<p>I got 62.4% for the percent mass question as well.</p>
<p>For accounting for the fact that N2H4 is basic in water I said this happens:</p>
<p>N2H4+2H2O->2NH3 + 2OH-.</p>
<p>1
a pH=1
b
i)
ii)
c
i)
ii)
d
i) No
ii) .00667</p>
<p>2
a
i)
ii)
iii)
iv) NahCO3
b 0.00376moles
c 62.4 %</p>
<p>3</p>
<p>a -571.6KJ
b -1417 KJ
c
d 2H2 + O2 2H2O
e 1.23
f
i) 1.86
ii) 300
gFuel cells based on butane release Carbon Dioxide gas which is detrimental to the Earth, potentially aggravate global warming, etc. Also, butane cells require the use of Butane, which is a highly flammable, combustible hydrocarbon. It can thus be dangerous to use, etc. Hydrogen cell simply gives off water and is much safer and environmentally friendly. </p>
<p>4
a
i)
ii) 100 mL
b
i) Cu + 2Ag+ –> Cu2+ + Ag
ii) Cl
c
i)
ii) Silver flakes start to attach to copper wire</p>
<p>5
a
b No
c
d
e Red-Ox
f Positive
g False</p>
<p>6
a Equal
bAverage kinetic energy of molecules, and therefore average speed of the gas molecules, is directly related to absolute temperature. When you increase temperature, you are increasing average kinetic energy and average speed. More gas molecules are moving at faster speeds in random chaotic motion and their collisions are elastic. The total force in the container thus increases while the area is the same. Thus, the pressure increases.
c
i) Zero
ii) Rate = k
iii) .0000040 M/sec = k
d .8 atm</p>
<p>for 4cii) does the copper becoming ions change the color of the solution?</p>
<p>@enfield, that’s the exact equation I put for the N2H4 question, but most people told me it was N2H4 + H2O –> N2H5+ + OH-.</p>
<p>Then again, the question says “write A balanced equation”, so do you think they’d accept the ammonia one o.O?</p>
<p>Edit: @tomato, I put that the solution turns blueish greenish because of copper ion, too xD.</p>
<p>^^ some people said yes.
I wrote it, so I"m hoping it’s right.</p>
<p>^ I hope they accept ammonia!</p>
<p>Please please please add some of your answers to the list, I want to have it filled out so I can compare my answers (esp for #1)</p>
<p>for 4ai) i put Mg(OH)(2) + 2H+ ----> 2H(2)O + Mg2+</p>
<p>When adding a strong acid to a weak base, you create a buffer solution.</p>
<p>[Titration</a> of a Weak Acid with a Strong Base](<a href=“http://www.chem.ufl.edu/~itl/2045/lectures/lec_z2.html]Titration”>http://www.chem.ufl.edu/~itl/2045/lectures/lec_z2.html)</p>
<p>For 1bii, I got 1.34E-3 moles/liter = [OH-].
And for 1cii, I put 9.26 = pH.
Anyone else, too?</p>
<p>@tomato: That’s what I got xD!</p>
<p>5c) Both N(2)H(4) and C(2)H(6) have dispersion forces, but N(2)H(6) also exhibits hydrogen bonding. This means that it takes more energy to change the phase of a N(2)H(6) molecule than a C(2)H(6) molecule, thus resulting in a higher boiling point for hydrazine.</p>
<p>i got 9.26 pH using henderson, yep!</p>
<p>@kikuhana, i got pH of 9.26 too :)</p>
<p>I got like, 6.2.
):</p>
<p>did anyone get the last part of the first question right? the one where they ended up mixing all three together? that totally stumped me, lol.</p>
<p>what did you guys get for 2ai) ?</p>
<p>@echoyjeff222, it stumped me too, cii) thru d) for #1 was hard for me</p>
<p>Here’s what I got for b and c of FRQ1… is this what most others got…?</p>
<p>bi. Kb = ([NH4+][OH-])/[NH3]</p>
<p>ii. NH3+ H2O ==> NH4+ + OH-
I .100M - 0 0
C -x - +x +x
E .100-x - x x</p>
<p>Kb =1.8x10^-5 = x^2/(.100-x) (Assume x is negligible if subtracted)</p>
<p>[OH-] = x = .00134M</p>
<p>ci. Ka*Kb = 1.0x10^-14
Ka= (10^-14)/(1.8x10^-5) = 5.6x10^-10</p>
<p>ii. pOH = pKb + log([NH4+]/[NH3])
mixing beakers two and three will result in equal concentrations of NH4+ and NH3, therefore:
pOH = pKb = -log[1.8x10^-5] =4.7
pOH + pH = 14
pH= 14-4.7 = 9.3</p>
<p>1
a pH=1
b
i) 5.55 E -10
ii) 1.34E-3 moles/liter = [OH-].
c
i)
ii) 9.26
d
i) No
ii) .00667</p>
<p>2
a
i)
ii)
iii)
iv) NahCO3
b 0.00376moles
c 62.4 %</p>
<p>3</p>
<p>a -571.6KJ
b -1417 KJ
c
d 2H2 + O2 2H2O
e 1.23
f
i) 1.86
ii) 300
gFuel cells based on butane release Carbon Dioxide gas which is detrimental to the Earth, potentially aggravate global warming, etc. Also, butane cells require the use of Butane, which is a highly flammable, combustible hydrocarbon. It can thus be dangerous to use, etc. Hydrogen cell simply gives off water and is much safer and environmentally friendly. </p>
<p>4
a
i) Mg(OH)(2) + 2H+ ----> 2H(2)O + Mg2+
ii) 100 mL
b
i) Cu + 2Ag+ –> Cu2+ + Ag
ii) Cl
c
i)
ii) Silver flakes start to attach to copper wire</p>
<p>5
a
b No
cBoth N(2)H(4) and C(2)H(6) have dispersion forces, but N(2)H(6) also exhibits hydrogen bonding. This means that it takes more energy to change the phase of a N(2)H(6) molecule than a C(2)H(6) molecule, thus resulting in a higher boiling point for hydrazine
d
e Red-Ox
f Positive
g False</p>
<p>6
a Equal
bAverage kinetic energy of molecules, and therefore average speed of the gas molecules, is directly related to absolute temperature. When you increase temperature, you are increasing average kinetic energy and average speed. More gas molecules are moving at faster speeds in random chaotic motion and their collisions are elastic. The total force in the container thus increases while the area is the same. Thus, the pressure increases.
c
i) Zero
ii) Rate = k
iii) .0000040 M/sec = k
d .8 atm</p>
<p>so is 6c iii) positive or negative 4x10^-6…?
because as I look through the kinetics chapter of princeton review, whenever they list the rate of disappearance of reactants, its always a positive value. and since rate = k for a zero order reaction, k would be positive. and i’m pretty sure my teacher gave us a chart that said the slope of a zero order reaction is equal to -k, which doesn’t necessarily mean that k is negative just that the slope is.
oh well, just 1 point</p>
<p>Walle, I’m pretty sure it’s positive, as you cannot have negative molarity.</p>
<p>I put the rate as negative 4.0 x 10^-6.
Maybe they’ll let us have the point since putting the negative sign indicates that we know it’s the rate of <em>disappearance</em>. Or… I dunno x_x.</p>