Mole Calculations Flashcards
Equation: for number of moles in an element
Number of moles =
Number of moles n = mass / RAM
The mass of 1 mole of an element is equal to
The Relative atomic mass RAM of the element
Top number on the periodic table
Define empirical formula
The simplest ratio of atoms of each element in a compound
Example
Hydrogen peroxide - empirical formula is HO
Molecular formula is H2O2
Find the empirical formula of a compound containing 1.04g of chromium Cr and 0.48g of oxygen O.
RAM of Cr = 52g
RAM of O = 16g
Cr. O
1.04/52 0.48/16
=0.02 =0.03
Cr2 O3
Find the empirical formula of a compound containing 54.9% of potassium K and 45.1% of oxygen O.
RAM of K = 39g
RAM of O = 16g
K O
54.9/39 45.1/16
=1.41 =2.82
=1 =2
K O2
Equation: for number of moles in an compound
Number of moles =
Number of moles n = mass/ relative formula mass
The mass of 1 mole of a compound is equal to
The relative formula mass RFM
Calculate the relative formula mass of methane CH4
RAM of C = 12
RAM of H = 1
12 x 4x1
= 16
Define Molecular formula
The actual number of atoms of each element in a single molecule.
Example
Hydrogen peroxide - empirical formula is HO
Molecular formula is H2O2
The molecular formula for hydrogen peroxide is H2O2.
What is the empirical formula for hydrogen peroxide?
HO
What is ‘water of crystallisation’?
When ionic compounds incorporate water in their structure.
A substance incorporating water in its structure is said to be hydrated. If heated the water is driven off as steam and the substance formed is said to be …
Anhydrous
One mole of any substance contains the same number of atoms or molecules. This number is
602300000000000000000000
= 6.023 x 10?
Percentage yield =
Percentage yield = mass of substance formed / theoretical max mass. X 100%
The empirical formula for ethane is NO2
The Molecular formula for NO2 can be found by..
Empirical mass of NO2= 14 + 16 +16 = 46
Formula or molecular mass of NO2 = 92
92/46 = 2
So molecular formula is N2O4
