How does a chemist know the amount of reactants to use and the amount
of products they will obtain?

Asample of the male sex hormone testosterone, c19h28o2, contains 3.88×10^21 atoms of hydrogen.(a) how many atoms of carbon does it contain? (b) how many molecules of testosterone does it contain? (c) how many moles of testosterone does it contain? (d) what is the mass of this sample in grams?

What are transitions between a liquid and a solid called? identify which way they are transitioning

How many moles of al3+ ions are in 1.25 moles of al2o3