<p>also about the separation method the 5th answer was sublimation which I put and I am wrong. you are right with distillation.</p>
<p>I am also wrong about PO4 - it is basic.</p>
<p>Doesn't joining atoms to form a compound (H2 + O2) require energy, thus making it endothermic? Whereas breaking bonds releases energy (exothermic)?</p>
<p>NH4+ by itself (forget OH- for a sec) is a stronger acid than H2O => H2O would be preferred as a product. Moreover OH- is a much stronger base than NH3 => the weaker NH3 would be preferred as a product.</p>
<p>NH4OH is not a base. NH4+ is and acid, OH- is a base. NH3 is a base too.</p>
<p>requires energy only to overcome barrier. requiring energy does not mean a reaction is endothermic - you have to know whether after energy is taken in how much is given offf - net give off means exo, net take in - endo. it's exo. i looked it up.
It goes like this: energy is needed to weaken the bonds of H-H and ::O=O::. Then H-O-H is formed and it is definitely less stable hence of higher energy than H2 and O2 because the bonds of the latter are strong. When a product is less stable than reactants NET energy is given off after you account for the activation energy.
Remember the curve goes up bec you almost always need energy. When the peak is not too big - it means that the energy is taken from the surroundings easily under normal conditions. When the peak is big you have to put it in - heat, electrictiy, UV because the energy around is not enough. In the end however the size of the peak doesnt matter. You look at the end of the curve and the beginning of the curve and the difference tells you if it is exo or endo.</p>
<p>Martinibluex, dissolving Na3PO4 salt does produce a basic solution because it is the hydrolysis of an strong basic ion (Na+) and weak acidic ion (PO4(3-)):</p>
<p>Na3PO4(s) + H2O ----> Na+(aq) + OH(aq) + HPO42(aq)</p>
<p>Check out <a href="http://mailer.uwf.edu/listserv/wa.exe?A2=ind9801&L=chemed-l&D=1&F=&S=&P=562%5B/url%5D">http://mailer.uwf.edu/listserv/wa.exe?A2=ind9801&L=chemed-l&D=1&F=&S=&P=562</a></p>
<p>And I think H2O molecules do have stronger bonds than H2 and O2 because the reaction to form water is highly EXOTHERMIC, so water is more stable than either reactant. As for the lost of H+ by water molecule, this has more to do with solution ionization than the bonds themselves - at least that's how I reasoned the question out.</p>
<p>Goldshadow, making water from hydrogen and oxygen is exothermic because the heat/energy given off by the production of water is more than the heat required for the activation energy. Plus, electrolysis, which is used to break down water into its gaseous components, is endothermic because it requires energy/electricity. So the reverse reaction, which is the synthesis of water, is exothermic.</p>
<p>I corrected myself about the PO4. It does. You are right. Not the water though.</p>
<p>The Direction of an Equilibrium:</p>
<pre><code> The size of the equilibrium constant indicates which side of a reaction is favored at equilibrium.
NH3(aq) + H2O = NH4+(aq) + OH-(aq)
Kc = 1.8?10-5
Equilibrium lies to left
</code></pre>
<p>Ok I am checking the water thing now....
and here is my new argument. H2O has bonds that are very polar. H2 and O2 are non-polar and are therefore stronger. </p>
<p>Ionization is breaking of of polar covalent bonds.</p>
<p>Bonds in O2 are 499. H-O are 460.
In total if you sum up the energies the ones on the left are higher. However, the bonds in H2O are not weaker than the bonds in O2.</p>
<p>"If we replace weak bonds with strong bonds or more bonds
Then the formation is EXOTHERMIC and gives off heat."
Left side 3 bonds. Right side 4 bonds.</p>
<p>Oh yeah, what about the question that involved chemistry? Did anybody get that one?</p>
<p>I think that many people missed it.</p>
<p>What was the bunsen flame question?</p>
<p>Yes, Na3PO4 + H2O is basic. That wasn't the question. But does that imply that HPO4 -3 accepts the proton and turns into HPO4 -2 and OH-? </p>
<p>For the H2 + O2 => H2O thing... I'm pretty sure there was a question about exothermic reactions in barrons saying that in an exothermic reaction, the product is more stable than the reactants.</p>
<p>I put that there was too much oxygen for the bunsen flame question, because if you open the air valves, the flame turns blue</p>
<p>And for the I, II, III type of question that asked about reaction rate what did you guys put? The three choices (I think) were:
Rate = k[X][Y]^2
I. doubling the concentration of x will double rate
II. doubling the concentration of y will double rate
III. for every mole of x used, two moles of y are used</p>
<p>I put just I. II is definetely wrong, as doubling Y will quadruple rate. I wasn't sure about III though. I thought the exponents had nothing to do with the coefficients of the reaction.</p>
<p>I just found out on a chemistry site (<a href="http://www.chem.tamu.edu/class/majors/tutorialnotefiles/intra.htm%5B/url%5D">http://www.chem.tamu.edu/class/majors/tutorialnotefiles/intra.htm</a>) that the "larger the difference in the electronegativities of the atoms in a bond, the stronger the strength of the bond," so that means O-H bonds in water are stronger than the nonpolar bonds in O2 and H2. But also, in the T/T/CE question:</p>
<p>Bonds in NH3 are stronger than bonds in PH3
because
N is more electronegative than P</p>
<p>it is F/T - argh! I put T/T/CE</p>
<p>Sry, correction, it was "Bonds in NH3 are weaker than bonds in PH3"</p>
<p>The bonds in NH3 are stronger than the ones in PH3. I got that one wrong.</p>
<p>The fact that the making of H2O is exothermic simply means that the sum of the bond energies on the right is bigger than thge sum of the bond energies on the left. However, here moles and numbers of reactants and products also come into place. If you have if you have more bonds or more molecules on the right, it could be true that SOME bonds will be weaker than some bonds on the right.
It is a fact that the bond in 02 is stronger than the H-O bond in H2O if nothing else SIMPLY BECAUSE IT'S A FRELLING DOUBLE BOND :D
To summarize 1. exoth 2. F</p>
<p>Dekans 6: Doublebond in O2 man. Double.</p>
<p>::O=O::</p>
<p>O=O is stronger than H-O.
It says so in every table I looked.
Case closed.</p>
<hr>
<p>Dekans 6: Also PO4 3- is basic but Na+ is not a basic ion do not embarrass yourself. Na+ will NEVER take an H+ from anybody. It is extremely weakly acidic and only in reactions like NaH + CH3CH2Li -> Na+ + CH3CH3 + Li+ it shows that acidic character.
Then a HYDRIDE ION IS LOST (H-) which can only happen when really really strong bases take it:
Examples for 2 of the strongest bases ever that can do it: CH3CH2Li (in tables put as CH3CH2-) and NaNH2 (in tables put as NH2- / the minus is actually on N/)</p>
<p>Dekans 6 or anybody:
Now I know that reaction with the Na3PO4+H2O very well. However, the equilibrium lies to the left simply because the left side contains the weaker base and weaker acid and we all know that. </p>
<p>So yes, I do think that PO4 3- has a basic character in a sense that it might tale the H+ of some molecules BUT not water. No man.
Deprotonating water could be done by: NH2-, CH3CH2-, CH3CH2O-, Na in a radical reaction, NaH and also I think a ketone that has lost its alpha H.
Trust me, PO4 3- CAN NEVER TAKE THE "H" OFF OF WATER. HO- is simply too strong of a base to allow that. Only stronger bases than OH- can take the H of H2O to give OH-.
Any table of ionization constants of acids and their conjugate bases is going to tell you that HO- is a strongerbase than PO4 3-.</p>
<p>I am a premed in college with a 4.00 taking intermediate O-chem and getting an A in it. I took the SAT II only to try and transfer to MIT. However, I did make some mistakes because I didn't do ANY preparation and it has been awhile since I took general chemistry. But when I am sure about something you better check your sources.</p>
<p>By "basic ion" I meant salt of a strong base</p>