[brandnewrocks13]

So I tried this problem and am doing something wrong.  Here is the question:


During the discharge of an alkaline battery, 11.0 g of Zn are consumed at the anode of the battery.  What mass of MnO2 is reduced at the cathode during this discharge.

So I came up with this redox rx:

Zn(s) + MnO2(s) + 4H+ --> Zn2+ + Mn2+ +2H20

then I tried to use the stoichiometry to go from grams Zn to grams MnO4
I set it up like this:
(11.0 g Zn)*(1 mol Zn)/(65.39 g Zn)*(1 mol MnO2)/(1mol Zn)*(86.938 g MnO2)/(1 mol MnO2) 


the answer i came out with was 14.6 g, which isn't the right answer on my online hw.  I just am not sure what i'm doing right.  Can someone help me out please! 

[Borek]

Check if you have correct products.

[brandnewrocks13]

how do i know if i have the right products? 
I just looked on a standard reduction potentials chart that i've been using for my class and it listed those equations.

[macman104]

Equation is correct, but your molar masses are incorrect (well at least 1).

Err...sorry, I read magnesium not manganese.

[brandnewrocks13]

i figured it out.. I justed needed to have a 2:1 ratio for the MnO2 and zinc.  I must've had my equation wrong, but I got it to work out.  thanks for the help

[macman104]

i figured it out.. I justed needed to have a 2:1 ratio for the MnO2 and zinc.  I must've had my equation wrong, but I got it to work out.  thanks for the help

Time to take mac back to school, because I can't understand why you would need a 2:1 ratio...

[Borek]

http://en.wikipedia.org/wiki/Alkaline_battery