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Equation 3 · Part 6 · How Chemical Dynamics and Catalysis Actually Work

subscript

SF=ξi/∑jξjS_F = \xi_i / \sum_j \xi_j
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

When a reaction can plausibly form more than one product — partial versus complete oxidation, a straight-chain versus branched hydrocarbon, hydrogen versus oxygen evolution as a side reaction — “selectivity” names which pathway wins, and IUPAC defines it with no vocabulary that presumes anything about the catalyst’s intent: fractional selectivity for a given product is the extent-of-reaction rate toward that product divided by the sum of rates toward all products, SFS_F = ξi\xi_i / ∑j\sum_j ξj\xi_j , and relative selectivity between two products is simply the ratio of their two rates [ 2 ] . Selectivity is therefore a kinetic competition among simultaneous pathways, decided by which transition state…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.