How many cm3 would be required. Help me out. ?

Question

How many cm3 of 0.200M KClO3 will be required to react completely with 20.0 cm3 of 0.100M Cr2O3 to produce K2CrO4 and Cl-?

Answer 1

1 KClO3  (with Cl @ +5 each)  takes 6 electrons --> Cl - (with Cl @ -1 ea)

Cr2O3  (with 2 Cr+3 's)--> 2 K2CrO4 (two Cr+6) & 6 electrons lost

are balanced in electrons taken & lost:

1 KClO3  & 1 Cr2O3 --> Cl - &  K2CrO4

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find moles of Cr2O3 :

0.020 litres @ 0.100 mol / litre = 0.002 moles Cr2O3

0.002 moles Cr2O3 = 0.002 moles KClO3

0.002 moles @ 0.200 mol/ litre = 0.0100 litres

your answer is: 10.0 ml of KClO3 sol'n