The reaction equation is:
CaF₂ + H₂SO₄ → 2HF + CaSO₄
The molar ratio between fluorite and hydrogen fluoride is 1 : 1.
The moles of fluorite supplied are:
Moles = 15.6 / 78.07
Moles = 0.200
The moles of hydrogen fluoride produced will be 0.2.
Now, we may use the ideal gas equation to determine the temperature:
PV = nRT
T = PV/nR
T = (899 * 7.4) / (0.2 * 62.36)
T = 533.40 K
The temperature will be 260.25 °C