Moles & Chemical Calculations Flashcards
Define atomic mass
It is the number of protons and neutrons in the nucleus of an atom. it is the top number
Define relative atomic mass (RAM a Ar)
The average mass of the Natalie occurring isotopes of the element relative to the mass of carbon 12 atom.
Relative molecular mass, MR (RMM)/relative formula mass (RFM)
The mass of a molecule of the compound relative to the mass of an atom of carbon 12. Found by adding to the top numbers of each atom
Define isotopes
Atoms of the same element which have the same number of protons but different number of neutrons.
Define relative isotopic mass
The mass of the isotopic of an element relative
Define a mole
The amount of substance that has the same number of particles (atoms, molecules, ions etc) as there are in exactly 12 g of carbon 12 (6.0 23 X 10^23)
Define molar mass
The mass of one mole of a compound is, expressed in grams. Thus mole of carbon 12 has a mass of exactly 12 g. One mole of sodium-23 has a mass of 23 g and so on
Define Avogadro’s number
The number of particles in one mole eg 6.0 23 X 10^23
Find the RFM/RMM of magnesium carbonate. What would you find and how would you do it?
You would simply add up all of the relative atomic masses which are the top numbers on the periodic table
How do you work out percentage by mass
% mass = RMM of element / RMM of compound x 100
What is relative formula mass the same as
Relative molecular mass, Mr
How do you work out the number of moles
Mass divided by Mr
How do you work out the average mass of two isotopes
You times the percentage (make sure is zero point) and then times it by the top number
What steps do you use to work out a reacting maths question
- Work out any moles you can
- Compare molar ratio and determine the moles
- Workout what you were asked for in the question
How do you work out the percentage yield
Percentage yield = how much product we actually obtained/how much product we should have obtained (theoretical amount) x 100
