Suppose you need to prepare 122.4 mL of a 0.233 M aqueous solution of NaCl. What mass of NaCl do you need to use to make the 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?