# Stoichiometry: How to find the Limiting Reagent?

## Mg + 2HCl → MgCl₂+ H₂ What volume of hydrogen 100kPa, 25℃, is produced from the reaction of 50.0g of Mg and the equivalent of 75g of HCl?

May 20, 2018

The question should not be in the organic section....

#### Explanation:

$M g \left(s\right) + 2 H C l \left(a q\right) \rightarrow M g C {l}_{2} \left(g\right) + {H}_{2} \left(g\right) \uparrow$

And this is a redox reaction. What is oxidized, and what is reduced?

$\text{Moles of metal} = \frac{50.0 \cdot g}{24.3 \cdot g \cdot m o {l}^{-} 1} = 2.06 \cdot m o l$...

$\text{Moles of acid} = \frac{75.0 \cdot g}{36.5 \cdot g \cdot m o {l}^{-} 1} = 2.06 \cdot m o l$...

Given the stoichiometry, CLEARLY, there is insufficient acid to effect complete oxidation....and the METAL is the reagent in excess, and the acid is the reagent in deficiency...

At most, we could make HALF an equiv with respect to dihydrogen gas...and since the molar volume under these conditions is $24.8 \cdot L \cdot m o {l}^{-} 1$ (I think...), the volume of dihydrogen is....

24.8*L*mol^-1xx1.03*mol=??*L