In testing the effectiveness of an antacid compound, 20.0g of Hydrochloric Acid is mixed with 28.0g of Magnesium Hydroxide. will the base neutralize all of the acid? How much of which substance is in excess?

2HCL + Mg (OH) 2 - -> MgCl2 + 2H2O

The base will neutralize all of the acid. There will remain 12.0 grams of Mg (OH) 2 in excess.

Explanation:

Step 1: Data given

Mass of Hydrochloric acid (HCl) = 20.0 grams

Mass of Magnesium hydroxide (Mg (OH) 2)

Molar mass of HCl = 36.46 g/mol

Molar mass of Mg (OH) 2 = 58.32 g/mol

Step 2: The balanced equation

2HCL + Mg (OH) 2 → MgCl2 + 2H2O

Step 3: Calculate moles of HCl

Moles HCl = 20.00 grams / 36.46 g/mol

Moles HCl = 0.5485

Step 4: Calculate moles of Mg (OH) 2

Moles Mg (OH) 2 = 28.00 grams / 58.32 g/mol

Moles Mg (OH) 2 = 0.4801 moles

Step 5: Determine the limiting reactant

For 2 moles HCl we need 1 mol of Mg (OH) 2 to produce 1 mol of MgCl2 and 2 moles of H2O

HCl is the limiting reactant. It will completely be consumed (0.5485 moles).

Mg (OH) 2 is in excess. There will react 0.5485/2 = 0.27425 moles

There will remain 0.4801 - 0.27425 = 0.20585‬ moles of Mg (OH) 2

Remaining mass of Mg (OH) 2 = 0.20585 moles * 58.32 g/mol = 12.0 grams

The base will neutralize all of the acid. There will remain 12.0 grams of Mg (OH) 2 in excess.