Conservation of mass Flashcards
What atom are the masses of all other atoms relatively compared to
Carbon-12
How does the Ar take isotopes into account
Because it is the mean relative mass of the atom
How does one calculate the relative formula mass of a compound
Add up the relative atomic mass of all of the elements within it
Chlorine has 2 isotopes, Cl35 (with a percentage abundance of 75%) and Cl37 (with a percentage abundance of 25%)
What is chlorine’s Ar
((35x75)+(37x25))/100
=35.5
Chlorine has 2 isotopes, Cl35 (with a percentage abundance of 75%) and Cl37 (with a percentage abundance of 25%)
What is chlorine’s Ar
(35x75) + (37x25)
————————— = 35.5
100
What is the Mr of CO2
12 + (16 x 2) = 44
How does one calculate the number of moles in:
A) an element
B) a compound
A) mass
———
Ar
B) mass
———
Mr
How are balanced equations more accurate than non-balanced equations
Whereas unbalanced equations only show reactants and products of a reaction, a balanced equation shows the amount of atoms, molecules OR ions in a reaction
What is shown to us in terms of atoms, molecules or ions in the equation:
2Mg + O2 —> 2MgO
2 atoms of magnesium react with one molecule of oxygen to form 2 magnesium ions and 2 oxide ions
How many moles are in 80g of magnesium oxide
80g divided by (24 + 16) = 2
If you have 5g of magnesium in the equation:
2Mg + O2 —> 2MgO
What mass of magnesium oxide do you have?
(2x24) = 48g magnesium
(2x40) = 80g magnesium oxide
Moles x Ar
1g of magnesium gives (80 over 48)g of magnesium oxide
5 x (80 over 48)g = 8.33g of MgO
What values can be gained from a balanced symbol equation
Masses of reactants and products
What is the percentage of nitrogen in:
(NH4)2SO4
Ar of N = 14
14 x 2 = 28
Total Mr of compound = 132
28/132 x 100 = 21.2%(3sf)
what is the equation for percentage by mass
what is the equation for percentage of an element in a compound
Mass of element/Total Mr of compound x 100
