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Flashcards in Moles Calculations Deck (11):
1

What is the mass number?

Total number of protons and neutrons in an atom

2

What are isotopes?

Atoms of the same element that have the same number of protons but different numbers of neutrons

3

What is the relative atomic mass?

The average mass of isotopes of an element compared to the mass of a Carbon-12 atom

4

How to work out RAM

²⁴Mg = 77.6%
²⁵Mg = 10.1%
²⁶Mg = 11.3%
(24 x 78.6) + (25 x 10.1) + (26 x 11.3) / 100

5

How do you calculate relative formula mass?

NH₃ = N + (Hx3) = 14 + 3 = 17

6

How to calculate percentage abundance

total mass of element in compound / RFM of compound x 100

7

How to calculate mole calculations using relative atomic mass and relative formula mass

mass = number of moles x RFM

8

If the molecular formula is H₂O₂, what is the empirical formula?

HO

9

How to work out the empirical formula from the mass of each element in a compound

• Determine the mass or percentage of elements.
• Divide the given mass or percentage by their RAM.
• Calculate the ratio of the atoms by dividing by smallest value.
Ca Br
20 80
20/40 80/80
0.5 1
0.5/0.5 1/0.5
1 : 2
CaBr₂

10

How to work out volume with moles

• volume = moles x 24(dm³)
• volume = moles x 24000(cm³)

11

What is the atomic number?

The number of protons in an atom