What is the percent by mass of oxygen in Cr(NO3)3?

To calculate the percent by mass of oxygen in Cr(NO3)3, we need to consider the molar mass of each element. Cr(NO3)3 consists of one chromium atom, three nitrogen atoms, and nine oxygen atoms. The molar mass of Cr(NO3)3 is 274.06 g/mol. The molar mass of just the oxygen atoms in Cr(NO3)3 is 144.00 g/mol. Therefore, the percent by mass of oxygen in Cr(NO3)3 can be calculated as (144.00 g/mol / 274.06 g/mol) x 100%.