C2.6 Quantitative Chemistry Flashcards
What us relative atomic mass?
The mass of an element compared to Carbon12. Hydrogen has a Ar of .
What are the relative atomic masses of Carbon, Nitrogen and oxygen?
12, 14 and 16
What is the relative formula mass?
The total mass of all of the atoms in a compound.
What is the formula mass of H2O?
18 (H=1)*2 + 16
What is the formula mass of Ca(NO3)2?
164
Ca-1
N-2
O-6
What is the empirical formula of a substance?
The simplest whole number ratio of atoms in a substance.
How do you calculate the empirical formula?
Mass/Atomic mass.
Mass2/Atomic mass2.
Now divide both by the smaller result to give 2 whole numbers.
These are the number of atoms in the empirical formula.
What is the empirical formula of 10g of Calcium reacted with 17.8g of Chlorine?
Ca= 10g/Ar40=0.25 Cl= 17.8g/Ar35.5=0.5
0.25/0.25=1
0.5/0.25=2
So 1Ca and 2Cl = CaCl2
What is percentage composition?
The percentage of a substance that is made up of a certain element.
What is the percentage composition of Oxygen in Postassium Nitrate (KNO3)?
Ar(K) + Ar(N) + 3Ar(O)
=39 + 14 + (316)
=101
316/101100=47.5%
What is the theoretical yield?
The maximum amount of product that could theoretically be produced with a certain amount of reactants.
How do you calculate theoretical yield?
Calculate the formula masses for all substances in the balanced equations according to the balanced equations. Then add units.
What is the theoretical yield of water made from 4g of hydrogen and 32g of oxygen.
2H2 + O2 -> 2H2O
2(1+1) + (16+16) -> 2(1+1+16)
22 + 32 -> 218
4+32->36
What is percentage yield?
The actual yield compared to the theoretical yield.
How do you calculate percentage yield?
Actual yield/Theoretical yield * 100
