Which statement describes the way in which energy moves between a system of reacting substances and the surroundings?
A. Molecular collisions create energy that is then released into the
surroundings.
B. The potential energy of the system and its surroundings
increases.
C. Molecular collisions transfer thermal energy between the system
and its surroundings.
D. The thermal energy of the system and its surroundings increases.

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