<p>Do I have to know this for the SAT Chem test? Each of the Barron's practice tests has had one question pertaining to the ion-electron method, but it's sooooo annoying....</p>
<p>i havent taken the actual sat chem yet, but i would doubt it. from the practice tests ive taken (sparknotes), you just have to be able to balance redox any way you have to.</p>
<p>how long were the reactions? This one had like 3 species on each side. Horrible.</p>
<p>just a short reaction of 1 or 2 species per side is the worst i’ve seen (so far). mind posting the equation, just so i can try it out? :D</p>
<p>Yes there are a few of those on the real test, but they’re not impossibly hard. You most likely won’t get anything where the coefficients start to enter the double digits.</p>
<p>Familiarize yourself with acid and basic half reaction balancing as well, and it’ll be a breeze.</p>
<p>@123Testing This is #35 Test 1 from the Barrons book
KMnO4 + H2SO4 -----> K2SO4 + MnSO4 + H2SO4 +H2O
(potassium permanganate +sulfuric acid -----> potassium sulfate +manganese sulfate +sulfuric acid +water)</p>
<p>It asked what the correct reduction half-reaction for the balanced equation was. The choices were actually really easy, since only one was a reduction equation, but I was so bewildered it just blew over my head. </p>
<p>
Mind posting an example too? :)</p>
<p>Sure.</p>
<p>Take for instance, the half reaction Cr2O7 2- ==> Cr 3+, which takes place in acidic reactions. You won’t need to know how to derive the complete half reaction (that’s more of an AP chemistry area), but you should be able to recognize whether they’re acidic or basic, oxidizing or reducing, and how many moles of electrons are present.</p>
<p>You should also be able to balance the reactions when given all of the reactants and products, but need to fill in the coefficients. Remember to take into account the charges on each side. They must be equal (But not necessarily 0).</p>
<p>Fully balanced half reaction above is 6e(-) + 14H(+) + Cr2O7(2-) ==> 2Cr(3+) + 7H20.
It is acidic, being reduced, and there are 6 moles of electrons.</p>
<p>^Thank you so much for explaining that! So I’m going to guess that in basic reactions, the species gets oxidized (loses electrons).</p>
<p>w00t.</p>
<p>@hungryjoe: i have never heard of the acidic and basic half reactions before…i probably shouldn’t worry myself over it though :P</p>