The reaction of dichromate (Cr2O 2−

7

) with hydrogen ions (H

+

)

and ferrous ions (Fe2+

) is given by the reaction x1Cr2O 2−

7 + x2Fe2+ + x3H

+ −→ x4Cr3+ + x5Fe3+ + x6H2O.

We have to determine the unknown coefficients x1, · · · , x6.

a. By requiring that the reaction has the same number of Cr atoms on both sides of the equation, write down an equation for x1 and x4

b. Do the same for O, Fe and H to get three more equations.

c. Finally, write down the equation that says the charge must be the same on both sides of the equation.

d. Write the system of equations in matrix form.

e. Use Wolfram Alpha to solve this system of equations, and write down two possible solutions.

f. Write down all the possible solutions. Which solution has the smallest integers?