A balanced reaction relates several changing inventories. Reaction extent provides one progress variable against which all of those changes can be compared.
Keep the signed reaction coefficients
For a specified reaction, a species amount change equals its signed stoichiometric coefficient multiplied by the change in reaction extent. Reactants have negative coefficients and products have positive ones. The coefficient convention belongs with the reaction as written. Primary reference.
Compare a fictional change vector
Use the constructed reaction 2A + B → 3P. A progress increment of 0.100 mol implies changes of −0.200 mol A, −0.100 mol B and +0.300 mol P. Dividing each change by its signed coefficient gives the same 0.100 mol increment.
If a recorded product increase were instead 0.240 mol while those reactant changes stayed the same, its inferred increment would be 0.080 mol. The records would not fit the single written reaction without further explanation. Different recovery boundaries, side reactions or an inconsistent measurement basis could warrant investigation.
Check what the balance can establish
Construct an original balance table containing initial amount, final amount, signed coefficient and coefficient-normalized change. Preserve whether each amount describes the whole batch or only a sampled or recovered fraction. A common progress value cannot be checked by comparing unmatched populations.
This is a consistency model, not proof of reaction completion or an approved batch procedure. A limiting-reactant calculation predicts an upper bound; this guide instead asks whether several observed species changes can share one reaction-progress variable. Keep the observations available before interpreting a mismatch.
Solution review worksheet
This blank worksheet is for your own project. It contains no H M machine trial result.
| Question | Record to retain |
|---|---|
| What reaction is assumed? | Balanced equation with signed coefficients |
| Which inventory does each amount cover? | Whole batch, sample or recovery boundary |
| Do changes imply one progress value? | Species change divided by its signed coefficient |
Customer Questions
What is the fictional product increase?
0.300 mol for a 0.100 mol extent increment.
What extent follows from a 0.240 mol product increase?
0.080 mol for the stated product coefficient.
Does a mismatch identify its cause?
No. It identifies a balance question requiring additional evidence.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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