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April 18, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Chemistry
carbon dioxide dissolves in water to form carbonic acid. Estimate the thermodynamic equilibrium constanst (K) for this reaction (delta Gf values: H2CO3= - 616.1, H2O= - 237.1, CO2= - 394.4) . Carbonic acid then ionizes in water (Ka1= 4.5 x 10^-7). Ignoring Ka2, estimate (K) ...
Friday, March 21, 2014 at 4:47pm

Chemistry-Repost for DrBob222
Well, it's this way. If you read the problem, as I did, the first line says you want to prepare 500 mL of a buffer. When I read that I quit reading and wrote instructions for preparing 500 mL of said buffer. You read the whole problem, which I should have done, and saw the...
Friday, March 21, 2014 at 4:24pm

Chemistry
Use the Henderson-Hasselbalch equation.
Friday, March 21, 2014 at 2:43pm

Chemistry-Repost for DrBob222
500 ml of a buffer solution with ph=2.10 must be prepared using .4 M HNO2 and solid KNO2. The ka value of HNO2 is 4e-3. a.) What mass of KNO2 should be added to 3 L of the HNO2 to make the buffer? b.) What is the buffer's pH after 150 ml of .5 M HNO3 is added? Your answer ...
Friday, March 21, 2014 at 2:34pm

Chemistry
I'm at a distinct disadvantage since I can't see the titration curve but I think this is what you do. The equivalence point is 7 (which I really don't understand since weak acids and strong bases are supposed to be somewhere in the 8.3 range for the eq pt but this ...
Friday, March 21, 2014 at 2:33pm

Chemistry-Repost for DrBob222
You can use the mg directly in the ratge equation. And I made a typo. That first line should have read, "Is that C60O3
Friday, March 21, 2014 at 2:22pm

Chemistry
Given that 20 ml of a weak acid (HA) was titrated with NaOH and the titration curve of pH vs titrant volume in ml is given, find the initial concentration of the acid? The problem gives the full titration curve starting at pH=2.2 at 0 ml added and with the equivalance pt at pH...
Friday, March 21, 2014 at 2:11pm

Chemistry-Repost for DrBob222
A sample of C60O3 decomposes with an activation energy of 50 kg/mol, an Arrehnius pre-factor of 2e10 s-1 and a k value of .04 s-1. How long does it take for a 25 mg sample at 25 degrees C to produce 10 mg. Your response was is that C60O<suh>3 or what? And I thought ...
Friday, March 21, 2014 at 2:06pm

Chemistry
.250L
Friday, March 21, 2014 at 1:28pm

Chemistry
What is the pH of a solution prepared by mixing 24.6 g sodium acetate and 50 mL of 2.5 M acetic acid in a 500 mL flask and filling to volume
Friday, March 21, 2014 at 12:58pm

Chemistry-Repost for DrBob222
Six of one but all roads lead to the same answer. You start with 0.01M NaOH and you dilute it from 50 to 100 which is a factor of 2. 0.01/2 = 0.005M OR 0.01M x (100/200) = 0.005 OR mols NaOH = M x L = 0.01M x 0.05L = 0.0005 mols and M = mols/L = 0.0005/0.1L = 0.005M (50 mL + ...
Friday, March 21, 2014 at 11:27am

Chemistry-Repost for DrBob222
You said you understood part a. That's the initial amount of MgF2 dissolved in the 1L of water. You should have done this for part a. ............MgF2 ==> Mg^2+ + 2F^- I...........solid.....0.......0 C...........solid.....x.......2x E...........solid.....x.......2x Ksp...
Friday, March 21, 2014 at 11:20am

Chemistry-Repost for DrBob222
The reaction OH- + NH4+ = H20 + NH3 is kinetically first order in both reactants' concentrations. The rate constant is 2e10 1/M s. If 50 ml of .01 M NaOH is mixed with 50 ml of .01 M NH4CL, find the time required for the OH- concentration to reach 1e-4 M. Your answer: It ...
Friday, March 21, 2014 at 10:39am

Chemistry-Repost for DrBob222
My question was: A saturated solution of MgF2 at 23 degrees C was prepared by dissolving solid MgF2 in 1 L water. The Ksp of MgF2 is 1.5e-5. a.)Calculate the mass of MgF2 dissolved. b.) When .1 mols of solid KF was dissolved in the MgF2 solution, precipitation was observed. ...
Friday, March 21, 2014 at 10:34am

Chemistry
dG = dH- TdS Set dG to zero and solve for T. That gives you the T for equilibrium, any move less than that moves in the non-spontaneous direction.
Friday, March 21, 2014 at 10:34am

Chemistry
Yes the compound is C(sub 60)O(sub 3). Sorry, the Arrenhnius stuff was to solve part a to find the k value and I understood that so I just added what I found for k. I thought you are supposed to use the equation, concentration of A equals initial concentration of A times e^(-...
Friday, March 21, 2014 at 10:12am

Chemistry?
If you had followed directions and put your SUBJECT in the School Subject box, you might have gotten an answer by now.
Friday, March 21, 2014 at 7:29am

Chemistry
The Heisenberg Uncertainty Principle: A student is examining a bacterium under the microscope. The E. coli bacterial cell has a mass of mm = 0.100fg\rm fg (where a femtogram, fg\rm fg, is 10−15g\rm 10^{-15}\; g) and is swimming at a velocity of vv = 7.00ìm/s\mu m/...
Friday, March 21, 2014 at 6:31am

Chemistry
The Heisenberg Uncertainty Principle: A student is examining a bacterium under the microscope. The E. coli bacterial cell has a mass of mm = 0.100fg\rm fg (where a femtogram, fg\rm fg, is 10−15g\rm 10^{-15}\; g) and is swimming at a velocity of vv = 7.00ìm/s\mu m/...
Friday, March 21, 2014 at 6:31am

Chemistry
The following reaction has the following standard thermodynamic parameters: Reaction: C(g) + D(g)----> E(g) Delta H rxn=-26.1kJ/mol and Delta S rxn=-69.8J/(mol*K). Calculate the temperature at which the reaction becomes nonspontaneous.
Friday, March 21, 2014 at 1:32am

chemistry
I don't think so. 1.6E-6/0.5 = ?
Friday, March 21, 2014 at 12:48am

Chemistry
I think what you have to understand is that on the flat portion, the temperature is constant because the phase change is occurring and the temperature cannot go up (if melting) or down(if crystallizing) until all of the molecules have melted or crystallized. At that exact ...
Friday, March 21, 2014 at 12:45am

Chemistry
See your other post. Worked the same way. Just take a 100 g sample.
Friday, March 21, 2014 at 12:38am

chemistry
Take a 100 g sample which gives you 75.2g N2 and 24.8g Kr. mols N2 = grams/molar mass mols Kr = grams/molar mass Then X = mol fraction XN2 = nH2/total mols XKr = nKr/total mols pN2 = XN2*total P pKr = XKr*total P
Friday, March 21, 2014 at 12:37am

Chemistry
Didn't I do this for you earlier?
Friday, March 21, 2014 at 12:31am

chemistry
2SO2 + O2 ==> 2SO3 mols SO2 = grams/molar mass mols O2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols SO2 to mols SO3 Do the same for mols O2 to mols SO3. It is likely these values will be different which means one of them is wrong. The...
Friday, March 21, 2014 at 12:22am

Chemistry
(amount recovered/amt you should recover)*100 = %yield
Friday, March 21, 2014 at 12:15am

General Chemistry
work = -p*delta V work = 7*0.52 = -3.64 L*atm Multiply by 101.325 if you want the answer in joules.
Friday, March 21, 2014 at 12:13am

chemistry
z
Thursday, March 20, 2014 at 11:43pm

Chemistry
okay so then Q = [5.69x10^-9]^2/1.3405 = 3.238x10^-9/1.3405 = 2.42x10^-9 ΔG = 42.20 + (.00833145)(298) ln (2.42x10^-9) = 42.40 + (2.477) (-19.84) = 42.40 + -49.144 = -6.74 rounded to 7 which is correct. Thank you sir! <3
Thursday, March 20, 2014 at 11:27pm

Chemistry
For the reaction A + B ==> C + D Q = (C)(D)/(A)(B) which looks like Keq but isn't. I suppose the simple answer is yes. You have two components of equal magnitude on the right and those are the products.
Thursday, March 20, 2014 at 10:48pm

Chemistry
I usually convert it (especially in ΔG = ΔGº + RTlnQ ) because it will confuse me other wise and I will get wrong numbers. I usually keep kJ because thats usually what I need, unless specified otherwise. I suppose I don't need to convert it for ΔG = ...
Thursday, March 20, 2014 at 10:43pm

chemistry
I don't know if that 1.85 atm is absolute or not; I assume this is to be worked the "easier" way. Use (p1/t1) = (p2/t2) Don't forget T must be in kelvin.
Thursday, March 20, 2014 at 10:40pm

Chemistry
Two comments. Shouldn't that Q be (5.69E-5)^2/(1.34)? Can you add dGo (in kJ) and RTlnQ (which I believe is in J) without convert one or the other?
Thursday, March 20, 2014 at 10:33pm

chemistry
The pressure in an automobile tire is 1.85 atm at 27.0°C. What will be the pressure if the temperature increases to 38.0°C?
Thursday, March 20, 2014 at 10:23pm

oops--CHEMISTRY
https://www.google.com/search?q=H+spectr​um+diagram&client=firefox-a&hs=DDB&rls=o​rg.mozilla:en-US:official&channel=sb&tbm​=isch&imgil=i479Ed5rU636WM%253A%253Bhttp​s%253A%252F%252Fencrypted-tbn1.gstatic.c​om%252Fimages%253Fq%253Dtbn%253AANd9GcS-&#...
Thursday, March 20, 2014 at 10:11pm

CHEMISTRY
Here is a diagram that should help answer this question.
Thursday, March 20, 2014 at 10:10pm

chemistry
If that's mols = grams/molar mass, yes.
Thursday, March 20, 2014 at 9:53pm

Chemistry
Is that C60O<suh>3 or what? And I thought Arrhenius equation had to do with k1 and k2 at T1 and T2 and T1 and T2 are tempeataures, not time.
Thursday, March 20, 2014 at 9:52pm

Chemistry
Approx means I've estimated. You should go through yourself and get good answers. pKa = approx 2.4 mols HNO2 = 0.5L x 0.4M = 0.2 = acid pH = pKa + log (base)/(acid) 2.10 = 2.40 + log (x/0.2) Solve for x = mols KNO2 = about 0.1 mol = ? grams. b. millimols HNO2 = 500 mL x 0....
Thursday, March 20, 2014 at 9:47pm

Chemistry HELP PLEASE!!
you're a life saver
Thursday, March 20, 2014 at 9:43pm

Chemistry HELP PLEASE!!
Mg^2+ + 2e ==> Mg(s) 2Cl^- ==> Cl2 + 2e Oxidation is the loss of electrons so which half rxn is that? Then oxidation occurs at the anode. Reduction occurs at the cathode (which is the gain of electrons).
Thursday, March 20, 2014 at 9:06pm

Chemistry
HClO(aq) + H2O (l) <> H3O+ (aq) + ClO-(aq) Calculate the value of ΔGrxn at 25 °C for hypochlorous acid when [ClO-]=[H3O+]=5.69x10^-5 M [HClO] = 1.340 M Previously calculated a ΔGºrxn of 42.20 kJ/mol Q = [5.69x10^-5] / [1.340] = .00004245 M equation ...
Thursday, March 20, 2014 at 9:05pm

chemistry
S is Positive
Thursday, March 20, 2014 at 8:31pm

Chemistry HELP PLEASE!!
write the oxidation and reduction half-reactions that occur at the anode and cathode, respectively, when MgCl2 liquid is electrolyzed using inert electrodes. HELP PLEASE!!!
Thursday, March 20, 2014 at 8:15pm

Chemistry
The mechanism for NH2NO2=N2O+H2O occurs in three steps: step 1: NH2NO2=NHNO2- + H+ (forward and reverse reactions are fast) step 2: NHNO2-=N2O+OH- (slow) step 3: H+ + OH-=H20 (very fast) What is the rate law for d[N2O]/dt as determined by the mechanism?
Thursday, March 20, 2014 at 6:33pm

Chemistry
500 ml of a buffer solution with ph=2.10 must be prepared using .4 M HNO2 and solid KNO2. The ka value of HNO2 is 4e-3. a.) What mass of KNO2 should be added to 3 L of the HNO2 to make the buffer? b.) What is the buffer's pH after 150 ml of .5 M HNO3 is added?
Thursday, March 20, 2014 at 6:06pm

Chemistry
A sample of C60O3 decomposes with an activation energy of 50 kg/mol, an Arrehnius pre-factor of 2e10 s-1 and a k value of .04 s-1. How long does it take for a 25 mg sample at 25 degrees C to produce 10 mg.
Thursday, March 20, 2014 at 6:03pm

chemistry
K=(pC^1*pD^3)/(pA^2*pB^2) then go deltaG=-RT*ln(K)
Thursday, March 20, 2014 at 5:32pm

CHEMistry
MOLES=MASS/MR
Thursday, March 20, 2014 at 5:21pm

chemistry
if you had 0.028 moles of copper sulfide, how many grams would you have?
Thursday, March 20, 2014 at 5:03pm

CHEMISTRY
I need to find the rate law of a reaction but ive only done so when factors cancel out, this one has all different numbers and im not quite sure what to do with it. It has time taken every second (which im assuming are the different trials) and different concentrations of OH...
Thursday, March 20, 2014 at 3:55pm

CHEMISTRY
CaCO3(s)+2HCl(aq)>CaCl2(aq)+H2O(l)+CO​2(g) I will estimate all of these numbers; you need to go through and recalculate each. mols CaCO3 = grams/molar mass = approx 0.30 mols HCl = grams/molar mass = approx 0.36 Convert mols CaCO3 to mols CaCl2 using the coefficients ...
Thursday, March 20, 2014 at 3:38pm

CHEMISTRY
An electron undergoes a transition from an n=3 to an n=1 stationary state and red light is released. Which of the following forms of electromagnetic radiation could be released for an n=2 to n=1 electron transition within the same atom? -blue visible light -yellow visible ...
Thursday, March 20, 2014 at 3:25pm

chemistry
Cabbage Juice Titration Lab connexus
Thursday, March 20, 2014 at 3:20pm

CHEMISTRY
CaCO3(s)+2HCl(aq)>CaCl2(aq)+H2O(l)+CO​2(g) how many grams of calcium chloride will be produced when 30 g of calcium carbonate are combined with 13 g of hydrochloric acid? Which reactant is in excess and how many grams of this reactant will remain after the reaction is...
Thursday, March 20, 2014 at 2:37pm

Organic Chemistry
Thanks anyway! I can ask one of my classmates to explain
Thursday, March 20, 2014 at 2:16pm

Chemistry needs help
Indicate your specific subject in the "School Subject" box, so those with expertise in the area will respond to the question.
Thursday, March 20, 2014 at 1:44pm

General Chemistry
A piston has an external pressure of 7.00 atm. How much work has been done in joules if the cylinder goes from a volume of 0.130 liters to 0.650 liters. Express your answer with the appropriate units.
Thursday, March 20, 2014 at 12:17pm

logic-math
Calculate the truth value (f or V) a. Is it true that if (the Papaya is a fruit from the Caricaseas or the Pitahaya is the fruit of a plat from the Cactaseas) then (el Cohombro is a fruit of a plant from the family of the Cucurbitaceas or the Nisper is a fruit of a tree from ...
Thursday, March 20, 2014 at 12:01pm

chemistry
Calculate the percent yield for an experiment in which 46.9 g of SO3 was produced upon the reaction of 51.2 g of SO2 with 25.0 g O2
Thursday, March 20, 2014 at 9:53am

Chemistry
If your Copper(II)sulfate solution contains 0.8 grams of Cu and you recovered 0.76 grams of it, what would be the percent yield?
Thursday, March 20, 2014 at 9:38am

Chemistry
The Ksp of tin(II) hydroxide, Sn(OH)2, is 5.45 × 10-27. Calculate the solubility of this compound in g/L.
Thursday, March 20, 2014 at 1:09am

Chemistry
Ok, makes sense. Thanks!
Thursday, March 20, 2014 at 12:45am

chemistry
A gas mixture contains 75.2% nitrogen and 24.8% krypton by mass. What is the partial pressure of krypton in the mixture if the total pressure is 853mmHg ?
Thursday, March 20, 2014 at 12:20am

Chemistry
A heliox deep-sea diving mixture contains 2.0 g of oxygen to every 98.0 g of helium.What is the partial pressure of oxygen when this mixture is delivered at a total pressure of 8.9atm ?
Thursday, March 20, 2014 at 12:16am

chemistry
Did you try doing the Stoichiometric equation? Mg - 24.31 g Cl - 35.45 g Total Mass - 59.76 g 29g MgCl (1 mol MgCl/59.76g)= the answer.
Thursday, March 20, 2014 at 12:15am

Chemistry
They're back together in their new state. ICE (Slant)<-- Crystalloid formed molecules; they are vibrating slightly but packed together so tightly they do not move. As TRANSITION FROM ICE TO LIQUID <-- since heat is being applied molecules are moving about more and ...
Thursday, March 20, 2014 at 12:04am

Chemistry
If I could draw a diagram but I can't. Let me try to use periods as spaces. E = k/N2 .....1.....2.....3.....4.....inf E = -21...-9....-4....-3......0 In going from n = 1 to n = 2 we have dE = 13 Going from 1 to 3 we have dE = 17 Going from 1 to 4 we have dE = 18 Going form...
Wednesday, March 19, 2014 at 11:55pm

Chemistry
In a heating and cooling curve, I understand that the flat part means that the bonds are either forming or breaking, depending on if the input of energy is increasing or decreasing, but what is happening to the bonds in the slanted parts? Thanks!
Wednesday, March 19, 2014 at 11:29pm

chemistry
How many moles of sodium chloride can be produced if 29g of Magnesium Chloride are reacted in the reaction 2NaNO3 + MgCl> 2NaCl+Mg (NO3)2?
Wednesday, March 19, 2014 at 10:46pm

Chemistry
The energies, E, for the first few states of an unknown element are shown here in arbitrary units: n= 1, E=-21 n=2, E=-9 n=3, E=-4 n=4, E=-3 ...,... infinity, 0 A gaseous sample of this element is bombarded by photons of various energies (in these same units). Match each ...
Wednesday, March 19, 2014 at 10:33pm

chemistry
*the molar solubility of BaCo3 in 0.50M Bacl2 solution IS?ksp(1.6*10^-6) I CALCULATED AND GOT 3.2*10^-9 WANT TO MAKE SURE IF IT CORRECT
Wednesday, March 19, 2014 at 10:24pm

Chemistry [back-titration] - please check my sol'n
I get it now. I didn't think about the reaction of Fe^2 and Cr2O7^2-. I thought they would produce FeCr2O7, so I thought they're in 1:1 ratio. Yes, I got 159.6 g/mol as weight of TeO2 (as what I've typed above). :) Yes, I've seen the post about the nuclear chem...
Wednesday, March 19, 2014 at 10:24pm

chemistry
a certain riffle bullet has a mass of 6.45 g. calculate the de broglie wavelength of the bullet traveling at 1817 miles per hour.
Wednesday, March 19, 2014 at 10:18pm

Chemistry
1. A chemist prepares a solution by dissolving 4.603 g of NaNO3 in enough water to make 200 mL of solution. What molar concentration of sodium nitrate should appear on the label? Answer in units of M 2.If the chemist mistakenly makes 225 mL of solution instead of the 200 mL, ...
Wednesday, March 19, 2014 at 9:57pm

CHEMISTRY
What is the mass in grams of one Mole of water?
Wednesday, March 19, 2014 at 9:54pm

Chemistry
I believe it's 2.992x10^-23 grams... not sure
Wednesday, March 19, 2014 at 9:53pm

Chemistry
If 689000 J of energy are added to 4.00 L of water at 284 K, what will the final temperature of the water be? Answer in units of K
Wednesday, March 19, 2014 at 9:50pm

Chemistry
Determine the specific heat of a material if a 34.7 g sample absorbed 45.2 J as it was heated from 293 K to 318 K. Answer in units of J/g · K Your answer must be within ± 2.0%
Wednesday, March 19, 2014 at 9:48pm

Chemistry
what is the mass in grams of one molecule of water?
Wednesday, March 19, 2014 at 9:40pm

Chemistry
I'm sorry but I am still so confused on pretty much everything. How do you calculate the new solubility? And how do you convert that to g MgF2 in 1L? And what is the initial amount that you subtract from?
Wednesday, March 19, 2014 at 9:33pm

chemistry
YOU CAN USE ALGEBRA! energy absorbed=given grams x specific heat x (unknown final temperature-initial temp) SO: 255=4.90(.129)(x-24) 255=0.6321(x-24) DIVIDE BOTH SIDES BY .6321 .6321(255)=(.6321(x-24))/,6321 403.42 = x-24 +24 +24 ---------------- x=427.42
Wednesday, March 19, 2014 at 9:28pm

Chemistry
How do you find the initial concentration of the acid give the titration curve of a weak acid-strong base titration?
Wednesday, March 19, 2014 at 9:22pm

Chemistry
Calculate the pH of the solution that results from mixing 30.0 mL of 0.050 M HCN(aq) with 70.0 mL of 0.030 M NaCN.
Wednesday, March 19, 2014 at 9:20pm

AP Chemistry
Thank You. This question totally broke me
Wednesday, March 19, 2014 at 9:03pm

AP Chemistry
I think Ag comes out first followed by H2, then Fe if ever.
Wednesday, March 19, 2014 at 8:57pm

Chemistry
Why do you divide .01 by 2. Shouldn't you divide by 1 because 50 ml+50ml=1L
Wednesday, March 19, 2014 at 8:52pm

Chemistry
4
Wednesday, March 19, 2014 at 8:45pm

chemistry
Johnny said he didn't have a calculator and wants someone to do his work. I did one problem. Then Danny says his calculator returns the wrong answer so it may be broke(n). Then I find Danny and Johnny are the same computer. :-(. Do we have an answer moocher?
Wednesday, March 19, 2014 at 8:20pm

AP Chemistry
A solution is 1.0M in AgNO3 and Fe(NO3)2.in the electrolysis of this solution using inert electrodes, the voltage is gradually increased. What is the order in which the substances in the solution would plate our or react at the cathode ? Assume that the overvoltage of hydrogen...
Wednesday, March 19, 2014 at 8:09pm

Chemistry
Use the Henderson-Hasselbalch equation.
Wednesday, March 19, 2014 at 7:57pm

Chemistry
The b part is a common ion problem; i.e., F^- is the ion common to both KF and MgF2. For part b, Ksp = (Mg^2+)(F^-)^2 The common ion shifts the solubility to the left. MgF2 ==> Mg^2+ + 2F^- because of Le Chatlier's Principle. The new solubility will = new (Mg^2+) and ...
Wednesday, March 19, 2014 at 7:57pm

Chemistry
If your equation is right use 2 mol e. However, I'm somewhat surprised In doesn't go to In^3+.
Wednesday, March 19, 2014 at 7:41pm

Organic Chemistry
Lauren, I'm sorry but we can't draw structures on this forum. You might try Google but that sounds so specific I don't know how much luck you will have.
Wednesday, March 19, 2014 at 7:35pm

CHEMISTRY
I need to find the rate law of a reaction but ive only done so when factors cancel out, this one has all different numbers and im not quite sure what to do with it. It has time taken every second (which im assuming are the different trials) and different concentrations of OH...
Wednesday, March 19, 2014 at 7:25pm

Chemistry
It starts at 0.01/2 = 0.005 and you want it to go to 1E-4 ln(5E-3/1E-4) = 2E10*t Solve for t.
Wednesday, March 19, 2014 at 6:52pm

Organic Chemistry
Draw every stereoisomer for 1-bromo-2-chloro-1,2-difluorocyclopentan​e. Use wedge-and-dash bonds for the substituent groups, and be sure that they are drawn on the outside of the ring, adjacent to each other.
Wednesday, March 19, 2014 at 6:44pm

Chemistry
Calculate the change in mass of the In electrode after the cell supplies 100 mA of current for 10 minutes. The balanced redox reaction is 2In+Cl2=2In+ + 2Cl-. I understand the idea behind the question, I just don't know if I should use 1 mol In per 1 mol e- or 1 mol In per...
Wednesday, March 19, 2014 at 6:27pm

Chemistry
The reaction OH- + NH4+ = H20 + NH3 is kinetically first order in both reactants' concentrations. The rate constant is 2e10 1/M s. If 50 ml of .01 M NaOH is mixed with 50 ml of .01 M NH4CL, find the time required for the OH- concentration to reach 1e-4 M.
Wednesday, March 19, 2014 at 6:04pm

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