Answer:
Go to your periodic table and look for each element. Find the mass for Aluminum, Nitrogen, Oxygen, and Hydrogen.
After you find those, for each compound you must add them together and find the least amount of sig figs after the decimal point.
For the first compound, Al(NO3)3, you will have a total of
1 Aluminum atom
3 Nitrogen atoms
9 Oxygen atoms
Aluminum has 26.982 g/mol
Nitrogen has 14.007 g/mol
Oxygen has 15.999 g/mol
Now multiply those numbers by the amount of atoms of each element.
(1)26.982 g/mol = 26.982 g/mol
(3)14.007 g/mol = 42.021 g/mol
(9)15.999 g/mol = 143.991 g/mol
now add all of those numbers together, and you see that their least significant figure after the decimal is 3, so round to 3 digits after the decimal point.
26.983 + 42.021 + 143.991 = 212.994
now do the same for the other compound
to start you off.. you have
6 Hydrogen atoms
3 Oxygen atoms
Hydrogen has 1.009 g/mol
Oxygen has 15.999 g/mol
the least significant figure after the decimal point is 3, so round you 3 digits after the decimal point.
after you finish getting your totals, you. until them and find the greatest sig fig over all. comment on this if you need further instruction :)
