Use the atomic weights of H and Cl to calculate the answer to question 7. For H, it is 1. For Cl it is 35.45.
The ratio of H to Cl in HCL is 1:1. Therefore, 16.2 grams of H means that there will be 16.2 * 35.45 grams of Cl within the resulting HCl. Therefore, the grams of HCl will be 16.2 grams + 574.29 grams = 590.5 grams of HCl