Consider the following reactions: NaCl + K _ 2 Cr _ 2 O _ 7 + H _ 2 SO _ 4 ~A + KHSO _ 4 + NaHSO _ 4 + H _ 2 O A + NaOH B + NaCl + H _ 2 O B + H _ 2 SO _ 4 + H _ 2 O _ 2 C + Na _ 2 SO _ 4 + H _ 2 O In the product ' C ', ' X ' is the number of O_ 2 ^ 2- units, ' Y ' is the total number oxygen atoms present and ' Z ' is the oxidation state of C r. The value of X+Y+Z is \_\_\_\_.
A. A
Reaction 1: NaCl + K_2Cr_2O_7 + H_2SO_4 CrO_2Cl_2 (A, chromyl chloride) Reaction 2: CrO_2Cl_2 + 4NaOH Na_2CrO_4 + 2NaCl + 2H_2O, B = Na_2CrO_4 Reaction 3: Na_2CrO_4 + H_2SO_4 + H_2O_2 CrO_5 + Na_2SO_4 + H_2O C = CrO_5 or CrO(O_2)_2 (chromium peroxide, blue) Structure: one oxo group and two peroxide (O_2^ 2- ) units X = number of O_2^ 2- units = 2 Y = total oxygen atoms = 5 Z = oxidation state of Cr: O^ 2- (-2) + 2 O_2^ 2- (-4) = -6, so Cr = +6 X + Y + Z = 2 + 5 + 6 = 13
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