Based on the balanced reaction 4cr+3o2=2cr2o3 how many grams of cr (mm=52.00g/mol) will react with 5.10x10^2 grams of o2 (mm=32.00g/mol) in complete
scientific notation

Grams of Cr that react are 11,05x10*2 g

Explanation:

4Cr  +  3O2 → 2Cr2O3

This equation means that 4 moles of Cr, react with 3 moles of O2.

My mass of O2 is 5,1x10*2g but I need to know the moles.

Mass/ Molar mass = Moles

5,1x10*2g /32.00g/mol = 15,9 moles of O2

So the rule of three is

If 3 moles of O2 __ react with __ 4 moles of Cr

15, 9 moles of O2 ___ react with___ ?

(15,9 . 4) /3 = 21,2 moles of Cr.

To know the mass, I have to multipply, the molar mass  to the moles.

Molar mass . Moles = Mass

52g/mol . 21,2 moles = 1105 gr.

In scientific notation I can write 11,05x10*2 g