CHEMISTRY COMMUNITY

Hi!
In question Self-Test E.2A I am trouble figuring out which number of significant figures to use.
Question: The mass of a copper coin is 3.20g. Suppose it were pure copper. (a) How many moles of Cu atoms would the coin contain, given a molar mass of Cu of 63.55 g/mol? (b) How many Cu atoms are present?
How many significant figures would I use in my answers and why?

You would use 3 sig figs. You always use the least amount of sig figs from the figures involved in your calculations for your final answer!

Right. Since 3.20 has the least number of sig figs based on the original problem, your final answer should have three sig figs as well. Hope this helps!

A resource that I found extremely helpful when it came to my sig fig questions can be found on Dr. Lavelle's website. It's titled "Everything you want to know about Sig Fig" and is located under Course Materials. Good luck!