pig

jess,

you're pretty close. you've got the molar (stiochiometric) ratios of Zn to I2 correct... Those are 1:1. However, don't forget that solid Iodine is diatomic (ie. it's I2 not I), so your reaction will look something like:

Zn + I2 => ZnI2.

Did you also recover the solid zinc oxide? If so, you should be able to do a separate molar balance on it. Look back to the original masses you posted: Those come pretty close to a 1:1:1 ratio for Zn, I2, and ZnI2.

rofgilead - I think your reaction would work well if it was an aqueous reaction. I'm sort of surprised that it's not, but apparently the Zn metal and I2 stay in solid form, despite the presence of the acetic acid.

And finally, I found this linky that seems pretty similar to what you're doing, jess.

pip - yeah, i think within the sig figs available here, those numbes are pretty accurate. considering that the amount of energy is in Joules, and if we look at an approximation like e=mc^2, m=e/c^2....that's going to be a *really* small mass that would gained or lost in bond rupture/formation.

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