To calculate the error percentage in molar mass, you need to first determine the actual molar mass and the experimental molar mass. The error percentage is then calculated using the following formula:
Error % = |(experimental - actual) / actual| x 100%
For example, let's say the actual molar mass of a compound is 100 g/mol, and the experimental molar mass determined in the lab is 95 g/mol. The error percentage would be:
Error % = |(95 - 100) / 100| x 100%
Error % = |-0.05| x 100%
Error % = 5%
Therefore, the error percentage in molar mass is 5%