<p>Balance: Cu2+ + I- --> CuI + I2</p>
<p>Why wouldn't the coefficient of I- be 3?</p>
<p>it would be 2... 2 electrons are transfered from cu 2+ so 2 must be from I-</p>
<p>it's a redox reaction (disproportionation, err however you spell it) so gyros is right and the the electrons transferred has to be equal as well as each element.</p>