This question asks to find the number of molecules of an acid to an appropriate number of sig figs.
The data they give you is the mass is 38.25g and molar mass is 150.
The calcaulation is (38.25/150) * 6.02x10^23.
Since the mass is given to 4 sig figs and the other two are exact values, I put my answer in 4 sig figs. But the MS says it has to be in 3 sig figs due to one value being at 3 sig figs? Plz help