Mrs. Andrews did a science demonstration with dry ice. First, she placed some dry ice inside of a balloon. Then she tied off the ballon and placed it on a triple beam balance. The balance showed that the combined mass of the balloon and dry ice was 22 grams. While the balloon sat on the balance, it began to expand. As the dry ice sublimed, or changed from a solid into a gas, the gas filled the balloon. When the dry ice had sublimated completely, how much mass was sitting on the balance and why?