Using the ideal gas law, the number of moles SO2 is equal to PV/RT, or pressure times volume divided by the gas constant and temperature. This is 14.5*1.1/((2.5+279.15)*.082), or 0.66 moles. Since one mole CaSO3 is consumed for every mole SO2 generated, 0.66 moles of CaSO3 are consumed. CaSO3 has a molar mass of 40+32+16*3=120 grams, so .66 moles of CaSO3 is equal to 80 grams, our final answer.
