A student, adds 136.92 g of sucrose (FW = 342.31) to exactly 400.0 mL of dH2O. The total solution volume increased to 420.0 mL after the sucrose was dissolved and the solution was thoroughly mixed. What is the molarity of the final solution?

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?