During a chemical reaction, a fixed amount of Iron combines completely with a fixed amount of oxygen to form Iron oxide. Which statement best describes the mass of the iron odide that is produced?
a)The mass is equal to the mass of the Iron minus the mass of the oxygen before reacting.
B)The mass is equal to the mass of the Iron plus the mass of the oxygen.
C)The mass is greater than the combined mass of both the Iron and the oxygen
D)The mass is less than the mass of the Iron but greater than the mass of the oxygen before reacting.

the answer to this question is 3.

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o