<p>
</p>
<p>No that’s what I am asking about, it should be in equilibrium, but the answer is not</p>
<p>@sporty04: So let’s say you have 30 balls in a 3 kg of bath water. If you take 1/3 of everything in the tub out, you’ll be left with around 20 balls and 2/3 of the bathwater. The ratio is still the same (30:3 = 10, 20: (2/3) = 10), despite the volume change. </p>
<p>Now you can think of the balls as the solute ions and the bath water and balls combined as the solution. The ratio of balls to bath water can be considered molarity :D</p>
<p>here are some short frq practice. just write the reaction. no need to balance:</p>
<p>a) Sodium metal is added to water
b) Dilute sulfuric acid is added to a solution of lithium hydrogen carbonate
c) Ethanl and formic acid (methanoic acid) mixed and warmed
d) Excess concentrated potassium hydroxide solution added to a precipitate of zinc hydroxide
e) Boron trifluoride gas mixed with ammonia gas</p>
<p>Just a random questions for all of you 5 hopefuls: What do I need to know for electrochem? We never went over the chapter in class and right now, all I’m trying to do is learn how to use the equations on the given sheet. Anything else I need to know? Some key facts? Thanks!</p>
<p>■■■ i suck at electrochemistry:</p>
<p>guys how do you know when something is the cathode and when something is the anode? if they just give u a drawing with Ni(NO3)2 on one side, Zn(NO3)2 on the other HOW DO YOU KNOW WHICH IS THE ANODE? ■■■■■</p>
<p>wat do you do in general? thanks!</p>
<ol>
<li><p>0.002 M KOH * (1 L/1000 mL) * (10mL) = 2 x 10^-5 mol KOH
2 x 10^-5 mol KOH/0.020 L = 1 x 10^-3 M KOH
pH is 11. :D</p></li>
<li><p>NH4Cl (aq) and HCl (aq)
Since their both acids, they don’t release gas, change colors, emit light, or change in temperature, meaning that no reaction is observed.</p></li>
<li><p>193,000 seconds.</p></li>
</ol>
<p>Ni+2 + 2e- -> Ni</p>
<p>2 (moles of electrons) = q (charge in coloumbs)/96,500 (Faraday’s constant)
q = 193,000</p>
<p>1 (current) = 193,000 (charge)/x (time)
x = 193,000</p>
<p>just remember an ox red cat
anode is oxidization
cathode is reduction</p>
<p>Other stuff: a high reduction potential (positive, large magnitude) means that a substance i likely to be reduced and it is a strong oxidizing agent, and a high oxidation potential means that it is likely to be oxidized and it is a strong reducing agent</p>
<p>@miheonigirisan: RED CAT, AN OX</p>
<p>REDuction CAThode
ANode OXidation</p>
<p>@th3lolz: Ahh, you beat me to it :P</p>
<p>hey guys, i’ll be taking AP chem tomorrow too!
just wanted to wish everyone luck before i do last minute review :)</p>
<p>you need to look at your table of standard reduction potentials. Remember that delta(g)=-nFE, and a spontaneous reaction will occur if delta G is negative, meaning that the cell potential is positive. The more positive a reduction potential, the more likely it will occur. In your example, Nickel’s reduction potential is -.25 and zinc’s is -.76. Therefore, Nickel will be reduced and Zinc will be oxidized. The E(cell) will be -.25-(-.76)=.51. Therefore, the reaction will be spontaneous. btw to calculate E(cell), just remember that the cathode is reduced and the anode is oxidized, then use cathode-anode, which is what i did above.</p>
<p>usually they give you the reaction.
for example, take this reaction:
2Ag+ + Cu(s) –> 2Ag(s) + Cu2+</p>
<p>the half-reaction that is going forward is Ag+ + e- –> Ag(s)
this means that it is being reduced. whatever is being reduced is at the cathode.</p>
<p>therefore, the Cu(s) –> 2e- + Cu2+ is the reverse of its reduction, so it is being oxidized, and oxidation happens at the anode.</p>
<p>
</p>
<p>You need reduction potentials, but the one thats reducing is the cathode and the one thats oxidizing is the anode.</p>
<p>So…
Ni2+ + 2e- —> Ni -0.25V
Zn2+ + 2e- —> Zn -0.76V</p>
<p>The total V must be positive (assuming spontaneous reaction)
To get a positive number, Zn must be oxidizing (-0.76V –> +.076V and -0.25V+.076V=.51V)
So your Zn is at the anode and your Ni is that the cathode</p>
<p>Correct me if I’m wrong PLEASE</p>
<p>lol if anything kills me, its gonna be the reaction part of the free response</p>
<p>does anybody know of any good practice besides the ones posted on the collegeboard site (the free responses of the last few years)</p>
<p>@th3lolz</p>
<p>heres some practice;</p>
<p>a) Sodium metal is added to water</p>
<p>b) Dilute sulfuric acid is added to a solution of lithium hydrogen carbonate</p>
<p>c) Ethanl and formic acid (methanoic acid) mixed and warmed</p>
<p>d) Excess concentrated potassium hydroxide solution added to a precipitate of zinc hydroxide</p>
<p>e) Boron trifluoride gas mixed with ammonia gas</p>
<p>[AP</a> review & temporary](<a href=“http://griffithchem.com/Chem%20AP2.html]AP”>http://griffithchem.com/Chem%20AP2.html)
Here’s a good review site to look at…</p>
<p>Wow, those are pretty hard.</p>
<p>A.) Na + 2H2O -> Na+ + 2OH- + H2
B.) SO4 -2 + 2LiHCO3 -> Li2SO4 + 2HCO3-
C.) C2H5OH + HCOOH -> H2O + C2H5COOH
D.) KOH + ZnOH -> K+ + Zn+2 + 2OH-
E.) BF3 + NH3 -> H3BNF3</p>
<p>Meh I’m gonna do these… I know they will be all wrong lol</p>
<p>a) Na + H2O -> Na+ + OH- + H+</p>
<p>b) 2H+ + SO42- + LiHCO3 -> LiHSO4 + H2CO3 (aka H2O + CO2) HAHA SUCH A FAIL</p>
<p>c) C2H5OH + HCOOH -> ESTER? so H2O + C2H5COOH that’s not an ester but it has the right molecular formula… can i just write C3H6O2 to be safe? >.< </p>
<p>d) 2K+ + 2OH- + Zn(OH)2? -> lol idk at all gonna guess 2K(OH) + Zn2+ + 2OH-</p>
<p>e) I KNOW THIS ONE YAY ITS A COMPLEX, si? lewis acids and bases are yummy
BF3 + NH3 -> (BF3)(NH3) probs wrong notation lol</p>
<p>EDIT: HAHA large fail. tmanneopen, make sure you separate things into ions at the beginning (KOH is K+ +OH-) not that i should be talking about doing this wrong</p>
<p>EDIT2: @ATastyBurger, not sure if that was at me but I started with “I know they will be all wrong lol” :P</p>
<p>^ your d looks wrong. Wouldn’t it be 2OH- + ZnOH2 -> Zn(OH)4 2+?</p>
<p>thanks guys</p>
<p>also in a phase diagram, if the line dividing solid and liquid has a positive slope, it means the solid is more dense right?</p>
<p>@the3lolz, yes… if you see a negative slope chances are it’s water since ice is less dense than liquid water</p>