How long will it take to synthesize 10^-4 mol/L of the iodoketone starting with 0.5 mol/L of ketone and 0.001 mol/L of I2, if the H concentration is held constant at 0.1 mol/L

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?