Question

A 0.1149-g sample of solid magnesium is burned in a bomb calorimeter that has a heat capacity of 1769 J/°C. The calorimeter contains exactly 321 g of water, and the temperature increases by 1.126°C. Calculate the heat given off by the burning Mg, in kJ/g and in kJ/mol.

Answer 1

The heat given off by the burning Mg is 30.5 kJ/grams or 745.5 kJ/mol

Step-by-step explanation:

Step 1: Data given

Mass of magnesium sample = 0.1149 grams

Molar mass of magnesium = 24.3 g/mol

bomb calorimeter that has a heat capacity of 1769 J/°C

Mass of water = 321 grams

Temperature change = 1.126 °C

Step 2: Calculated heat released

Q = (1769 J/°C * 1.126 °C) + (321 grams * 4.184 J/g°C * 1.126 °C)

Q = 3504.18 J =3.504 kJ

Step 3: Calculate the heat given off by the burning Mg, in kJ/g

3.504 kJ / 0.1149 grams = 30.5 kJ/grams

Step 4: Calculate moles of Magnesium

Moles of magnesium = mass magnesium / Molar mass magnesium

Moles magnesium = 0.1149 grams / 24.3 g/mol

Moles magnesium = 0.0047 moles

Step 5: Calculate the heat given off by the burning Mg, in kJ/mol

3.504 kJ / 0.0047 moles = 745.5 kJ/mol

The heat given off by the burning Mg is 30.5 kJ/grams or 745.5 kJ/mol