C4.1 - Relative atomic Masses And Moles (Finished) Flashcards
What atom is used as a reference for comparing the masses of other atoms (relative formula mass)?
Carbon - 12
How do you find out the relative atomic mass of an element?
It is the top number above the element on the periodic table.
16 O
8
16
What is one mole of any substance?
An ammount of the substance that contains an Avogadro number of particles
How do you work out relative formula mass Ar of a compound?
By adding up the relative atomic masses of the elements in it, in the ratio shown by its formula
What is the symbol for:
- Relative atomic mass
- Relative formula mass
- Ar
- Mr
What is the Mr of H2SO4?
(12) + 32 + (164) = 98
What is the Avogadro constant?
6.02 * 10^23
What is the formula to calculate moles from masses?
No. of moles = mass(g) / Ar or Mr
What is the formula to calculate masses from moles?
Mass (g) = moles * Ar or Mr
What is one mole of any substance?
It is the amount of that substance (in g) that contains an Avogadro number of particles (6.02 * 10^23)
Why do some relative atomic masses have decimal places?
As Ar is the mean relative mass of isotopes of an element
What is the relative formula mass of a compound?
The relative atomic masses of all the atoms in the molecular formula added together
How do you calculate % mass of an element in a compound?
(Ar * no of atoms of that element) / mr of compound *100
What does one mole of a substance weigh in grams?
That substance’s Ar. E.g. Carbon-12 has an Ar of 12 and a mole of it weighs 12g
