A formula that relates the amount of a substance to a mass?

Explanation:

A formula mass of substance is a sum of the average atomics masses of each atom represented in the chemical formula and is expressed in atomic mass units.the formula mass of covalent compound is also called the molecular mass

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"