limiting reagent

[rinsterman12]

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if 340 grams of silvernitrate and 285g of Mag chloride are allowed to react, how many grams of AgCl are produced?

2 AgNO3 + MgCL2 ----> 2 AgCl + Mg(NO3)2

How is MgCL2 the limting reagent? You get two moles of AgNO3 and three moles of MgCL2? It seems to me that the AgNO3 will run out before the MgCL2 will? Please help.......

 

[MCAT4life]

well you need to find the molar equivalent for each first to find your LR. On these more difficult LR problems.

340 grams AgNO3 / 170 gram per mole AgNo3 = 2 moles.
285 grams MgCl2 / 94 gram per mole MgCl2 = 3 mole (ish)

now This is from TBR which I think is great.

If Reactant A (AgNO3) to Reactant B (MgCl2) ratio 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 is less, than A is limiting reagent.

2/3 is less than 2/1 (therefore AgNO3) is limiting reagent.

If you don't understand/don't want to remember the rule, you can see that in the balanced equation you have 2:1 ratio which means that for every mole of MgCl2 you need 2 moles of AgNo3, so for every 3 moles of MgCl2 you would need 6 moles of AgNo3, which from what what have gotten your AgNO3 is clearly lacking, therefore it is used up first.

Hmm i don't see where you got MgCl2 as LR from... what book was this from?