Friday
January 30, 2015

Posts by DrBob222


Total # Posts: 46,649

chemistry
55.5 mols/L
January 12, 2015

Chemistry (Acid-Base)
Look up the density of water at 25C and use that to calculate the mass of 1000 mL. Ifound density at 25 C = 0.99705 g/mL; therefore 1000 mL has a mass of 997.05g.Then mols H2O = grams/molar mass = 997.05/18.015 = about 55.35 M
January 12, 2015

Chemistry (Acid-Base)
I must confess that I've never heard the term "protonation constant" used. Logic tells me this might be the reciprocal of Ka, the dissociation constant but I don't know that. Can you shed some light? If we can define what the protonation constant is I can help.
January 12, 2015

Science
http://en.wikipedia.org/wiki/Tide
January 12, 2015

chemistry
Al2O3. mols Al2O3 = grams/molar mass = ? Since there are two Al atoms in a molecule of Al2O3, twice that will be mols Al. Then remember that 1 mol of Al contains 5.02E23 atoms Al.
January 11, 2015

Chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. Fe3O4 + 2C ==> 2CO2 + 3Fe mols Fe3O4 = grams/molar mass = ? mols C = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe3O4 to mols Fe. Do ...
January 11, 2015

chemistry college
This is a direct relationship and I think that is easier to use here than going through the p = KcC or C = KpP. 0.169 g/100 x (43,000/760) = ?
January 11, 2015

Chemistry
First, note that you can't throw all of those numbers after 0.0049 away. You have 4 places in 0.4835 and you should have AT LEAST 4 in the answer. I usually carry one more place and round at the end. Ca^2+ + EDTA ==> Complex mols EDTA = mols CaCO3 Then M EDTA = mols/L ...
January 11, 2015

Chemistry
http://www.jiskha.com/display.cgi?id=1421013794
January 11, 2015

Chemistry
3 x that for K 1 x that for P 4 x that for O
January 11, 2015

chemistry
28000 = mass ice x heat fusion. Subsitute heat fusion in calories/g and solve for mass of ice in grams.
January 11, 2015

Chemistry
When gases are involved one may use stoichiometry as if volume = mols. 800 cc O3 x (3 mols O2/2 mols O3) = 800 x 3/2 = ? cc O2
January 11, 2015

chemistry
.........N2(g) + 3 H2(g) ⇀↽> 2 NH3(g) E.......3.1M......0.8M..........x K = 5.2E-5 = (NH3O^2/(N2)(H2)^3 Plug the equilibrium numbers into Keq and solve for (NH3) in mol/L. Convert to mols in 10 L and convert that to grams.
January 11, 2015

CHEM
What's your problem. Write the Keq expression, substitute the equilibrium numbers in the problem, and solve for Keq. If you still can't do it explain fully what you don't understand.
January 11, 2015

CHEMISTRY
.........N2(g) + 3 H2(g) ⇀↽> 2 NH3(g) I.........2M........1M..........2M C........-2x........-3x.........2x E..........?.......2.53M.........? Since we know eq (H2) = 2.53, that means that H2 was formed, the reaction is proceeding from right to left and that ...
January 11, 2015

Chemistry
The pH et al are determined by the hydrolysis of the CN^-. ........CN^- + HOH ==> HCN + OH^- I......0.5..............0.....0 C.......-x..............x.....x E.....0.5-x.............x.....x Kb for CN = (Kw/Ka for HCN) = (x)(x)/(0.5-x) You know or can look up Kw for H2O and ...
January 11, 2015

chemistry
Fair warning. Many of us, me in particular, shy away from posts containing more than one question. It takes too long to answer a single question and some of us have just time enough some times to knock off one small question. In this case the answers were quick and I did them...
January 11, 2015

chemistry
See your duplicate above.
January 11, 2015

chemistry
or 125 mL.
January 11, 2015

Chemistry
This is a limiting reagent (LR) problem and I know this because amounts are given for BOTH reactants. Therefore, one will be used completely (the LR) and the other will have some un-reacted. Hg + Br2 ==> HgBr2 Use density to convert mL Hg to grams. Do the same for mL Br2 to...
January 11, 2015

Chemistry
Take a 100 g sample to give you 65.5 g C atoms 5.5 g H atoms 29.0 g O atoms Convert each to mols. mols = grams/molar mass C = 65.5/12 = estimated 5.5 H = 5.5/1 = 5.5 O = 29.0/16 = about 1.8 Now find the ratio of the elements to one another with the smallest whole number being ...
January 11, 2015

Chemistry
dHrxn = (n*dHo products) - (n*dHo reactants) dSrxn = (n*dSo products) - (n*dSo reactants) dGrxn = dH - TdS Post your work if you get stuck.
January 11, 2015

Chemistry
Fe(s) + CuSO4(aq) ==> FeSO4(aq) + Cu(s) The only problem I see with the question is the example. The question concerns a single replacement reaction and the example is a double replacement reaction. The two are not the same. I know, the form is to show how the states are to...
January 11, 2015

Chemistry
Did you transpose the numbers? I obtained 6.5 g.
January 11, 2015

Chemistry
This IS the simple way. The basic concept is that 1 mole of anything contains 6.022E23 anythings; i.e., 1 mol N contains 6.022E23 atoms of N, 1 mol N2 contains 6.022E23 molecules of N2, 1 mol of U contains 6.022E23 atoms of U, 1 mol of eggs contains 6.022E23 eggs (that's a...
January 11, 2015

Chemistry
1 mol N2 = 2*14 g N2 contains 6.022E23 molecules N2. How many moles N2 do you have? That's 1.40E23 molecules x (1 mol/6.02E23 molecules) = ?# mols N2. Then since 1 mol N2 contains 28 g, how much will ?# moles weigh?
January 11, 2015

Chemistry
C = amperes x seconds C = 4.00 x 1 hr x (60 min/hr) x (60 s/min) = ? 96,500 C will deposit 107.9 g Ag. 107.9 g Ag x (? C from above)/96,500 = ? g Ag deposited.
January 11, 2015

chemistry
Mg + Cu(Ac)2 ==> Mg(Ac)2 + Cu mols Cu(Ac)2 = M x L = ? Using the coefficients in the balanced equation, convert mols Cu to mols Mg. Now convert mols Mg to g Mg. g = mols x molar mass. This is the theoretical yield (TY). The actual yield (AY) is 6.00g % yield = (AY/TY)*100 = ?
January 11, 2015

Chemistry
Your use of c1v1 = c2v2 is ok but I don't think you punched in the right numbers. Or set it up wrong. 0.1 x 0.0015 = C2 x 0.5 C2 = ? And yes, you use C2 to solve for pH. I obtained about 3.5(estimated)
January 11, 2015

Chemistry
I assume that is 10.65 g Zn with 23.75 A. 96,485 will deposit 65.38/n g Zn. That's 65.38/2 = 32.69 g Zn. You want 10.65g Zn. How many C is that? C = 96,485 x 10.65/32.69 = ? Then C = Amperes x seconds You know C and A, solve for seconds.
January 11, 2015

Chemistry
Ecell = Eocell - (0.0592/2)*log K Do you have all of the information you need? Is Ecell 0.35v? If so what is Eocell?
January 11, 2015

chemistry
And what is your trouble with the question. Do you have the activity series of metals? Do you know what that means? Can you write the equation after you know which ones will/will not react?
January 11, 2015

chemistry
At 407 the Zn metal vapor is at the boiling point. First it must be condensed (at 407C) to become a liquid. Cooled to 425 it hasn't frozen yet so it is still a liquid. q1 = heat released on condensing the Zn vapor. q1 = mass Zn vapor x heat vaporization/condensation. q2 = ...
January 11, 2015

chemistry
What's the freezing point and boiling point of Zn? You need those to work the problem.
January 11, 2015

Chemistry
NaHCO3 + CH3COOH ==> CH3COONa + H2O + CO2 The hope is that the bubbling CO2 gas will unclog the drain. NaOH is a very good drain opener but it is so caustic and can cause severe damage if it gets on the skin or in the eyes.
January 11, 2015

Chemistry
molecular equation: HBr(aq) + KOH(aq) ==> KBr(aq) + H2O(l) total ionic: H^+(aq) + Br^-(aq) + K^+(aq) + OH^-(aq) ==> K^+(aq) + Br^-(aq) + H2O(l) net ionic equation: just cancel the ions common to both sides. What's left is the NET ionic equation. H+(aq) + OH^-(aq) ==&...
January 11, 2015

ap chemistry
Use density to calculate mass H2O. mass = volume x density. Calculate mole fraction H2O n H2O = grams/molar mass n glycerin = grams/molar mass ntotal = n H2O + n glycerin XH2O = n H2O/n total psoln = XH2O*PoH2O Post your work if you get stuck.
January 11, 2015

chemistry
Yes, I think you did.
January 11, 2015

chemistry
All liquids and gases exhibit Brownian movement. That is the random movement of individual atoms/molecules in a liquid or gas. Any gas or liquid is an example; if you mean an example you can see you must make the atoms/molecules visible Place some finely ground silt (dirt) in ...
January 11, 2015

chemistry
Pb(NO3)2 + 2KI ==> PbI2 + 2KNO3 mols Pb(NO3)2 = M x L = ? Using the coefficients in the balanced equation, convert mols Pb(NO3)2 to mols PbI2 ppt. Now convert mols PbI2 to grams PbI2. That's grams = mols x molar mass = ? That is the theoretical yield (TY). The actual ...
January 11, 2015

chemistry
It looks good to me too; however, I should point out that it has been shown that NH4OH does not exist. It is NH3(aq). In water solution it does this NH3 + HOH --> NH4^+ + OH^- It still is an Arrhenius base because it produces OH^- in solution. I don't know the exact ...
January 10, 2015

Chemistry-Paramagnetic or Diamagnetic
An element is paramagnetic if it has unpaired electrons. It is diamagnetic if it has all of its electrons paired. It is is paramagnetic it will be attracted to an applied magnetic field; it will be repelled if it is diamagnetic. Here is a good site to visit. Post back if you ...
January 10, 2015

Chemistry
And I obtained 72 also but that isn't right. I left out the C = 12 That Na + H + C + 3O 23 + 1 + 12 + 3*48 = 84.
January 10, 2015

Chemistry
NaHCO3 = 1*23 + 1*1 + 3*16 = ?
January 10, 2015

Chemistry
I don't get 6.25. molar mass C2H8O4 = about 96 but you can look it up more accurately if you wish. Then mass H is 8 (again you can be more accurate if you wish) Then (8/96)*100 = about 8.3%. Please note. I looked up the formula for aspirin and I didn't get what you ...
January 10, 2015

Chemistry
molar mass aspirin = ? 2*12 + 8*1 + 4*16 = ? % H = (mass H/total mass)*100 = ?
January 10, 2015

ap chemistry
I guess I could buy into that.
January 10, 2015

Chemistry grade 11
When you have a problem like this why don't you post your work and we tell at a glance what is wrong. I worked the problem and obtained an empirical formula of 30 which gives a molecular formula of (CH2O)5 [or C5H10O5] for a molar mass of 150. I can help you through it if ...
January 10, 2015

Chemistry grade 11
Would you look at your post and confirm the molar mass of 14 g/mol. If you have the simplest formula possible of CHO, the molar mass of that is 12+1+16 = 29 so I don't believe 14.
January 10, 2015

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O mols Ba(OH)2 = M x L = 0.320 x 0.050 = 0.016 heat released = mass H2O x specific heat H2O x (Tfinal-Tinitial) q = 100 x 4.184 x (26.16-21.80) = ? q/0.016 = q/2 mol H2O so divide by 2 for q/1 mol H2O produced and add a negative sign since heat...
January 10, 2015

Chemistry
pH = -log(H^+) 9.2 = -log(H^+) -9.20 = log(H^+)
January 10, 2015

Chemistry.
Yes, the ratio is always in whole number; however, one must be careful not to throw away too much. For example if the number comes out to be 2.05 it can be rounded down to 2.0 but if the number is 2.5 that can't be rounded to either 2.0 or 3.0. if the ratio was 1.0 to 2.5 ...
January 10, 2015

chemistry
What are you thinking. What are your ideas?
January 10, 2015

chemsitry
Suppose you had a sample of MgSO4.7H2O that weighed 61.62g before heating an 30.1 after heating. loss in weight is 61.62-30.1 = 31.52 30.1 is the mass H2O lost. 30.1 is the mass MgSO4 without the water. molar mass MgSO4 = 120.37 molar mass H2O = 18 mols = g/molar mass mols ...
January 10, 2015

ap chemistry
http://www.jiskha.com/display.cgi?id=1420918696
January 10, 2015

college chemistry
See your post above.
January 10, 2015

ap chemistry
Tell us what you think.
January 10, 2015

Chemistry
How much 3% do you want to make? Let's say you want 100 mL. c1v1 = c2v2 99*v = 3*100 solve for v of the 99%
January 10, 2015

Chemistry
The standard is in the second part. A = abc A = 1.220 a = ? b = 2 c = 23.4 ppm a = A/bc = ? Then for the unknown, A = abc. You know A = 0.832, a(from the calculation above), and b = 2 cm. Solve for c of the unknown in ppm.
January 10, 2015

Chemistry (Electrochemistry)
96,485 C will stip 107.9 g Ag. 107.9 x 0.600/96.485 = g Ag stipped g = v x d. You know g and d, solve for volume. Area of the unmasked section is A = pi*r^2 = pi*(0.5/2)^2 = ? volume = A * thickness. You know volume and you know A, solve for thickness in cm and convert to um. ...
January 10, 2015

Chemistry
First off I think it is important for you to realize that you are not using (or thinking about) an ordinary balance. This mass measurement must be used in conjunction with an externally applied magnetic field. If the element has unpaired electrons it is paramagnetic and will ...
January 9, 2015

Chemistry
For every one Fe(NO3)3 molecule you have you get three NO3^- ions when the molecule dissociates. So the (NO3^-) is 23.1 ppm x 3 = ?
January 9, 2015

science
q1 = heat removed in changing T from steam at 122 to steam at 100. q1 = mass steam x specific heat steam x (Tfinal-Tinitial) q2 = heat removed on condensation at 100 C to water at 100 C. q2 = mass steam x delat H(heat condensation) q3 = heat removed in changing T of liquid ...
January 9, 2015

Chemistry
The procedure I wrote and the one Devron wrote is essentially the same. Assuming the reaction proceeds, the correct balanced equation is 2Al(NO3)3 + 3K2SO4 ==> Al2(SO4)3 + 6KNO3
January 9, 2015

Chemistry
I don't think any Al2(SO4)3 will be produced because there is nothing to drive the reaction. The reasons for a reaction are 1. gas is formed. none here 2. ppt formed. everything soluble here. 3. Slightly ionized material. not true here. But in the spirit of the question ...
January 9, 2015

Chemistry
w of Na2CO3 = 105.94, Thus moles Na2CO3 = 1.234/105.94 = 0.011. My calculator gives 0.011648. Why did you throw those other numbers away? You have 4 significant figures in 1.234 so you should be able to have AT LEAST 4 places and I like to carry one extra place--then round a ...
January 9, 2015

ap chemistry
Which was the solute and which the solvent? I'm assuming from the question I answered last night about lauric acid that the lauric acid is the solute and benzoic acid is the solvent. (1)delta T = Kf*m (2) m = mols/kg solvent (3) mols = grams/molar mass Follow from the ...
January 8, 2015

Chemistry 1010
mols AgNO3 = L x M = 0.0700 x 0.692 = ? Use the coefficients in the balanced equation to convert mols AgNO3 to mols Ag2CO3. That's ? mols AgNO3 x (1 mols Ag2CO3/2 mols AgNO3) = ? mols AgNO3 x 1/2 = ? Then g Ag2CO3 = mols Ag2CO3 x molar mass Ag2CO3.
January 8, 2015

chemistry PLEASE HELP URGENT
I'll do the middle one. 0.2 mols/L (NH4)2SO3 The cation is NH4^+ For every 1 mol (NH4)2SO3 you have 2 mols NH4^+; therefore, (NH4+) = twice the (NH4)2SO3 and that give 0.2 mols/L x 2 = 0.4 mols/L = 0.4 M. a is Na2CO3 formula. c is Fe2(SO4)3 formula.
January 8, 2015

Science
I don't see two equations. I think I may see your problem. H3PO4 is not one equation and H4P2O7 a second. H3PO4 is part of an equation and H4P2O7 is another part of an equation. To answer your question, however, you're right about H3PO4. H4P2O7 has 4 H atoms, 2 P atoms...
January 8, 2015

chemistry
I believe the answer provided by this solution is three times too large. The problem asks for grams Na3PO4 to provide 0.25 M SODIUM ION. Since there are 3 Na ions per Na3PO4 molecule you need to divide 0.25/3 to begin with, then proceed s in the above.
January 8, 2015

chemistry
Co is 1s2 2s2 2p6 3s2 3p6 3d7 4s2 Co^2+ is 1s2 2s2 2p6 3s2 3p6 3d7 For the d orbitals draw 5 boxes. I can't do this on this forum but 5 boxes in a line (row). The boxes look like this for Fe and Fe^3+. https://www.google.com/search?q=Co+orbital+boxes&tbm=isch&tbo=u&source=...
January 8, 2015

chemistry
In what? mols/L, M, g/L, etc. I'll assume M or moles/L. moles (NH4)2CO3 = grams/molar mass = ? Then mols NH4^+ = 2 x mols (NH4)2CO3. M = mols NH4^+/L = ?
January 8, 2015

Chemistry
This is not a dilution problem. mols KHP = grams/molar mass = ? mols NaOH = mols KHP M NaOH = mols NaOH/L NaOH Solve for L NaOH and convert to mL.
January 8, 2015

chemistry
I see from another post that you are asking about the weight. I also note you seem to be using the weight of a lemon and the pure lemon juice almost interchangeably. You know, of course, they are not the same. Did you weigh the whole lemon? That's not pure lemon juice. Did...
January 8, 2015

chemistry
And think you are right. I think the density of pure lemon juice is fairly close to that of water. Perhaps the lemon juice you used has seeds? or pulp? I think 1.36 g/mL sounds high to me. In answer to your last question no, it means the answer should be closer to 1.0 g/mL. Or...
January 8, 2015

SCIENCE
I don't see a question here.
January 8, 2015

sdvfsd
Probably the longest sentence I've ever seen but I don't see a question.
January 8, 2015

lauric acid
http://www.jiskha.com/display.cgi?id=1420733562
January 8, 2015

science
You can't calculate it without numbers, other than looking it up. Post your question instead of trying to summarize it. You've posted the question with no details.
January 8, 2015

Chemistry
4.5 mols C will produce 4.5 mols CO2 at STP. One mole CO2 occupies 22.4 L at STP so 4.5 mols CO2 will occupy .....?
January 8, 2015

Chemistry
2Fe2O3 + 3C ==> 3CO2 + 4Fe 5.6 mols Fe2O3 x (3 mols C/2 mol Fe2O3) = 5.6 x 2/3 = ?
January 8, 2015

Chemistry
Oxidation is the loss of electrons. Cu goes from zero on the left to 2+ on the right. Cu ==> Cu^2+ + 2e Reduction is the gain of electrons. Ag goes from +1 on the left to zero on the right. Ag^+ + e ==> Ag
January 8, 2015

ap chemistry
(1)delta T = Kf*m Substitute delta T and Kf; solve for m (2)m = mols/kg solvent Substitute m and kg solvent; solve for mols (3)mols = grams/molar mass. Rearrange to molar mass = grams/mols. Now follow through with equation 1, 2, and 3. If some of the lauric acid (but you have ...
January 8, 2015

oops-typo---Chem-Stoich
Ignore the last line. I don't know how it got posted; it shouldn't be there. The rest of the problem is ok.
January 7, 2015

Chem-Stoich
mmol = millimole mmol HCl initially = mL x M = 35.00 x 1.00 = 35.00. mmols NaOH used to titrate excess is 31.51 x 0.0950 = 3 approx but you need to do a more accurate calculation. All of the other numbers that follow are approximations, too, so you need to redo all of this ...
January 7, 2015

chemistry
See your post below.
January 7, 2015

chemistry
I don't think you have enough information. dG = dH - TdS At boiling, dG = 0 Then TdS = dH and dS = dH/T = 540/373 but that gives you cal/g and you want cal/mol. Without knowing the molar mass (I assume this is water but the problem doesn't say that), I can't ...
January 7, 2015

Science
Probably not. I think it wants the number of DIFFERENT atoms (H,S,O or 3) and the total number of atoms.7. The question isn't worded very well.
January 7, 2015

chemistry
Don't you think that is proprietary information?
January 7, 2015

colligative
I don't understand the question I don' think. You use a thermometer to measure T.
January 7, 2015

ap chemistry
I get 2.00 atm also. If you have a density in the problem we can correct for and use M and not m but with no density in what you posted we have no choice but to use m for M.
January 7, 2015

ap chemistry
moles in 4.9g = grams/molar mass = ? m = molality = mols/kg solvent delta T = Kf*m. Solve for delta T and subtract from the normal freezing point of H2O (0C) to find the new freezing point. pi = MRT M is molarity but in dilute solutions M and m are almost the same. R is 0....
January 7, 2015

colligative properties
What exactly do you not understand. XH2O = 19.6/23.8 = 0.824 Then 0.824 + XCH4N2O = 1 XCH4N2O = 1-0.823 = ? You may be confused by where did I get the one. The sum of the mole fractions in EVERY solution must add up to 1. Remember 100% is all of something and that is 1 when ...
January 7, 2015

colligative properties
I answered this below.
January 7, 2015

chemistry
http://www.jiskha.com/display.cgi?id=1420508318
January 6, 2015

chemistry
After you have XH2O, then use the next equation, XH2O + XCH4N2O = 1 0.824 + X = 1 Solve for X.
January 6, 2015

chemistry
The first line is the equation you use. You know psoln = 19.6 torr and you know Po H2O is 23.8 torr. Solve for XH2O. It's as simple as 19.6/23.8 = ? Then convert to XCH4N2O.
January 6, 2015

chemistry
psoln = XH2OPoH2O Then XH2O + XCH4N2O = 1. Solve for XCH4N2O
January 6, 2015

chemistry
Answered above.
January 6, 2015

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