Question

How many grams of magnesium metal will react completely with 5.2 liters of 4.0 M HCl? Show all of the work needed to solve this problem.
Mg (s) + 2HCl (aq) MgCl2 (aq) + H2 (g)

Answer 1

Answer:
mass = 242.372 grams

Explanation:
1- getting the number of moles of HCl:
molarity = number of moles of solute / liters of solution
4 = number of moles of HCl / 5.2
number of moles of HCl = 4 * 5.2 = 20.8 moles

2- getting the number moles of magnesium:
From the balanced equation given, we can note that one mole of magnesium is required to react with two moles of HCl. To get the number of moles required to react with 20.8 moles of HCl. we will simply do cross multiplication as follows:
1 mole of Mg ...............> 2 moles of HCl
?? moles of Mg ...........> 20.8 moles of HCl
Number of moles of Mg = 20.8 / 2 = 10.4 moles

3- getting the mass of Mg:
number of moles = mass / molar mass
Using the periodic table, we can find that the molar mass of magnesium is 24.305 grams.
This means that:
10.4 = mass / 24.305
mass = 24.305 * 10.4
mass = 242.372 grams

Hope this helps :)