McDalton Professional Edition

This is a freeware computer program, designed for professional use. In this program the uncertainty in the calculated molar mass is given as the absolute maximum error of the result. The calculated uncertainty is always rounded up to one significant figure. It is rounded up because otherwise it may occur as underestimated. Then the molar mass is rounded to the same absolute accuracy as given in the rounded uncertainty. An example will make this clear. The molar mass for PbO is calculated as 207.2 + 15.9994 = 223.1994 and the uncertainty in the molar mass is calculated as 0.1 + 0.0003 = 0.1003. The only significant figure in the uncertainty is the first Decimal and therefore molar mass is given as 223.2