How much heat is needed to completely boil 85.0 grams of water at 100.0 degrees Celsius?

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Answer 1 · 2018-05-06T14:26:39

#191.87# kilojoules

We use the latent heat formula, which states that,

#q=mL#

where:

#m# is the mass of the substance

#L# is the latent heat of the substance, in this case it is the latent heat of vaporization

#L_f# of water is #40.65 \ "kJ/mol"#. So, we might as well convert the mass of water into moles for easier calculations.

Here, we got:

#(85color(red)cancelcolor(black) "g")/(18.01528color(red)cancelcolor(black)"g""/mol")~~4.72 \ "mol"#

So, the energy needed is:

#q=4.72color(red)cancelcolor(black)"mol"*(40.65 \ "kJ")/(color(red)cancelcolor(black)"mol")#

#=191.87 \ "kJ"#