A 8.22-g sample of solid calcium reacted in excess fluorine gas to give a 16-g sample of pure solid CaF2. The heat given off in this reaction was 251 kJ at constant pressure. Given this information, what is the enthalpy of formation of CaF2(s)

The enthalpy of formation of CaF₂ is -1224.4 kJ.

Explanation:

The enthalpy of formation of CaF₂ can be calculated as follows:

Where:

q: is the heat liberated in the reaction = -251 kJ

The number of moles of CaF₂ is:

Where:

m: is the mass of CaF₂ = 16 g

M: is the molar mass of CaF₂ = 78.07 g/mol

Now, the enthalpy of formation of CaF₂ is:

Therefore, the enthalpy of formation of CaF₂ is -1224.4 kJ.

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the correct answer to this question is 2