Friday
April 24, 2015

Posts by DrBob222


Total # Posts: 48,504

chemistry
Not quite. Thanks for showing your work. 0.00150/40 = mols KOH and that's right. But that's divided by L (0.500) and not 500. That give you about 7.4E-5 and that is the (KOH) in the solution. Take the -log of that to give pOH and subtract from 14 to obtain the pH.
March 21, 2015

chemistry
DON'T USE all lower case for chemical symbols. CO is carbon monoxide. Co is cobalt. co is the abbreviation for company. It doesn't tell us a thing. And I don't like Fe2 either. I assume you were in such a hurry you omitted the rest of the formula of Fe2O3. Finally...
March 21, 2015

chemistry
Why are you posting this again. I thought we took care of this below. Your 4.47 was/is correct.
March 21, 2015

Chemistry 2
You really need to find the arrow key and use it. .....2HI ==> H2 + I2 I.................... C.................... E......y......x....0.351 So if I2 is 0.351 that means H2 is 0.351 (and that does NOT means HI is 0.351). Write the Kc expression, substitute for H2 and I2 and ...
March 21, 2015

chemistry
HCl + KOH ==> KCl + H2O mols HCl = M x L = 0.015 mols KOH = the same since 1 mol HCl reacts with 1 mol KOH = 0.015 Then M KOH = mols KOH/ L KOH. You know M and mols, solve for L. 1.00 = 0.015/L and L = 0.015/1.00 = 0.015L. Convert that to mL for 15 mL.
March 21, 2015

chemistry
To add a little clarification to the answer already posted. The correct answer to 3 s.f. is 100. and the period at the end is necessary and it not the end of the sentence. That sometimes leads to confusion and another way to do it to write 1.00E2 and that way a period is not ...
March 21, 2015

chemistry
Steve is right. CCl3COOH is not it.
March 21, 2015

Analytical Chemistry
I assume the half cell for the Pt/O2 couple is 4H^+ + 4e + O2 ==> 2H2O E = 1.229 v as a reduction. Add that to the H2 couple of H2 ==> 2H^+ + 2e E = 0 as an oxidation. The cell reaction then is 2H2 + 4H^+ + 4e + O2 ==> 2H2O + 4H^+ 4e The 4e cancel. I've arranged ...
March 21, 2015

science
I agree
March 21, 2015

chemistry
I would choose RbOH and CH3COO^- RbOH is a strong base, CH3COO^- is the base part of acetic acid.
March 21, 2015

chemistry
OH groups in inorganic chemistry are basic. I see two of them. NH3 is a base, also, but it is a weak one.
March 21, 2015

chemistry
D is right.
March 21, 2015

chemistry
B isn't right and you should know not to pick that. pH of 7.51 is basic and this is an acid. If you will show your work I will find where you went wrong.
March 21, 2015

chemistry
Can you write and balance the molecular equation? If so, do that, convert to complete ionic equation, then cancel materials common to both sides and you have the net ionic equation. Go as far as you can and I can help you finish.
March 21, 2015

English
Well, EXCUSE ME P/m; I learn something new every day. From the way those posts have read and the problems encountered by Writeacher, Reed, and Ms Sue over the last two or three days, I assumed we were trying to deal with someone not doing well with their ESL and I was trying ...
March 21, 2015

English
I know I'm butting in where I don't belong but I think a vital point is missing here and/or not being considered. It appears to me that m has trouble with the English language. Students that don't speak/write English very well can't fix what they don't ...
March 21, 2015

Science
Yes, 1 and 2 are right.
March 21, 2015

Science
You have far too many questions for one post. Here is the information for the first one. pH < 7 = acid pH > 7 = base pH = 7 = neutral.
March 21, 2015

Chemistry
To raise to the 1/4 power I use 0.25 etc. That parenthesis thing gets confusing to me.
March 21, 2015

Chemistry
Your button just isn't called the y^x button but you see you raised 12.5 to the 1/3 power. I don't do that. I plug in 12.5 and raise it to the 0.3333 power and that way I don't worry about the parentheses.
March 21, 2015

Chemistry
.........N2 + 3H2 ==> 2NH3 E........1.2....x......0.015 Kp = p^2NH3/pN2*p^3H2 Your set up is right; you're not doing the algebra right. To take the cube root you don't divide by 1/3; you hit the y^x button and use 0.3333 for the x. That gives you 2.3 atm. Try these ...
March 21, 2015

Chemistry
I2 + 6H2O ==> 2IO3^- + 10e + 12H^+ OCl^- + 2e + 2H^+ ==> Cl^- + H2O Multiply equation 1 by 1 and equation 2 by 5 and add, then cancel any common materials on both sides (like H2O) I think your error was in not comparing apples with apples; ie. I2 can't go to IO3^-. ...
March 21, 2015

Chemistry
If HCl is in excess, calculate how much excess in mols, divide by the TOTAL volume at that point to obtain (HCl) in mols/L; ie., M, then pH = -log(HCl) since HCl is a strong acid and ionizes 100%.
March 21, 2015

chemistry
You have the pKa values wrong. pK1 = 2.15; pK2 = 7.2 (which you have right) and pK3 = 12.1. Use the Henderson-Hasselbalch equation. pH = pk2 + log (base)/(acid) 7.5 = 7.2 + log (base)/(acid) or 7.5 = 7.2 + log b/a H3PO4 + NaOH ==> NaH2PO4 + H2O NaH2PO4 + NaOH ==> Na2HPO4...
March 21, 2015

Chemistry
I assume that Kzny is Kf for ZnEDTA = 3E16. millimols Zn = 50 x 0.2 = 1.00. millimols EDTA = 20 x 0.05 = 1.00 .......Zn^2+ + EDTA ==> ZnEDTA I......1.00....1.00......0 C.....-1.00...-1.00......1.00 E......0........0........1.00 With such a large Kf of 3E16, it is reasonable...
March 21, 2015

chemistry
dG = dH - TdS dG is the total; dS is just a part. dS contributes its part but clearly it must be added into dH before one knows the total energy of the system.
March 21, 2015

chemistry
Why did you change screen names from Muli to Joseph? dG = -RTlnKp Substitute and solve for Kp. By the way, remember dG goes in the equation as J/mol.
March 21, 2015

Chemistry
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know molar mass and n, solve for grams.
March 20, 2015

Science
The switch and the lamp are connected in series.
March 20, 2015

chemistry
mols SO3 = grams/molar mass = ? mols H2O = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols SO3 to mols H2SO4. Do the same and convert mols H2O to mols H2SO4. In limiting reagent problems the SMALLER amount of product formed is ALWAYS the ...
March 20, 2015

Science!
I don't agree with 5,6,9. The others are right except for 10. See my note below about 10. I don't see the right answers to 10. Evaporating the WATER (OR SOLVENT) I would buy but you can't evaporate the mixture. Using a filter will not do it nor will using a magnet ...
March 20, 2015

chemistry
Probably dipole-dipole.
March 20, 2015

Science
In parallel, each switch controls each lamp. In series any switch controls all of the lamps.
March 20, 2015

chem
mols SbCl5 = grams/molar mass = ? M = mols/5.0L = approx 0.007 but that's an estimate. ............SbCl5 ==> SbCl3 + Cl2 I...........0.007.......0......0 C............-x.........x......x E..........0.007-x......x......x Substitute the E line into the Keq expresson and ...
March 20, 2015

Chemistry
NaOH + HOOCCH3 ==> NaOOCCH3 + H2O millimols CH3COOH = mL x M = ? millimols NaOH = mL x M = ? Can you take it from here. If not please explain in detail what you don't undrstand.
March 20, 2015

Chemistry
Sample size in the titrated sample (25 mL) is 0.5 x 25/100 = ? mols EDTA = M x L = ? mols Zn = mols EDTA grams Zn = mols Zn x atomic mass Zn %Zn = (mass Zn/mass sample in 25 mL)*100 = ?
March 20, 2015

Chemistry
I need some help. What do you not understand about these questions? Both are bases and Mg(OH)2 does not form complex ions.
March 20, 2015

Chemistry
g = mols x molar mass = ?
March 20, 2015

Chemistry
use the dilution formula. mL1 x M1 = mL2 x M2 3*4 = 50*x solve for x
March 20, 2015

Chemistry
mols ethanol = grams/molar mass = ? Then M = mols/L or mols/0.250 = ?
March 20, 2015

chemistry
138 pm = 138E-12 m wavelength = h/mv
March 20, 2015

Chemistry
%MgSO4 in MgSO4.7H2O = [(molar mass MgSO4/molar mass MgSO4.7H2O)]*100 = ? Then 2.4g x (%MgSO4/100) = ?
March 20, 2015

Science
I wouldn't go that route. I think this route is easier to see. First, determine the molarity of the inital formaldehyde solution. Thats 1.037 g/mL x 1000 mL x (37/100) x (1 mol/30 g) = about 12.8 M Then use the dilution formula of mL1 x M1 = mL2 x M2 For the first dilution...
March 20, 2015

chemistry
I assume you made a typo. Technically there will not be any C+2 nor any C- ions. There is 1 mol Ca ion in 1 mol CaCl2 and 2 mols Cl^- in a mol of CaCl2. So if you start with 3.5 mols CaCl2 you will have 3.5 mols Ca^2+ and 7 mols Cl^-
March 20, 2015

chemistry
Convert pH to (H^+). Work this by the fractional method. alpha o = (H^+)^3/D alpha 1 = (H^+)^2*k1/D alpha 2 = (H^+)^k1k2/D alpha 3 = k1k2k3/D D is (H^+)^3 + (H^+)^2*k1 + (H^+)*k1k2 + k1k2k3 Then (H3PO4) = alphao*15 mM (H2PO4^-) = alpha1*15 mM etc.
March 20, 2015

Chemistry
C'mon Eevee. NaCl is not the only salt. If we call citric acid H3C, then the monosodium salt will be NaH2C. The pH of that salt in solution will be determined by the hydrolysis of the salt. ...........H2C^- + HOH ==> H3C + OH^- I..........0.15............0......0 C...
March 20, 2015

Chem
The "reversible" reactions you write are not balanced. You should place a 2 for CrO4^2- in the first one. For the bottom row of three equations, I will call them eqn 1, eqn 2 and eqn 3. Reverse eqn 2. Add to 2x the reverse of eqn 3 Add to 2x eqn 1. When you reverse ...
March 20, 2015

Chemistry
H2O(l) ==> H2O(s) delta S rxn = S(solid) - S(liquid) delta S will be in J/mol. Convert that to 5.00 grams. That gives you dS for the system. dS surrounds = - dHfusion/T (and T is 273, not zero). dS total = dSsystem + dSsurroundings. reactions are spontaneous is dS total is +.
March 20, 2015

Chemistry- Electrochemistry
Ecell = Eocell -0.059/n*log Q
March 20, 2015

Chemistry
p1v1 = p2v2
March 19, 2015

Chemistry
I don' know what the question is. What does "Both A and D above are correct" mean.
March 19, 2015

chemistry
Use PV = nRT, substitute the conditions and solve for n = number of mols. Then n = grmas/molar mass. You know mols and grams, solve for molar mass. Look on the periodic table and identify the gas.
March 19, 2015

To Cortney---Chemistry
I see you answered your own question and that's ok with me; however, it is not ethical to type in my name as the author of that answer. I didn't answer that question. My computer shows you used the same computer to type the question and answer. Shame on you for trying ...
March 19, 2015

chemistry
The answer is a
March 19, 2015

chemistry
The one most likely to be a gas at room T is F2 LiF is likly to be soluble in water because both are polar; polar solutes dissolve in polar solvents. LiF is polar; PCl3 is polar. F2, BeF2, CCl4 are not polar.
March 19, 2015

chemistry
Do you know which are ionic and which covalent? That is the secret to answering this question. LiF is ionic, it dissolves in H2O and because the ions are in solution it conducts electricity.
March 19, 2015

Chemistry
I believe I is true. I think II is true. III is true sometimes but not always. I would agree if it said attracted to other polar molecules. It doesn't say that so I would rule III out. IV is not true.
March 18, 2015

chemistry
mols CaCl2.2H2O = grams/molar mass = ? There is 1 mol of CaCl2 in 1 mol CaCl2.2H2O
March 18, 2015

chemistry
What's the reaction?
March 18, 2015

Chemistry
1. You can convert any mole in an equation to another in the same equation just by using the coefficients in the balanced equation. 0.45 mols N2 x (2 mols NH3/1 mol N2) = 0.45 x 2/1 = ?. This will always work. The numberator is what you want to convert to and the denominator ...
March 18, 2015

chemistry
Take a 100 g sample to give you 63.9 g CuSO4 and 36.1 g H2O Convert to mols. mols CuSO4 = grams/molar mass = ? mols H2O = grams/molar mass = ? Now find the ratio of the two with the smaller number no less than 1.00. The easy way to do that is to divide the smaller number by ...
March 18, 2015

Chemistry I
M = mols ethanol/L solution. What else do you need to know?
March 18, 2015

Chemistry
Use k1 and solve for (H^+) = (H2AsO4^-) Use k2 to solve for (HAsO4^2-) Use k3 and your numbers from 1 and 2 to solve for AsO4^3-. Note: you may need to use a quadratic for the first part (k1). Post any work if you get stuck.
March 18, 2015

Chemistry
You shouldn't find this that hard. Look at your original data. How did you determine mols initially. Wouldn't you think that if you doubled the vinegar at the start you would have double the mols? b. Wouldn't you think it you took x mL to tirate the 25 that it ...
March 18, 2015

chemistry
Calculate %H2O in CaSO4.2H2O by (2*molar mass H2O/molar mass CaSO4.2H2O)*100 = ? 8.60g sample x %H20/100 = grams H2O driven off. Convert to mols. Then use PV = nRT and the conditions listed and solve for V in Liters.
March 18, 2015

rate law chem
I wouldn't think so. The order may be different, the coefficients may be different.
March 18, 2015

CHEM
I assume you titrated the acetic acid with a base such as NaOH or KOH. If that is the case, moles acetic acid = mols NaOH and mols NaOH = M x L = ?
March 18, 2015

Chemistry1412
To solve for x do (0.110)(x^3)(9.6) = (0.134)^2 x^3 = (0.134)^2/9.6*0.110 = ? Then x = cube root of ?
March 18, 2015

Chemistry1412
If these are equibrium concentrations that is right.
March 18, 2015

Chemistry1412
136.54 looks ok but that's too many significant figures. I would round it to 136. As to your other what if question, you can do (CH3OH) but only if you have Kc (unless someone tells you that the reactions goes to completion). In that case it becomes a regular stoichiometry...
March 18, 2015

Chemistry1412
What's your trouble with this problem? It's just a matter of substituting the values into Kc expressions.
March 18, 2015

chemistry
I don't like any of the answers. The reason a gas exerts pressure is because of collisions of the particles with the walls of the container. I would go with c easily if it added, "Collisions......gas WITH THE WALLS OF THE CONTAINER."
March 18, 2015

Chemistry
Print this out. This 4-step procedure will work all of this type. 1. Write and balance the equation. 2. mols HNO3 = M x L = ? 3. Use the coefficients in the balanced equation to convert mols HNO3 to mols Ba(OH)2. 4. Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2
March 18, 2015

Chemistry1412
Kp for the rxn is 2.26E4 For the reverse it is 1/Kp For 3x the rxn it is (1/Kp)^3
March 18, 2015

chemistry
You made a typo; you have too many zeros in that 226000 don't you? The answers looks ok.
March 18, 2015

chemistry
Answered above.
March 18, 2015

Chemistry
Use P*molar mass = density*RT Solve for molar mass. Then empicical formula mass x x = molar mass Solve for x which is (empirical formula mass)x which is (CH2)x or it can be re-written as CxH2x for the molecular formula.
March 18, 2015

chemistry
Use PV = nRT and solve for n CO2 (mols CO2). Do the same for n H2O. The wording is confusing. Do you want the mass of the reaction as is or do you want it balanced first. I would think balanced first, then the mass of the balanced equation. If so, then balance the equation. ...
March 18, 2015

chemistry
E = 2.180E-18(1/2^2) joules.
March 18, 2015

chem
If you can give us some hints as to what you don't understand about all of these questions someone here may be able to help. You can google most of the answers.
March 18, 2015

Chemistry
nFEocell = RTlnK
March 18, 2015

chemistry
1 and 2 are right. I'm not an internal combustion man but I think the answer is c. The compression stroke is when the piston is at the bottom of it's stroke and it has just pulled in the fuel, then it starts up and compresses the gas so that the gas occupies the ...
March 18, 2015

chemistry
6.02E23 atoms Cr = 52 g. So 1E6 Cr atoms will have a mass of .....?
March 18, 2015

Chemistry
I didn't answer this last night because I really didn't like any of the answers. I,like Jai, think the best answer is c. I would have liked it better if the answer for c had been stated as, The NaCl CRYSTAL is surrounded by water molecules. I thought perhaps the fact ...
March 18, 2015

Chemistry
I think you made a typo with that Cu(NO3)4^2. I assume you meant [Cu(NH3)4]^2. 18.8 g Cu(NO3)2 = ?M. That's mols = grams/molar mass. Let's call that about 0.1 but you should go through and confirm that. ........Cu^2+ + 4NH3 ==> [Cu(NH3)4]^2 I....... 0.1....0.400...
March 17, 2015

chemistry
yes
March 17, 2015

chemistry
I think the easy way to do this is as follows: It reuires 129 kJ to decompose 2 mol NaHCO3 so it should require 129 x 3/2 to decompose 3.5 mols. The difference in where the dH is written is the sign. If you write it as you have above, it means the rxn is endothermic and you ...
March 17, 2015

Physical Science
http://chem-guide.blogspot.com/2010/04/cracking-and-reforming.html
March 17, 2015

Chemistry
I think if you just balance the equation things will work out. 2I^- + O3 ==> 3H2O + I2 I goes from -2 total to 0 for 2 I. O goes from 0 to -6 total for 3 O. Multiply I part by 3 and O part by 1 so equation becomes 6I^- + O3 ==> 3H2O + 3I2 Now balance the charge by ...
March 17, 2015

Chemistry
Yes, D.
March 17, 2015

chemistry
I agree
March 17, 2015

chemistry
XCO2 = mols CO2/total mols. XCO = mols CO/total mols XO2 = mols O2/total mols. pCO2 = XCO2*Ptotal pCO = XCO*Ptotal pO2 = XO2*Ptotal
March 17, 2015

chemistry
First, your equation isn't balanced. Balance it. mols C6H12O6 = grams/molar mass = ? Using the coefficients in the balanced equation convert mols C6H12O6 to mols O2. Then use PV = nRT and convert mols O2 to volume in L at the conditions listed.
March 17, 2015

Chemistry
Which atom are you talking about?
March 17, 2015

chemistry
I don't think that will do it. The Law of Conservation of mass says everything on the left must equal everything on the right. 2.241 + x = 2.852. X = ?
March 17, 2015

Chemistry
HNO3 + KOH ==> KNO3 + H2O mols HNO3 = M x L = 0.06 pH = 2.5 means you want (H^+) to be 0.00316 or mols (H^+) = 0.00316 x 0.4L = 0.00126. That's mols (H^+) remaining which means you must neutralize the difference; i.e., 0.06 - 0.00126 = ? Convert that to grams KOH.
March 17, 2015

Chemistry
All of these hydrolyze (actually NaCl does not) like this. ..........A^- + HOH ==> HA + OH^- I.......0.1..............0....0 C........-x..............x....x E......0.1-x.............x....x Kb for base = (Kw/Ka for HA) = (HA)(OH^-)/(A^-) Substitute Kw, you have pH, I would ...
March 17, 2015

Chemistry
PV = nRT; solve for n = number mols Ar + Ne in the 2L vessel at the conditions listed. PV = nRT in container B; solve for n = number of mols Ne. Subtract total mols - mols Ne to give you mols Ar. Then PV = nRT in container A; You have P, n, R, T; solve for V at the conditions ...
March 16, 2015

Chemistry
Not much else to do than to work the problem. The point you are missing is that it's a strong acid. Strong acids ionize 100% so ALL of the HCl molecules end up as ions and NONE are in the form of HCl molecules. It isn't necessary to do an ICE chart but that might help ...
March 16, 2015

chemistry
Ksp = (Pb^2+)(I^-)^2 Substitute Ksp and I (I^- = 1.1E-4M) and solve for (Pb^2+)
March 16, 2015

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