Question

14. Calculate the mass of Chromium in each of
the following oxides (1) Cro. (2) Cr2O3.(3)
CrO3. Given mass of O=16u. mass of
Chromium=52u*​

Answer 1

Step-by-step explanation:

First we will use a mass of oxygen of 12 g.

The reaction of oxygen and Chromium to from dichromate CrO7 is

2Cr+7O2 → 2CrO7

Mole ratio is 2:7:2

In this case 13 g of Cr will be used in this equation.

Calculating the moles of Cr (molar mass = 52)

moles = mass/molar mass

            = 13/52

            = 0.25 moles

mole ratio between Cr:O7 is 2:7

Therefore the moles of oxygen is 0.875, calculate the mass using this mole value. 

mass = moles × molar mass  

        =  0.875 × 28 = 28 g

The ratio of the oxygen in the 2 equations then is: 

12 g: 28 g 

the ratio, therefore, is 3:7