Limiting Reagent (from BR)

[Silverfalcon]

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I feel like BR basically says... I didn't learn what limiting reagent was. Lol. I swore that I did.. but it basically says it's different.

The limiting reagent is the reactant that is exhausted first, not necessarily the reactant with the lowest number of moles.

What? If one reactant has the lowest number of moles, doesn't that mean that it will be exhausted first?

And here are two sentences back-to-back that I just do not get (and it's making me frustrated).

If the ratio of the moles of Reactant A to Reactant B is greater than the ratio of Reactant A to Reactant B from the balanced equation, then Reactant B is the limiting reagent. If the ratio of Reactant A to Reactant B is less than the ratio of Reactant A to Reactant B from the balanced equation, then Reactant A is the limiting reagent.

I don't get why I need to compare the ratio of moles of what are given versus moles of the balanced equation. And when it says ratio, how do you set up ratio - like, couldn't you reserve A and B and arrive at wrong conclusion? Ugh.

 

[fizzgig]

you can have 2x + 1y -> products, as your balanced equation but either can be the limiting reagent.

start with 4mols x and 4 mols y, x is limiting.
start with 4mols x and 1 mol y, y is limiting.

the balanced equation coeffs are only half the story.

 

[Silverfalcon]

you can have 2x + 1y -> products, as your balanced equation but either can be the limiting reagent.

start with 4mols x and 4 mols y, x is limiting.
start with 4mols x and 1 mol y, y is limiting.

the balanced equation coeffs are only half the story.

Thank you - that makes much more sense. 👍