A chemist performs the reaction 6ClO_2 + 3H_2O -> 5HClO_3 + HCl. If a chemist wants to make 50.0 g of HClO_3, what is the minimum number of grams of ClO_2 that she can use?

1 Answer
Apr 21, 2018

Well, "chlorine dioxide" DISPROPORTIONATES....and I make it mass of UNDER 50*g with respect to ClO_2.

Explanation:

ClO_2 is oxidized to HClO_3:

stackrel(IV)ClO_2(aq) +H_2O(l)rarr Hstackrel(V)ClO_3(aq)+H^+ +e^(-) (i)

And ClO_2 is reduced to Cl^(-):

stackrel(IV)ClO_2(aq)+4H^+ +5e^(-)rarr Cl^(-)+2H_2O(l) (ii)

And for both half-equations, mass and charge are conserved. And so we take 5xx(i)+(ii) to get....

5ClO_2(aq)+ClO_2(aq)+4H^+ +5e^(-) +5H_2O(l)rarr 5HClO_3(aq)+Cl^(-)+2H_2O(l)+5H^+ +5e^(-)

And we cancel common reagents....

5ClO_2(aq)+ClO_2(aq) +3H_2O(l)rarr 5HClO_3(aq)+Cl^(-)+H^+

...or...

6ClO_2(aq) +3H_2O(l)rarr HCl(aq)+5HClO_3(aq)

The which I think is balanced with respect to mass and charge.

And so (finally!) we want a molar quantity with respect to "chloric acid"..of (50.0*g)/(84.46*g*mol^-1)=0.592*mol..

And so with respect to ClO_2 we needs 6/5*"equiv" ...

i.e. 6/5xx0.592*molxx67.45*g*mol^-1=??*g