MatSc 503: Solutions to HW #5
1.
The general reaction for desulfurization from molten iron to slag can be written as
[S] in Fe
«
[S] in slag
The order of reaction(n) is decided based on what value of ’n’ satisfies the equation,
dS
dt
kS
Fe
Fe
n
[]
.[ ]
=
( )
where ’k’ is the reaction rate constant. Negative sign implies that concentration of sulfur
in slag decreases with time.
For each value of ’n’, change in sulfur concentration with time is given by a different
equation.
n = 0;
n = 1;
ln
n = 2;
.
.
Sk
t
A
t
B
S
kt
C
Fe
Fe
Fe
+
+
=+
1
where A,B, C are integration constants. By obtaining the best fit for the data using the
above equations, we can find the order of reaction in both cases(with and without Si).
From the correlation coefficient obtained from fit (not shown here), it is clear that both
reactions are first order. This means that Si increases the rate constant of the
desulfurization reaction. It can be verified by comparing the rate constants from the
equation of best fit.
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 Spring '02
 CHEN
 Physical chemistry, Partial Pressure, Vapor pressure, Vapor

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