Question

When 68.0 g of a compound was burned in a bomb calorimeter that contained 0.376 kg of water, the temperature rise of the water in the calorimeter was 51.0°C. If the heat of combustion of the compound is 1,573 kJ/mol, what is the molar mass of the compound? Specific heat of water is 4.184 J/g°C. Answer to 0 decimal places and enter the units.

a. 163 g/mol
b. 140 g/mol
c. 124 g/mol
d. 98 g/mol

Answer 1

The molar mass of the compound is 1368 g/mol.

Step-by-step explanation:

To calculate the molar mass of the compound, we need to use the equation q = mCΔT, where q is the heat energy transferred, m is the mass of the water, C is the specific heat of water, and ΔT is the change in temperature. First, we need to convert the mass of water to grams: 0.376 kg × 1000 g/kg = 376 g. Using the equation, we can find the heat energy transferred: q = (376 g)(4.184 J/g°C)(51.0°C) = 78199.6 J. Now, we can convert the heat energy to kilojoules: 78199.6 J ÷ 1000 = 78.1996 kJ. Next, we can calculate the number of moles of the compound burned using the heat of combustion: 78.1996 kJ ÷ 1573 kJ/mol = 0.0497 mol. Finally, to find the molar mass, we divide the mass of the compound burned by the number of moles: 68.0 g ÷ 0.0497 mol = 1368 g/mol.