So, if a sample of a compound decomposed to its constituent elements and produced 25.6 g of o, and 9.60 g of carbon, and another sample produced 21.6 g of o, how much carbon was produced in the second sample?

Method 1:
First find out the formula of the sample.
no. of moles of O = 25.6/16 = 1.6
no. of moles of C = 9.6/12 = 0.8
ratio of C:O = 1:2
formula is CO2

In the second sample,
no. of moles of O = 21.6/16 = 1.35
no. of moles of C = 1.35/2 = 0.675
mass of C = 0.675 x12 = 8.1g

method 2:
Actually it’s quite simple. The two samples are the same compound so the elements produced should be in the same ratio.
C/9.6 = 21.6/25.6
C = 8.1g

Enzyme make a hormone as a catalyst

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.