CHEMISTRY COMMUNITY

Should you ever round molar mass from the periodic table based on sig figs or should you always use the given number without rounding?

For calculations, use the given molar mass on the periodic table without rounding. Round based on the amount of sig figs at the end of your calculation.

You can use the full number if you want as long as your final answer is with the correct number of sig figs. Or you can round to the number of sig figs in the problem and then solve, but I think the first way will get you a more accurate answer.

I believe that the TAs are grading the exams are based on the least amount of sig figs stated in the problem. So it is safe to assume that you should use the given values of molar mass on the periodic table and then do the correct number of sig figs as your final answer.