Stoichiometry

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​BCA tables are means to calculate stoichiometry of a reaction.

We need a BALANCED reaction to do a BCA table.

BCA table is always in terms of Moles.​ So have to convert to moles.

B - Before: What is given.

C - Change: Reactants is -, Products is +, linked by mole ratio

A - After: B+C​

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​This refers to REACTANTS only.

Limiting reagent is the reactant that RUNS OUT in a reaction.

Excess reagent is still LEFT OVER after the reaction.

You can use the BCA table to determine what remains and what runs out.​

e.g. what would 6 moles of NaHCO₃ yield?​

​ 2 NaHCO₃ → Na₂CO₃ + CO₂ + H₂O

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Consider reaction: N₂ + 3H₂ --> 2NH₃

If we start with 2 moles of N2 and 3 moles of H2, complete BCA table.​

What is the limiting and excess reactants?​

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Look at BCA table below for​

N₂ + 3H₂ --> 2NH₃

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Limiting Reactant = H₂ (runs out or is 0 After)

Excess Reactant = N₂ (4 moles are left)​

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