calculate the heat energy released when 25.8 g of liquid mercury at 25 C is converted to solid mercury at its melting point.
Constants for mercury at 1 atm:
heat capacity of Hg-->28.0
melting point-->234.32 K
enthalpy of fusion-->2.29 kj/mol
q1 = heat released moving T from 298 to m.p.
q1 = mass Hg x specific heat Hg x (Tfinal-Tinitial)
q2 = heat released by freezing
q2 = mass Hg x heat fusion(convert enthalpy fusion from kJ/mol to J/g OR change grams Hg to mols and kJ to J.
To calculate the heat energy released when liquid mercury at 25°C is converted to solid mercury at its melting point, we need to use the equation:
q = m * ΔHf
Where:
q is the heat energy released
m is the mass of the substance
ΔHf is the enthalpy of fusion
First, we need to convert the given mass of mercury from grams to moles. To do this, we will use the molar mass of mercury, which is 200.59 g/mol.
molar mass of Hg = 200.59 g/mol
moles of Hg = mass of Hg / molar mass of Hg
moles of Hg = 25.8 g / 200.59 g/mol
Next, we'll find the number of moles of mercury:
moles of Hg = 0.1286 mol
Now, we can calculate the heat energy released:
q = m * ΔHf
We know that the enthalpy of fusion, ΔHf, is given in kilojoules per mole. To convert it to joules per mole, we multiply it by 1000:
ΔHf = 2.29 kJ/mol = 2.29 * 1000 J/mol = 2290 J/mol
Finally, we can calculate the heat energy released:
q = 0.1286 mol * 2290 J/mol
Therefore, the heat energy released when 25.8 g of liquid mercury at 25°C is converted to solid mercury at its melting point is approximately 294.9 joules.