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## Homework Statement

(a)How much heat must be added to a block of 0.120kg of frozen ammonia initially at 100

^{o}C to convert it to a gas at 80

^{o}C given the following information?

(b) assuming this could be done using a reversible process what would be the total entropy change associated with this operation given that ΔS=∫dQ/T (from b to a where b= T

_{i}and a=T

_{f}

T melt = -78 C

Tvap = -33 C

c solid = 2030

Lf = 332000

C liquid = 4750

Lv=1370000

c, gas = 28

M = 17.0 g/mol

## Homework Equations

ΔS=∫dQ/T

## The Attempt at a Solution

I've figured out the first part the heat added is simply 2.36 x 10

^{5}J

But I can't seem to get the second part analyzing the integral:

$$ ΔS= \int_{173.15K}^{353.15K}\frac {dQ} T \ $$

where $$ dQ = mcdT $$

by integrating the function I get:

$$ ΔS =0.120kg * 4750J/kgK *( ln(353.15) - ln(173.15)) $$

I get ~ 400 J/K as an answer and the actual answer is 865 J/K ... I don't get what I'm doing wrong, is this the right path to take or am I actually suppose to take the integral from init Temp to melting point temp then from melting point temp to vaporization temp then to 80

^{o}C ?