Friday
May 22, 2015

Posts by DrBob222


Total # Posts: 49,010

chemistry
I think you are on the right track. You just have another step or two to go. And you're right, this is a limiting reagent problem; I usually work these the long way. mols Pb(NO3)2 = M x L = approx 0.00121 mols Na2SO4 = approx 0.00130 Pb(NO3)2 x Na2SO4 ==> PbSO4 + 2NaNO3...
May 6, 2015

Chemistry
mols HCl = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols HCl to mols CaCl2. Now convert mols CaCl2 to grams CaCl2. g = mols x molar mass
May 6, 2015

chemistry
I presume you have [H2CO3] and [H2O^+]. You can use [H3O^+]{OH^-] = Kw = 1E-14 to solve for (OH^-). (HCO3^-) = essentially the same as (H3O^+) (CO3^2-) = Ka2
May 6, 2015

chemistry
I don't believe the answer by anonymous will get it. Use P1V1 = P2V2 226 x 1.7 = 2.7V2. Solve for V2.
May 6, 2015

chemistry
The following determines the M and N. If you really want molality repost but m = mols/kg solvent and probably you can do that yourself. 1.10 g/mL x 1000 mL x 0.15 x (1/98) = ?M Technically one cannot determine the N without knowing the reaction; however, USUALLY, it is M*#H ...
May 6, 2015

Chemistry
Why didn't you show what you had? But thanks for telling us your next problem. How many mols vit C do you have. That's 1/molar mass = ? and I'll make up a number say 0.1 but of course you know that isn't right. Then you can convert mols of vit C to mols of ...
May 6, 2015

Chemistry
mols urea = grams/molar mass = ? mols H2O = grams/molar mass = ? Total mols = sum mol fraction = XH2O = mos H2O/total mols pH2O = XH2O*PoH2O. If you want it at 25 C, use Po at 25 C.
May 6, 2015

Chemistry
I would do this. pHe + pH2O = 1.16 atm. Calculate pHe alone but be careful that you use the same units. Then use PV = nRT and solve for V for the dry He. Using that number for n dry He, solve PV = nRT for n for H2O at 17.5 torr. Add n H2O + n He for total mols, then PV = nRT ...
May 5, 2015

chemistry
I'm sure I worked this earlier. Let me know if there is something you don't understand about the process.
May 5, 2015

chemistry
pKa = -log Ka or Ka = 10^-pKa. Solve for Ka.
May 5, 2015

Chemistry
I assume the heat capacity of the calorimeter is zero. heat lost by metal + heat gained by waer = 0 [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0. Substitute and solve for specific heat metal.
May 5, 2015

Chemistry
My assumption is that you are to use bar as the standard pressure and not atm. If you want atm change bar to atm and recalculate accordingly. 2NaHCO3(s) ==> Na2CO3(s) + H2O(g) + CO2(g) a. Ptotal = 7.68 bar = pH2O + pCO2 pH2O = pCO2 = 7.68/2 = ?bar b. Substitute the pH2O and...
May 5, 2015

Chemistry
You need to re-write the equations as such. PbI2(s) ==> Pb^2+ + 2I^- Pb^2+ + 4I^- --> [PbI4]^2- -------------------------- add the two equation to get this. PbI2(s) + 2I^- ==? [PbI4]^2- for which Keq = Ksp*Kf You can plug in Ksp and Kf and see that Keq is what it should ...
May 5, 2015

chemistry 121
...........HOAc + H2O ==> H3O^+ + OAc^- I..........0.5M............0.......0 C..........-x..............x.......x E.........0.5-x............x.......x Substitute the E line into Ka expression and solve for x = (H3O^+) then convert to pH. If you know Ka (and you do) then ...
May 5, 2015

Equilibrium constant
..........SO2Cl2 ==> SO2 + Cl2 I.........0.022......0......0 C.........-x.........x......x E.......0.022-x......x......x The problems tell you that (Cl2) = x = 1.7E-2. Substitute into Kc expression and calculate Kc
May 5, 2015

Equilibrium
Keq = (I)^2/(I2) = 0.015 You know I2 at equilibrium and you know keq, solve for I.
May 5, 2015

chemistry
volume to start = 2.29 volume added = 15.75 total volume = ? 0.723M x (2.29/total volume) = ? Note: This assumes volumes are additive; technically they are not but in dilute solutions like this the are for all practical purposes (still not technically)
May 5, 2015

chemistry
Would you believe I have no idea what IL-23 power is (although I assume you mean powder). Let's see. If I had 10 ug/0.1 mL wouldn't that be 100 ug/mL
May 5, 2015

chemistry
We're still giving you freebies. Somewhere down the line you need to start telling us what you think and why or at least tell us what you don't understand about the problem. CH4 + 2O2 ==> CO2 + 2H2O The problem isn't clear about which gases to separate. I assume...
May 5, 2015

chemistry
PV = nRT If you use kPa for P, use 8.314 for R. Remember T must be in kelvin.
May 5, 2015

chemistry
Responded above. Good luck on the exam.
May 5, 2015

chemistry
right. Note that Cu is below hydrogen in the activity series; therefore, it will not displace hydrogen from the acid. What you get is an oxidiation/reduction reaction in which the Cu is oxidized to Cu^2+ and the H2SO4 is reduced to SO2. But that only happens if the H2SO4 is ...
May 5, 2015

chemistry
I have news for you. Copper will not dissolve in H2SO4 unless it is heated. If heated it will react but it does not produce H2 gas. It produces SO2. So which equation is right?
May 5, 2015

science
specific heat has units of J/g*K or joules/gram/degree kelvin. Typically, specific heat is the heat required to raise the temperature of 1 gram of some material by 1 degree K. Heat capacity has units of J/K; i.e., note no "specificity" in amount as in grams. There is...
May 5, 2015

chemistry
It is a unit like a loaf of bread(so many slices), a dozen eggs (12 of anything), a gross of pencils(144 of anything), a ream of paper(500 sheets). A mole is 6.022E23 of anything.
May 5, 2015

chemistry
1. Write and balance the equation. 2Al + 6HCl ==> 2AlCl3 + 3H2 2. Convert 5.8 g Al to mols. mol = grams/atomic mass = 5.8/27 = approx 0.2 but you need a more accurate answer than that estimate. 3. Using the coefficients in the balanced equation, convert mols Al to mols HCl...
May 5, 2015

chemistry
0.997 g/mL x 500 mL x (1 kg/1000 g) = ?
May 4, 2015

Chemistry Help - Check Please
That sounds good to me although I'm not an organic chemist.
May 4, 2015

Chemistry help
It would help if you told us what you don't understand about these. For #1, pH = -log(H^+). Substitute and solve for pH. For #2. Same formula. I assume this is the TOTAL H^+ and there is no need to add in any contribution due to the ionization of H2O.
May 4, 2015

Chemistry
mols AlCl3 = grams/molar mass. You know molar mass and grams, solve for mols. Then m = molality = mols/kg solvent. You know kg solvent and mols, solve for m. Then delta T = i*Kf*m You know Kf and m; i for AlCl3 is 4. Solve for delta T. Then subtract delta T from the normal ...
May 4, 2015

Science
f = ma f is same mass greater a must be
May 4, 2015

chemistry
Is that m or M? I assume you know there is a difference but since you don't use the caps key we never know.
May 4, 2015

CHEMISTRY
(V1/T1) = (V2/T2) Remember T must be in kelvin.
May 4, 2015

Chemistry
96,485 coulombs will form approx 87/2 = approx 44 g MnO2. These are estimates and you need to redo them with more accurate numbers. How many coulombs do you need to produce 1000 g? That's approx 96,485 x (44/1000) = ? = Q Then Q = amperes x seconds. Substitute and solve ...
May 4, 2015

Chemistry
Ecell = Eocell - (0.05916/n)*log(dilute/concd) Eocell = 0 Substitute and solve for Ecell.
May 4, 2015

Chemistry
What values are you using for Ered.
May 4, 2015

science
KE = 1/2*m*v^2 If v is 2x as much then KE is 4x as much.
May 4, 2015

Chemistry
It would have helped if you had shown you work. I get K = 1.36 and your equation looks ok to me. Anything else that might shed some light on the problem? The only possibility I have is that you and I may not be using the same E value.
May 4, 2015

Chemistry
What are you using for the Ered Sn and Pb? Do you have any concentrations given or are you to assume 1 M concns?
May 4, 2015

chemistry
1 orange costs $1.00; what's the cost of 2 oranges? 1 mol occupies 22.4 L; what's the volume occupied by 2 mols?
May 4, 2015

Chemistry
You have the wrong formula and wrong data. Hf is heat fusion; you want Hvap. Hf is 80 cal/g; Hvap is 540 cal/g Q = m*Hvap Hvap = 540 cal/g
May 4, 2015

Chemistry
The reaction is exothermic and you know that because the temperature of the water increased. q = 6795 J for 0.85 mol; therefore, q = 6795/0.85 = dH = ? Remember to add a - sign since this is exothermic. Also remember to convert from J to kJ.
May 4, 2015

Chemistry
PV = nRT Make sure P, V, R units are consistent.
May 4, 2015

chemistry
mass = volume x density You know d and m, substitute and solve for v.
May 4, 2015

Science 6 th grade
I passed on this question because 2 and 4 are confusing. I don't think 2 has a correct choice. A can't be right. For B I have no way of knowing the speed of the car next to me. c makes no sense. d might work if I could count the seconds it takes to reach the billboard ...
May 4, 2015

science
How would you like for us to help you on this assignment?
May 4, 2015

science
Post a question is you have one. This is not a site to pass the time of day.
May 4, 2015

Chemistry
http://www.jiskha.com/display.cgi?id=1430350750
May 4, 2015

Stoichiometry
mols SO2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols SO2 to mols H2SO4. Now convert mols H2SO4 to grams. g = mols x molar mass = ? You find the g O2 by the same process. Using the coefficients, convert mols SO2 to mols O2 then convert ...
May 4, 2015

chemistry
Na2CO3 + 2HCl ==> 2NaCl + H2O + CO2 mols Na2CO3 = M x L = ? Using the coefficients in the balanced equation, convert mols Na2CO3 to mols HCl. Then M HCl = mols HCl/L HCl. YOu know M HCl and mols HCl, solve for L HCl.
May 3, 2015

Chemistry(difficult)
I think t is 3.7E9 years according to the problem. Here is what I would do. k = 0.693/t1/2 and solve for k. Then ln(No/N) = kt You know k and t, solve for N/No. If I understand the problem, the current mass U238 is 1.185g. So you know No/N and N, solve for No which is the ...
May 3, 2015

Chemistry
P1V1 = P2V2
May 3, 2015

Chemistry
Look at the equation. If it is forming C2H2 PLUS 227.4 (whatever units that you didn't copy) it is GIVING OFF HEAT so it must be exothermic.
May 3, 2015

Chemistry
You must know the specific heat of the granite. If you have that in your problem then q = mass granite x specific het granite x (Tfinal-Tinitial) q = ? mass boulder = 2966000 specific heat granite = ? you must have this. Tfinal is given Tinitial is given.
May 3, 2015

chemistry
How many mols do you have? That's M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
May 3, 2015

science
68.9 -56.424 ------------ =12.476 but you may not use that many places. In subtraction, you may use as many places to the right of the decimal as the LEAST precise which means the 24 of the .424 number wont count and the answer is 12.5 g. You can read about significant ...
May 3, 2015

chemistry--last time i promise
Since these are 1:1:1:1 you can take a short cut and see that CO is the limiting reagent. So 5 atm CO reacts with 5 atm H2O to form 5 atm CO2 and 5 atm H2 with 3 atm H2O left over. The final P is 16 atm. Your prof may not like this so you can do it conventionally this way. ...
May 3, 2015

Chemistry-Acids
Actually, you don't but if the empirical formula is HCHO2 or CH2O2 and the Lewis structure looks like HCOOH it's a good bet it is formic acid. That's why they write the abbreviated formula as HCHO2 and that USUALLY means the first H written is the one that ionizes ...
May 3, 2015

Chemistry-Acids
HCHO2 probably is formic acid. It might be easier for you to see if it was written as HCOOH. It's the H on the right hand side that is the acidic hydrogen and if you look at it that way you would write HCOOH + H2O => H3O^+ + HCOO^-. Often these are written with that ...
May 3, 2015

Chemistry
Perhaps. Partial pressure is what you are to find and you should understand that partial pressure is NOT measured in degrees C but in atm or mm Hg or some other pressure unit. What you want to do is to convert 1500 lb/in^2 to atm Then use PV = nRT, substitute with the ...
May 3, 2015

chemistry
dG = dH - TdS At the melting point, the process is in equilibrium; therefore, dG is 0 Set dG to zero, you know dH and dS, solve for T.
May 3, 2015

Science
The smaller wire means higher resistance and that causes more heating of the wire to occur. If the wire becomes too hot it can ignite. This can be prevented by using the proper cord to hook the refrigerator to the electrical outlet.
May 3, 2015

Chemistry
I have corrected your equation. CaC2(s)+2H2O(l)-->C2H2(g)+Ca(OH)2(s) mols CaC2 = 84g/molar mass = ? Using the coefficients in the balanced equation, convert mols CaC2 to mols C2H2. Then convert mols C2H2 to volume at the conditions listed using PV = nRT and solve for V in ...
May 3, 2015

Chemistry (Molarity)
The problem asks for concentration and probably that means M or mols/L (or millimols/mL). So you want to find the mols of each ion, divide by total volume and that will be M. I prefer to find millimols and divide by mL. For 48 mL 0.11 M KClO3 you have 48 x 0.11 = 5.28 ...
May 3, 2015

chemistry
(PCl5) = 0.239 mol/2.85L = approx 0.08 but you need a better answer than that estimate. .........PCl5 ==> PCl3 + Cl2 I.......0.08.......0......0 C........-x........x......x E......0.08-x......x......x Substitute the E line into the Kc expression for PCl5 and solve for x and...
May 3, 2015

chemistry
k = 0.693/t1/2 ln(No/N) = kt No = 200 N = 25 k from above Solve for t in years.
May 3, 2015

Dance
high steppers high toppers hi toppers hi steppers hot dance team This should get you started. I'm sure my colleagues will have better suggestions.
May 3, 2015

Chemisty
Following Steve's suggestion, what adding some specificity to it.
May 3, 2015

chemistry
What does AQ mean? Why is it not 4.27 M?
May 3, 2015

Chemistry
What reaction? And you must have some other information. You have two unknowns and only 1 piece of info. You could have a large amount of Ti and a small amount of I2 or the reverse and meet the requirement of 1.38E3 kJ
May 2, 2015

chemistry
https://www.google.com/search?q=lewis+structure+H3AsO4&tbm=isch&imgil=7o_6LvRTF6H2UM%253A%253BFeUn1lwCtnvZSM%253Bhttp%25253A%25252F%25252Fwww.lookchem.com%25252Fcas-777%25252F7778-39-4.html&source=iu&pf=m&fir=7o_6LvRTF6H2UM%253A%252CFeUn1lwCtnvZSM%252C_&usg=...
May 2, 2015

Chemistry
You must have something in your experiment from which you can get the equations. I can guess what you might do but that isn't good enough. I presume you add Ni to HNO3 to dissolve the metal BUT you're not given any grams HNO3 used. Where does the Na2CO3 come in? What ...
May 2, 2015

Chemistry
Do you have the equation(s)? Can you use stoichiometry to calculate the grams NiSO4.6H2O you can produce? Exactly what trouble are you having with this?
May 2, 2015

Chemistry
Why must you use atm? You use atm for gases and when you have pressures, these aren't gases so you use molarity. Calculation of Q occurs for either. In fact, one may use, if the situation occurs, a mix where pressure is used for the gas ad molarities for the solutions. For...
May 2, 2015

Chemistry
I assume this is not at equilibrium. If that is the case, then dG = dGorxn + RTlnQ dGorxn you obtain from dGorxn = *n*dGo formation products) - (n*dGo formation reactants) Then Q is (HI)^2/(H2)(I2)
May 2, 2015

Chemistry
ln*(No/N) = kt No = 20 mg N = ? k from the problem. t = 5 hours. Note: since k is given in per min and you want to know in 5 hours, I recommend you convert 5 hours to minutes.
May 2, 2015

Chemistry
You would do well to keep the same screen name. We can help better if you do that. rate = 1/2*d(NO2)/dT d(NO2) = 450-320 = 130 dT = 20 rate formation O2 is 2x rate NO2 decomposition
May 2, 2015

DrBob222
Use the coefficients as you would for a stoichometry problem. 2C2H6 + 7O2 --> 4CO2 + 6H2O 0.44 x 7/2 = ?
May 2, 2015

physics
Specific heat
May 2, 2015

Chemistry
Are these partial pressures at equilibrium? Perhaps they are not. If not Use dGrxn = dGo + RT*lnQ for Q = p^2H2O/pSO2*p^2H2S
May 1, 2015

Chemistry
Why don't you just change mL to L and change ug to grams. Then d = m/v directly in g/L.
May 1, 2015

chemistry
Isn't that v(rms) = sqrt (3RT/M) M is the molar mass in Kg.
May 1, 2015

chemistry
With gases you may use a shortcut in which L are used directly as mols. L H2 @ STP and 100% yield = 15.5L Cl2 x (2 mols HCl/1 mol Cl2) = 31 L H2O at 100%. At 45% it is 31 x 0.45 = ? L HCl
May 1, 2015

Chemistry
A regular stoichometry problem. See your previous posts OR explain exactly what you don't understand about this and show what work you've done.
May 1, 2015

Chemistry
This is a limiting reagent problem but you start with mols instead of grams. See your previous problem.
May 1, 2015

Chemistry
mass = volume x density Solve for density in g/mL and convert to g/L. OR you can convert mL to L and ug to g first, then divide to obtain g/L directly.
May 1, 2015

Chemistry
See your previous problem. This is not a LR problem BUT in the previous problem you calculated TWO problems like this while this is just one of those problems. The theoretical yield is the mols produced by that one calculation. We'll call that TY. The actual yield (AY) is ...
May 1, 2015

Chemistry
Just follow each step as I wrote them. It will come out. It a horrendous "formula" if you try to write it all at one time. Show what you have done? Where are you stuck? What do you not understand about the next step.
May 1, 2015

Chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. I do these the long way. CaF2 + H2SO4 --> 2HF + CaSO4 mols CaF2 = grams/molar mass = ? mols H2SO4 = grams/molar mass = ? Using the coefficients in the balanced equation, ...
May 1, 2015

Chemistry
mL1 x M1 = mL2 x M2
May 1, 2015

Damon made a typo--Chemistry
I'll show you how to do this the chemistry way. Convert 5.671 g H2O to mols H atoms. That's 5.671 x (2 atomic mass H/molar mass H2O) = approx 0.630 but you need to go through all of these calculations and confirm that. Some I have estimated. Convert 36.933 g CO2 to g C...
May 1, 2015

Chemistry
I agree with 305.3333 L but I would round the answer to 305 L.
May 1, 2015

chemistry
Use PV = nRT and solve for n = total mols mols CH4 = grams/molar mass = ? mols C2H6 = grams/molar mass = ? mols unknown gas = total mols - mols CH4-mols C2H6. mol fraction = XCH4 = mols CH4/total mols. XC2H6 = mols C2H6/total mols Xunknown = mols unkn/total mols pCH4 = XCH4*...
May 1, 2015

chemistry
Assuming the volumes are additive (technically they are not) 0.65 x [250/(250+800)] = ?
May 1, 2015

Chemistry
20*0.300 = x mL*0.150 Solve for x mL = 40 mL Total volume at equivalence point is 40 + 20 = 60 mL HAc + NaOH ==> NaAc + H2O So the solution at the equivalence point is sodium acetate, NaAc, and the concn is millimols/mL = (20*300)/60 mL = ? = approx 0.1 The pH at the ...
May 1, 2015

Chemistry
You may have balanced the equation but it's the wrong equation. Mg + Zn(NO3)2 ==> Mg(NO3)2 + Zn I do these the long way. mols Mg = grams/molar mass = ? mols Zn(NO3)2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Mg to mols of ...
May 1, 2015

Science
Technically, doubters can make a case for all of them being renewable; however, gasoline, natural gas and coal take a very long time (say a million years) so for all practical purposes those are not renewable, certainly not in our life time. Wind is the one that here from day ...
May 1, 2015

Chem
Use PV = nRT n = grams/molar mass CH4
April 30, 2015

Chemistry
You need to convert amu to kg. You can look up the factor on Google. E will come out in joules and you convert that to MeV.
April 30, 2015

chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute and solve for Tf.
April 30, 2015

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