What is the total amount of heat, in joules, required to completely vaporize a 50.0-gram sample of liquid water at its boiling point at standard pressure

To get the total amount of heat or the energy required we will get it from this formula:
Q= M L 
when M= the mass of the substance =50 g
and L= the specific latent heat of vaporization 
and when the latent heat of vaporization is defined as the energy required to change the state of the substance from the liquid to gas phase, and here for water, we can assume it as 2258 j/g.
So by substitution:
Q = 50 * 2258 = 112900 J