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This Microsoft Excel spreadsheet (file AB.xls) uses a primitive
differential equation solver to determine the concentration of
A and B as a function of time for a simple reaction A = B. The
reaction is first order in the forward (A --> B) and reverse
direction (B --> A). The parameters that can be adjusted are:
- the initial concentration of A, [A]o found in
cell B2
- the initial concentration of B, [B]o found in
cell C2
- the rate of the forward (A --> B) reaction kAB found in
cell D2
- the rate of the reverse (B --> A) reaction kBA found in
cell E2
The output of note consists of the:
- initial ratio of B to A, [B]o /[A]o
found in cell F2
- the final ratio of B to A, found in cell G2
- a graph of [A] and [B] vs. time
The rate constant in the forward (kAB) and the reverse direction
(kBA) can be adjusted in the range: 0-6. The initial concentration
of A and B should fall in the range 0-1.
The following are suggested conditions that you should investigate.
- Keep kAB = kBA and vary the initial concentrations of [A]o
and [B]o to determine how these initial concentrations
affect the final ratio, [B]/[A] and the time it takes to achieve
this ratio.
- Keep [A]o and [B]o constant and vary
kAB and kBA to determine how these changes affect the final ratio,
[B]/[A] and the time it takes to achieve this ratio.
- Vary the rate constants and initial concentrations and try
to determine some general rules for predicting the final [B]/[A]
ratio and the time it takes to achieve this ratio.
Reaction Rate and Equilibrium | Origin of Life | ChemConnections