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May 4, 2016

# Homework Help: Chem 100

Posted by Kristin on Sunday, May 1, 2011 at 4:49pm.

at 1 atm how much energy is required to heat 67 grams of H2O(s) at -22 degrees C to H2O(g) at 159 degrees C
• Chem 100 - DrBob222, Sunday, May 1, 2011 at 5:46pm

q1 = heat to move ice at -22 to the melting point of zero C.
q1 = mass x specific heat ice x (Tfinal-Tinital)

q2 = heat to convert solid water (ice) at zero C to liquid water at zero C.
q2 = mass x heat fusion.

q3 = heat to move liquid water at zero C to the boiling point at 100 C.
q3 = mass x specific heat water x (Tfinal-Titial)

q4 = heat to convert liquid water at 100 C to steam at 100 C.
q4 = mass water x heat vaporization

q5 = heat to move steam at 100 C to steam at 158 C.
q5 = mass x specific heat steam x (Tfinal-Tinitial)

Total Q = q1 + q2 + q3 + q4 + q5.
Notice that you have only two formulas to memorize. One is for changing phase (at melting and boiling points); the other is with the same phase (from -22 to zero)(from zero to 100) (from 100 to 158). That should keep things simple for you.