Saturday
October 25, 2014

Posts by drbob222


Total # Posts: 44,713

Chem
I don't think the problem is stated very well. You know without any reasoning that the percent error will increase. Surely this isn't the answer you want. It appears to me that you want an answer that is based on the final result. If all of the alum is not dissolved, ...
October 12, 2014

chemistry
mols HCl = M x L = ? mols NaOH = M x L = the same q = mass H2O x specific heat H2O x Tfinal-Tinitial). This is q for the water and calorimeter. If you want the calorimeter by itself you must look up the heat neutralization and adjust for that.
October 12, 2014

chemistry
I don't see a question here.
October 12, 2014

Chemistry
mols in 25.4g Ca = grams/molar mass = approx 0.6 but that's an estimate. mols C = approx 0.6 g C in 0.6 mols = approx mols x atomic mass.
October 12, 2014

CHEMISTRY
You're there. Since 24/1 is the EW for LiOH, then 24 g LiOH in 1L solution will be 1 N. (also 1 M) b. Same for H3PO4. Dissolve 98/3 g H3PO4 in a little water and make to the 1L mark with water to prepare a 1 N solution of H3PO4. Technically you need the reaction being used...
October 12, 2014

CHEMISTRY
This is just a dilution. mL x % = mL x % 250mL x 70% = ?mL x 100%
October 12, 2014

CHEMISTRY HELP
mols C6H12O6 = grams/molar mass = ? Then m = molality = mols/kg solvent. You know kg solvent and mols, solve for m. Then delta T = Kf*m and solve for dT, then subtract from 0 to find new freezing point. OR, delta T = Kb*m and solve for dT then add to 100 to find the new ...
October 12, 2014

Chemistry
Didn't I do this for you last night? Go back and try to find it. Post gain at the top of the page is you still have trouble.
October 12, 2014

chemistry
I worked this above at your later post.
October 12, 2014

chemistry
Zn + 2HCl ==> H2 + ZnCl2 mols Zn = mass/atomic mass Zn. I would use 690.5/65.38 = ? 1 mol Zn = 1 mol H2; therefore, ? mols Zn = same mols H2. When you know the size of the balloon or something about the volume of each balloon you can finish the problem.
October 12, 2014

chemistry
You need to clarify the problem. I think you are asking to calculate (Fe^3+) which you have mixed 1 mL of 0.00050 M FeCl3 with 9 mL of 2.0 M HCl. This is just a dilution problem. You have diluted 1 ml Of the FeCl3 with 9 mL of the HCl solution. Assuming the volumes are ...
October 12, 2014

Chemistry
We can't draw mechanisms/diagrams/pictures on this forum. I suggest you look at google. I'm sure there is on on the web. Try this site. I see some electrons being pushed. If this does'nt help use google. https://www.google.com/search?q=mechanism+aldehyde+fehling%...
October 12, 2014

To Twaha---chemistry
What you have posted is pure blarney. First error: 300 mL solution equals 5 g MgCl2 and not 0.5. The problem says 300 mL solution and 5.0 g MgCl2. Second error: you are trying to base molarity on solution/grams and it should be mols/L solution. The correct solution is as ...
October 11, 2014

chemistry
mols MgCl2 = grams/molar mass Then M = mols/L solution
October 11, 2014

CHEMISTRY
% by mass = grams solute/100 g solution or (X/600)*100 = 5.5 X = 600*0.055 = 33 g solute. You can prove that if you wish to know you're right.(33/600(*100 = right! 5.5% So how much is water and how much is solute. (If 33g is the solute, then 600-33 = ? must be H2O)
October 11, 2014

CHemistry
The molecular equation is Fe(NO3)3 + 3NaOH ==> Fe(OH)3 + 3HNO3 You can add the phases if you wish. net ionic equation is Fe^3+(aq) + 3OH^-(aq) ==> Fe(OH)3(s)
October 11, 2014

Chemistry
There's an easier way to do this but I don't have it yet so here is the long way. 1/wavelength = RZ^2(1/n^2 - 1/n^2) Solve for wavelength. R = 1.0973E7 Z = 4 The first n^2 in the formula is 1 The second n&2 in the formula is 0 So 1.0973E7*4^2((1-0) and that gives you 1...
October 11, 2014

Chemistry
2 mols Mg will produce 2 mols MgO. 2 mols MgO x molar mass MgO = grams MgO
October 11, 2014

Chemistry
2Li3PO4 + 3Ca(NO3)2 ==> Ca3(PO4)2 + 6LiNO3
October 11, 2014

Chemistry
If you just want to melt the ice and not heat up the country side you would need (grams ice x heat fusion) You will need to convert 20 L ice to grams and you can do that with density in which grams = volume x density. Look up heat fusion and multiply.
October 11, 2014

AP Chemistry
I don't think #1 is right so I believe you should rethink your other answers although I didn't look at them after #2. My reason for this response is I assume the procedure went something like this. (initial mass alum - final mass alum) = loss in mass and that is mass ...
October 11, 2014

CHEMISTRY
V2O5 + 2H2 ==> V2O3 + 2H2O
October 11, 2014

CHemistry
pKsp = 9.74 = -log Ksp Ksp = 1.82E-10 .............AgCl ==> Ag^+ + Cl^- I............solid....0.......0 C............solid....x.......x E............solid....x...... 0.1 The 0.1 for Cl^- comes from the problem Ksp AgCl =1.82E-10 = (Ag^+)(Cl^-) 1.82E-10 = (x)(0.1) Solve for ...
October 11, 2014

Chem lab
As well as what you've come up with.
October 11, 2014

Chem lab
You need to tell us what experiment you did and how you went about it.
October 11, 2014

chemistry
Two simple ways: 1. The blue or green color of the original solution is still there or 2. Let the Cu(OH)2 ppt settle and add 1-2 drops to the supernatant liquid at the top of the container and see if more ppt forms.
October 11, 2014

Chem
Total mols = mols O2 + mols N2 = 1.58 + 0.420 = ? You divided mols/molar mass to find X and that isn't right. XO2 = nO2/total mols. XN2 = nN2/total mols Then you can find partial pressure of each this way. pO2 = XO2*Ptotal pN2 = XN2*Ptotal
October 11, 2014

Chem
When you post a problem like this it does little good unless you post the constants you are using too. We are likely to use the wrong set in our book and the answer we come up may not agree with yours but both could be right with the constants we've used. As it turns out ...
October 11, 2014

Chem
I don't agree with that.I would have carried the 24.6 out another place and rounded later. That part is ok and I obtained 24.63 L; however, if you use P(Mm)= dRT you never need to go through the volume calculation since it isn't in the final equation. You just plug in ...
October 11, 2014

chemistry
This is a limiting reagent (LR) problem. You know that when amounts have been given for BOTH reactants. I'll use abbreviations alco + acetic ==> acetate + H2O mols alco = grams/molar mass mols acetic = grams/molar mass Using the coefficients in the balanced equation, ...
October 11, 2014

Dav public school
The R group donates electrons to the O atom making it more negative which makes it harder to release a hydrogen atom.
October 10, 2014

chem
(v1/T1) = (v2/T2) Don't forget to use T in kelvin.
October 10, 2014

Chemistry URGENT!!
The smallest anion probably is H^-. I'm not sure you can say what the largest anion (or cation) is since complex ions can carry a - or + charge and these can get large. It would be complicated to even try to calculate the diameter of those things. For example Fe(CN)63- or ...
October 10, 2014

chem
There is a short way and a long way to do this. Here is the long way. Use PV = nRT and solve for n = mols H2 gas in the 50.0L container. You don't have a T listed so make up one and use it throughout the problem. Use PV = nRT and solve for n = mols O2 in the 25.0 L ...
October 10, 2014

Chemistry
Probably H^+. That's just a bare proton while the other elements have electron shells. Even He^2+ should larger than a H^+.
October 10, 2014

Chemistry
HClO4 + NaOH ==> NaClO4 + H2O mols HClO4 = M x L = ? Using the coefficients in the balanced equation (they are 1:1), convert mols HClO4 to mols NaOH. Now M NaOH = mols/L. You know mols and L, solve for M
October 10, 2014

Conversion again (3 question finish-up)
You may want fractions because you thought you had a sure fire way to work these problems on your last post. I have posted a response there since your 0.114 fraction IS equal to 57/500 but 57/500 is NOT the fraction for the problem of 10 ft/min to mph.
October 10, 2014

Conversion again (3 question finish-up)
You need to learn how to do the conversions. I'll show you how to do the first one. You want to convert m/min to km/sec Let's work on the m to km first. There are 1000 m in a km. That 1000 m/km is a conversion factor. Therefore, 0.85 m x factor = km. Now plug in the ...
October 10, 2014

chemistry
mols C2H5OH = grams/molar mass. Use density to convert mL to grams. mols H2O = grams/molar mass. Use density to convert mL to grams. Then XC2H5OH = nC2H5OH/total mols XH2O = nH2O/total mols pH2O = XH2O x PoH2O,/sub> pC2H5OH = XC2H5OH x PoC2H5OH Ptotal = pC2H5OH + pH2O
October 10, 2014

Chemistry
2C2H2 + 5O2 --> 4CO2 + 2H2O I assume the T is constant. Use PV = nRT. Plug in P = 145 atm V = 7.00 L N = ? R = 0.08206 T = not given but I would use any convenient number, say 300. Solve for n of O2. Use n and the equation to convert to mols C2H2, plug that n back into PV...
October 10, 2014

chem 12
The answer isn't 18 g/s; it's 18 g/10 seconds and problem asked for grams in 10 seconds.
October 10, 2014

chem 12
0.75 mols/min x(1 min/60 s) x 10 s = approx 0.12 mols C12H22O11 in 10 s. You get 12 times that C so you have 0.12 x 12 = approx 1.5 mol C and that x atomic mass C = grams. Remember those first numbers are approximations so you should recalculate from the beginning.
October 10, 2014

chem 12
See my response above but I don't think the answer is 18 g/s.
October 10, 2014

Conversion
Yes, 0.114 is 57/500 but 57/500 is not the right fraction. The answer really is 0.1136364 which rounds to 0.114 mi/hr. I don't know how you arrived at 57/500. The lowest fraction is 15/132.
October 10, 2014

College chemistry
mols Cl^- = M x L = ? Using the coefficients in the balanced equation, convert mols Cl^- to mols Cr2O7^2- and that is mols Cl^- x 1/6 = ? The M Cr2O7^2- = mols/L. You know M and mols, solve for L and convert to mL.
October 10, 2014

Chemistry
C3H8 + 5O2 ==> 3CO2 + 4H2O dHrxn = (n*dHf products) - (n*dhf reactants) Then convert dHrxn from 44g (1 mol in the equation above) to 19.0g. ? = dHrxn x 19.0/44 If you carry the sign over from the first calculation you will get the correct sign for the smaller amount.
October 10, 2014

Chemistry
H should be H2. FeClO4 should be Fe(ClO4)2 Fe + 2HClO4 ==> Fe(ClO4)2 + H2 This equation you wrote is balanced but the predominate product isn't Fe(ClO4)3. 2Fe(s) + 6HClO4 (aq) --> 3H2 (g) + 2Fe(ClO4)3
October 10, 2014

chemistry
heat lost in melting ice + heat gained by H2O from melted ice + heat lost by water @ 25C = 0 heat lost by melted ice = mass x heat fusion = 15 x heat fusion. heat gained by H2O from ice = mass x specific heat H2O x (Tfinal-Tintial) = 15 x specific heat H2O x (Tfinal-0) heat ...
October 10, 2014

chemistry
In round numbers the pH is 5.0. You dilute the base along with the acid and by the same amount; therefore, the ratio of base to acid stays the same and the pH doesn't change. Dilution has no effect on the pH of a buffer but of course we all know that has limitations.
October 10, 2014

Chemistry
So c = f*w. f = frequency in Hz w = wavelength in m c is speed of light in m/s
October 10, 2014

Chemistry
See your post above.
October 10, 2014

chemistry
mols = grams/atomic mass Al.
October 10, 2014

Chemistry
https://www.google.com/search?q=calorimeter+pictgure&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb
October 9, 2014

chemistry
mols Mg from MgBr2 = M x L = ? mols Mg from Mg(Ac)2 = M x L (Mg) in final solution = total mols Mg/total L solution.
October 9, 2014

chemistry
I don't think so.
October 9, 2014

Pharmacy Tech
(15 g/2000 mL) x 100 = ?%w/v and this assumes the solution is 2000 mL and not more than that. Technically I can't do this calculation unless you gave a density.
October 9, 2014

Chemistry
NaOH + HA --> NaA + H2O mols NaOH = M x L = ? mols HA = same since the ratio of acid to base is 1:1 (look at the coefficients) mols HA = grams/molecular weight. You know mols HA and grams HA, solve for molecular weight.
October 9, 2014

Chemistry
The pH of the solution will be determined essentially by the formic acid because it is the stronger of the two. I would do an ICE chart for HCOOH and solve for H^+, then convert to pH.
October 9, 2014

chemistry
mols KOH = grams/molar mass = ? mols HCl = M x L Which is in excess. How much is the excess. If H in excess, (H^+) = mols/L solution. If OH in excess, ((OH^-) = mols/L. Then pH = -log(H^+) if H^+ is in excess. If OH is in excess it is pOH = -log(OH^-), the pH + pOH = pKw = 14...
October 9, 2014

chem
You didn't give an equation.
October 9, 2014

chemistry
2HNO3 + Ca(OH)2 ==> Ca(NO3)2 + 2H2O mols Ca(OH)2 = M x L = ? Convert mols Ca(OH)2 to mols HNO3 using the coefficients in the balanced equation. M HNO3 = mols HNO3/L HNO3
October 9, 2014

Chemistry
I don't see a pressure or a density. Use PV = nRT assuming you have a pressure somewhere and solve for = number of mols. Then find the density of liquid N2 at that temperature (I don't know what K| stands for) and use volume = mass/density.
October 9, 2014

Chem 2
mols urea = grams/molar mass mols H2O = grams/molar mass Xurea = nurea/total mols from above. XH2O = nH2O/total mols. PH2O = Xurea*PoH2O Lowering is Plowering = XH2O*PoH2O
October 9, 2014

Chemistry
Use the HH equation. pH = 4.80 pKa = 4.74 Solve for the ratio of (base)/(acid). That is equation 1. The second equation is (base) + (acid) = 0.15 Solve these two equations for (base) and (acid), then convert to mL by using the dilution formula of mL1 x M1 = mL2 x M2 mL1 x 1M ...
October 8, 2014

Organic Chemistry
You've said it funny. Do you mean it is 0.1g benzoic acid + 0.1 of X and 0.1 g of Y? If so then mols = g/molar mass = 0.1g/molar mass benzoic acid which is about 122. If that isn't what you meant and the mass benzoic acid is 0.3 g, then 0.3/122 = mols benzoic acid.
October 8, 2014

incomplete---chemistry

October 8, 2014

Chem Help Please!
mols NaOH needed = M x L = ? Then grams = mols x molar mass = ? Weigh out the NaOH, add to a volumetric flask, add some water, swirl to dissolve all of the solid, make to the mark of the flask, mix thoroughly. Same for HCl.
October 8, 2014

Chemistry
mols = grams/molar mass
October 8, 2014

chemistry
There are 6.02E23 molecules in 1 mol so there are 0.07 x 6.02E23 molecules in 0.07 mols. Since there are 5 O atoms in 1 molecule of N2O5, # O atoms will be 5x the number of molecules N2O5.
October 8, 2014

Chem
2K + Br2 ==> 2KBr mols K = 2/atomic mass K = about 0.05 mols Br2 = 2/molar mass Br2 = about 0.012 Convert mols K to mols Br2. That's about 0.05 x (1 mol Br2/2 mols K) = about 0.05 x 1/2 = about 0.025. Do you have that many mols Br2? NO, so Br2 is the limiting reagent.
October 8, 2014

o-chem
ethyl 4-aminobenzoate is an ester. The NaOH cleaves the ester and forms CH3CH2OH and the sodium salt of 4-aminobenzoic acid. Then the addition of HCl replaces the Na^+ with a H^+ to form the 4-aminobenzoic acid
October 8, 2014

Chemistry
There are some rather large molecules that have something other than C. Si, for example.
October 8, 2014

Chemistry
C, H, and O atoms hooked together in different numbers and in different arrangements.
October 8, 2014

Chemisty
Right so far. Find mols Ag2S, convert to mols NaNO3, convert to g NaNO3 and stick in the % formula. %NaNO3 = (mass NaNO3/mass sample)*100 = ?
October 8, 2014

Chemistry
mols NO3^- in KNO3 = M x L = ? mols NO3^- in Mg(NO3)2 = 2*M x L = ? M NO3^- = total mols/total L solution
October 8, 2014

chemistry
mols K3Fe(CN)6 = M x L = 1E-3M x 0.100 L = ? Then grams = mols x molar mass = 1E-4 x 329.24 = 0.032924 g The NaNO3 provides only the 100 mL volume. In the end you will have a solution that is 1E-3 M in KeFe(CN)6 and also 0.2 M in NaNO3
October 8, 2014

Chemistry
The N-H stretching is not there in the dimethyl compound because the H atoms are missing on the -NH2 portion.
October 8, 2014

Chemistry
The general gas law is PV = nRT. n = grams/molar mass which makes this come out to be PV = gRT/M and this can be rearranged to P = gRT/MV where M is molar mass or P*M = gRT. Substitute and solve for M = molar mass. I get about 21 but you need a more accurate number than that ...
October 8, 2014

Chemistry
2Ag2O ==> 4Ag + O2 PV = nRT Ptotal = pO2 + pH2O 760 = pO2 + 26.7 pO2 = 760-26.7 and convert to atm. Solve for n = mols O2 and don't forget to convert T to kelvin. Then ? mols O2 x (2 mols Ag2O/1 mol O2) = ? mols O2 x 2/1 = ?? Ag2O Convert mols Ag2O to grams. g = mols x ...
October 8, 2014

Chem Help Please!
If the specific rotation of R is +35 then the rotation of S must be -35.
October 8, 2014

Chemistry
H2CO3 = carbonic acid NaOH = sodium hydroxide H2CO3 + 2NaOH ==> Na2CO3 + 2H2O
October 8, 2014

Chemistry
H atoms in water = 2*1.60E25 H atoms in NH3 = 3*8.50E24 Total = ?
October 8, 2014

chemistry
You could have weighed the Cu or CuO wrong. Weighing Cu wrong changes mols Cu and weighing CuO wrong changes mols O since you used the difference between Cu mass and CuO mass. The Cu you used may have had an oxide coating on it so you didn't have a true weight of Cu. You ...
October 7, 2014

chemistry
Well, you could just take a look at the numbers and see that 0.114 to 0.116 is for all practical purposes 1:1 so you would write CuO. But if you don't see that, an often you can't because the numbers don't come out that well, what you do is divide the smallest ...
October 7, 2014

chemistry
There is 1 atom Cu in 1 molecule of CuSO4.H2O; therefore, 0.114 mol CuSO4.H2O must contain 0.114 mols Cu. It also contains 0.114 mols S, 5*0.114 mols O [that's 4*0.114 from CuSO4 and another 0.114 from the O of H2O] and 0.114 mols H2O (and that can be broken down to 2*0....
October 7, 2014

Chemistry
Is this part of the same question? If so you must have some of A, some of B and some of C Mix A with the three. It will not react with A^- but will with B^- and C^- Mix B with the three. It will not react with A or B or C. Mix C with the three and it will not react with A but ...
October 7, 2014

chemistry
density = mass/volume mass = 17.62 g. volume = 36.1 mL - 29.9 mL = ? Substitute and solve for density.
October 7, 2014

chemistry 112
mols H2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. Then M NaOH = mols NaOH/L NaOH
October 7, 2014

Chemistry
I found this and it has A,B,and C in it but the two questions don't seem to be the same nor do they have any obvious connection. http://www.jiskha.com/display.cgi?id=1412727782
October 7, 2014

Chemistry
You must have more information than that but I can't find the other post.
October 7, 2014

Chemistry
5O2 + 2N2 ==> 2N2O5 mols O2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols O2 to mols N2O5 Now convert mols N2O5 to grams with g = mols x molar mass = ?
October 7, 2014

chemistry
mols = g/molar mass. You know molar mass and mols, solve for grams.
October 7, 2014

Chemistry
NaOH + KHP ==> NaKP + H2O Note that 1 mol NaOH = 1 mol KPH. mols KHP = grams/molar mass mols NaOH = mols KHP. M NaOH = mols NaOH/L NaOH. You now mols and L, solve for M
October 7, 2014

Chemistry
Calculate mols H^+ from the acids and mols OH^- from the bases. Total H^+ and total OH^- and you'll know which is the larger. Subtract one from the other to see which is in excess and by how much.
October 7, 2014

Chemistry
C + B^- ==> C^- + B You know B^- us colorless and it turns yellow which is the color of B. So the reaction is as I wrote above. C gains electrons in going to C^- so it is reduced. B^- loses electrons in going to B. It is oxidized. C+ A^- ==> stays red which means no ...
October 7, 2014

CHEMISTRY
Wouldn't you think less than?
October 7, 2014

chemistery
2NaOH + H2SO4 ==> 2H2O + Na2SO4 mols NaOH = grams/molar mass = 0.644/40 = approx 0.016 but you need a better answer than this estimate. mols H2SO4 = 1/2 mols NaOH (Look at the coefficients in the equation)= 0.008. M H2SO4 = mols/L. You know mols and you know L, solve for M...
October 7, 2014

Chemistry
A chemical change occurred. A gas was released and not all of the compound decomposed. It was a compound since a gas was evolved and that wasn't all of the material.
October 7, 2014

College chem
mols P = 0.142/31 = 0.0046 approx mols F = 0.436/19 = 0.023 Now find the radio of these to each other with the smallest being no less than 1.00. The easy way to do that is divide the smallest number by itself then divide the other number by the same small numer.
October 7, 2014

Chemistry
(V1/T1) = (V2/T2)
October 7, 2014

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