Part 1:

Question

Find the % by mass of each element in camphor (C10H20O).

Step 1: Find the atomic mass of each element in the molecule.
Atomic Mass of C: 12.0107
Atomic Mass of H: 1.00794
Atomic Mass of O: 15.9994

Step 2: Find the mass combination of each element.
Carbon: 10 atoms 10 * 12.0107 = 120.107 g/mol
Hydrogen: 20 atoms 20 * 1.00794 = 20.1588 g/mol
Oxygen: 1 atom 1 * 15.9994 = 15.9994 g/mol

Step 3: Find the total molecular mass of the molecule.
Molecular Mass of (C10H20O) = 120.107 g/mol + 20.1588 g/mol + 15.9994 g/mol = 156.2652 g/mol

Step 4: Find the mass percent composition of each element.
Mass percent composition of C=(Mass Contribution of C)/(Molecular Mass ofC10H20O)*100%
=(120.107 g/mol)/(156.2652 g/mol)*100%
=0.76861002961 * 100%
=76.86%

Mass percent composition of H=(Mass Contribution of H)/(Molecular Mass ofC10H20O)*100%
=(20.1588 g/mol)/(156.2652 g/mol)*100%
=0.12900377051 * 100%
=12.90%

Mass percent composition of O=(Mass Contribution of O)/(Molecular Mass ofC10H20O)*100%
=(15.9994 g/mol)/(156.2652 g/mol)*100%
=0.10238619987 * 100%
=10.24%

%C = 76.86%
%H =12.90%
%O = 10.24%

Part 2
What is the mass of oxygen (in grams) present in 1.0 pound (454 grams) of camphor?

I was able to answer all of part 1 but I am not sure how to continue and answer part 2.

Answer 1

You have 454 g camphor.
mass %O in camphor is 10.24% so
454 x 0.1024 = ? g O