Help with ap chem redox equation?

Question

Cr2O7-2 + Cl-  Cr+3 + Cl2

a. What are the oxidation numbers for Cr and O in Cr2O7-2

b. Which reactant is being oxidized?

c. If the redox reaction occurs in ACID, please balance the equation out. Show all half reactions and electron transfer

d. If the redox reaction occurs in BASE, please write out the final net ionic equation

e. If 34.12 mL of 0.2 M of Cr2O7-2 is reacted with 24.15 mL of Cl-, what is the molarity of Cl- solution if the titration were done in ACID?

Answer 1

a. Cr => +6 and O = -2

b. Cl goes from -1 to 0 and it is oxidized

c.

Cr2O72-  + 14 H+  ++ 6e->> 2 Cr3+ + 7H2O

2Cl- >> Cl2 + 2e-

Cr2O72- + 14 H+ + 6 Cl- >> 2 Cr3+ + 3 Cl2 + 7H2O ( acidic solution)

d.

Cr2O72- + 7H2O + 6Cl- >> 2 Cr3+ + 3Cl2 + 14 OH- ( basic solution)

e.moles Cr2O72- = 0.03412 x 0.2= 0.006824

moles Cl- = 6 x 0.006824 = 0.04094

M = 0.04094 / 0.02415 L =  1.70 M