Question

You are in space and running out of water. You do have a great deal Of magnesium carbonate pentahydrate. It is possible to extract the water from this. Determine the percent of water by mass in the hydrate magnesium carbonate pentahydrate (MgC03 • 5H20). If your answer is 17%. enter 17. do not put in the percent sign. As an introduction to his class, Severus Snape teaches the first years at Hogwarts about hydrates. He begins with equations representing various dehydrations. Which of the following equations properly represents the dehydration Of magnesium carbonate pentahydrate (MgCOa • 5H20)?

a. MgCO₃ • H₂O heat> MgCO₃ + H₂O
b. MgCO₃ • 5H₂O MgCO₃ + 5H₂O
c. MgCO₃ • 5H₂O MgCO₃ + H₂O
d. MgCO₃ • 5H₂O MgCO₃ + 5H₂O

Answer 1

The percent of water by mass in magnesium carbonate pentahydrate (MgCO3 · 5H2O) is 51.7%. The correct dehydration equation is MgCO3 · 5H2O → MgCO3 + 5H2O.

Step-by-step explanation:

To determine the percent of water by mass in magnesium carbonate pentahydrate (MgCO3 · 5H2O), you must calculate the total mass of water (5 moles of H2O) and divide it by the molar mass of the entire compound.

• Molar mass of water (H2O) = 18.015 g/mol
• Molar mass of magnesium carbonate (MgCO3) = 84.31 g/mol
• Molar mass of hydrate = 84.31 g/mol (MgCO3) + 5 × 18.015 g/mol (H2O) = 174.385 g/mol
• Mass of water in hydrate = 5 × 18.015 g/mol = 90.075 g
• Percent of water = (90.075 g / 174.385 g/mol) × 100% = 51.7%

The correct dehydration equation for magnesium carbonate pentahydrate is:

MgCO3 · 5H2O → MgCO3 + 5H2O