A tank in a room at 19°C is initially open to the atmosphere on a day when the barometric pressure is 102 kPa. A block of dry ice (solid CO₂) with a mass of 15.7 kg is dropped into the tank, which is then sealed. The reading on the tank pressure gauge initially rises very quickly, then much more slowly, eventually reaching a value of 3.27 MPa. Assume T_final = 19°C. 

(a) How many moles of air were in the tank initially? Neglect the volume occupied by CO₂ in the solid state, and assume that a negligible amount of CO₂ escapes prior to the sealing of the tank. 

(b) Estimate the percentage error made by neglecting the volume of the block of dry ice placed in the tank. (The specific gravity of solid carbon dioxide is approximately 1.56.) 

(c) What is the final density (g/L) of the gas in the tank? 

(d) Explain the observed variation of pressure with time. More specifically, what is happening in the tank during the initial rapid pressure increase and during the later slow pressure increase?