Amount Of Substance Flashcards
Why are relative masses are used ?
The masses of atoms and molecules measured in grams are too small to be used easily so for this reason relative masses are used
What did scientists used to compare all atoms and molecules to the mass of ?
Scientists used to compare all atoms and molecules to the mass of hydrogen which is one rounded to the nearest whole number -scientists now compare all atoms and molecules with the mass of the carbon -12 isotope
What is 1g equal to?
One twelfth the mass of carbon 12 atom is exactly one gram without having to round so it’s now used by chemists
Define relative atomic mass
The relative atomic mass At is the weighted average mass of an atom of an element taking into account its naturally occur in isotopes relative to 1/12 the relative atomic mass of an atom of carbon 12
Relative atomic mass equation
Average mass of one atom of an element /1/12 mass of one atom of carbon12
Average mass of one atom of an element x12/mass of one atom of carbon 12
Define relative molecular mass
The relative molecular mass mr of a molecule is the mass of that molecule compared to 1/12 the relative atomic mass of an atom of carbon 12
Equation of relative molecular mass
Average mass of one molecule/1/12 mass of one atom of carbon 12
Average mass of one molecule x12/mass of one atom of carbon 12
Why is relative formula mass used for ionic compounds
They don’t exist as molecules has the symbol mr
Equation for percentage mass of an element
At of elementary school x no of its atoms/mr of compound. X100
What is the avogadros constant
The atoms in 12g of carbon 12
What is a mole?
Amount of substance that contains 6.022 x 10 23
What is the relative atomic mass of any element?
In grams contains one mole of atins
How do you calculate moles ?
Number of Moles= mass(g)/mass of one mole (g)
What attraction is between polar molecules?
Permanent dipole dipole attraction eg HCL
What is a polar bond?
Covalent bonding which the boiling points of electrons are equally shared and there’s a separation of charge between one end and the other
