Question

2.00 mL of a 12.00 M HCL solution was reacted with 0.0450 grams of magnesium.?

Answer 1

Answer:

Magnesium Mg will be the limiting reagent .

Explanation:

The limiting reagent is one that is first consumed in its entirety, determining the amount of product in the reaction. When the limiting reagent ends, the chemical reaction will stop.

In other words, the limiting reagent is that reagent that is consumed first in a chemical reaction, determining the amount of products obtained. The reaction depends on the limiting reagent, because the other reagents will not react when one is consumed.

In this case, the balanced reaction is:

Mg + 2 HCl ⇒ MgCl₂ + H₂

You know tha 2.00 mL of a 12.00 M HCl solution was reacted with 0.0450 grams of magnesium.

Being Molarity (M) the number of moles of solute that are dissolved in a certain volume, calculated by the expression:

$Molarity=\frac{number of moles of solute}{volume}$  ( Molarity is expressed in units $\frac{moles}{liter}$)

then the number of moles can be calculated as:

number of moles of solute=molarity* volume

So, being:

• molarity= 12 M
• volume= 2 mL= 0.002 L (being 1,000 mL= 1 L)

The number of moles of HCl that react is:

number of moles of HCl= 12 M*0.002 L= 0.024

On the other hand, since the molar mass of magnesium is 24.305 g / mol, then if 0.0450 grams of magnesium react, it indicates that they must react:

$0.0450 grams*\frac{1 mol}{24.305 grams} = 0.00185 moles$

To determine the limiting reagent, it is possible to use the reaction stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), and a simple rule of three as follows: if by stoichiometry 1 mole of Mg reacts with 2 moles of HCl, how much moles of Mg will be needed if 0.024 moles of HCl react?

$moles of Mg=\frac{0.024 moles of HCl*1 moles of Mg}{2 moles of HCl}$

moles of Mg= 0.012

But 0.012 moles of Mg are not available, 0.00185 moles are available. Since you have less moles than you need to react with 0.024 moles of HCl, magnesium Mg will be the limiting reagent .