Question

The mass in grams of chromium in a 25.9 gram sample of Cr 2o3 is:

Answer 1

We have to do a dimensional analysis. We have to convert from 25.9 grams of Cr2O3 to moles using the molar mass of Cr2O3 which is 152 g/mol (You can find the molar mass using the periodic table). Then, we have that in 1 mol of Cr2O3, there are 2 moles of chromium (Cr) and finally, the value that we obtain is converted to grams of Cr using the molar mass of Cr which is 52 g/mol.

This dimensional analysis would look like this:

`25.9gCr_2O_3\cdot\frac{1\text{ mol }Cr_2O_3}{152\text{ g }Cr_2O_3}\cdot\frac{2\text{ moles }Cr}{1\text{ mol }Cr_2O_3}\cdot\frac{52\text{ g Cr}}{1\text{ mol Cr}}=17.721\text{ g Cr}\approx17.7\text{ g Cr.}`

The answer is that the mass of chromium is 17.7 grams.