Is it possible for something with more mass to be lighter than something with less mass?

Yes, depending on the context.

If the more massive object is located in an environment that either provides an upward force or has less downward acceleration, then it may exert less force in the downward direction (weigh less) than an object with less mass.

Examples:

1. a 110 kg object weighed under water may show less weight than a 100 kg object weighed in air—particularly if it is much less dense.*

2. a man of mass 80 kg weighed on Earth's moon will definitely show less weight than a 100 kg man weighed on Earth.

* Actually, density has an effect on weight anytime the weighing is done in a medium other than a vacuum. (This is a potential source of error when trying to calibrate scales to very high accuracy.) When weighing is done in water, for example, an object of sufficiently low density will float, so show no weight at all.

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