The heat of fusion of a substance is 80 J/g. How much energy is required to melt 25 g of the substance?

2000J

Explanation:

Given parameters:

Heat of fusion  = 80J/g

Mass of substance = 25g

Unknown:

Amount of energy required to melt the given mass = ?

Solution:

To solve this problem, the amount of energy required to melt the substance is given as;

             H  = m L

m is the mass

L is the heat of fusion

 Insert the given parameters and solve;

           H  = 25 x 80  = 2000J

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