Question

If the masses of cr and o are in the ratio of 13:12 in cro3 then the ratio of o that combines with the same mass of cr in cr2 o3 and cr2o7

Answer 1

Answer:

The ratio therefore is 3:7.

Answer 2

Answer:

3:7

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.

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