in exactly 12 g of the carbon-12 isotope, that is, 6.02 × 1023 particles.
What is meant by the term molar mass?
The mass per mole of a substance, in units of g mol–1
What is meant by the term molecular formula?
A formula that shows the number and type of atoms of each element present
in a molecule.
What is the molar gas volume
The volume occupied by one mole of any gas a constant temperature and pressure
This is 24 at rtp
Formula for number of moles of a gas
n= V/Vm
n = number of moles of gas (mol)
V = volume of gas (dm3)
Vm = molar volume (dm3 mol-1)
Ideal gas equation
pV = nRT
Atom economy equation
M of desired product / Sum of M of all reactants
x100
Percentage yield equation
Actual yield/Theoretical yield x100
