Monday
May 4, 2015

Posts by drbob222


Total # Posts: 48,680

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

no data to explain---chemistry

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

chemistry
How many mols do you need? That's M x L = mols. Then mols = grams/molar mass. You have mols and molar mass, solve for grams.
April 30, 2015

chemistry
1 mol A ==> 1 mol B grams A = determined from density. mass = volume x density = 10 mL x 0.75 g/mL = 7.5 g. mols A = grams/molar mass = ? Since the reaction is 1 mol A to 1 mol B, then mols B = mols A Grams B = mols B x molar mass B = ?g theoretical yield (TY). The actual ...
April 30, 2015

Chemistry-is this right?
Thanks for letting me know.
April 30, 2015

chemistry
OK. My guess is that "theoretical pH) means to calculate what you think it should be based on the dilution of the original 0.1 M solutions. In that case you go with the 0.1 M HCl x (1/10) = 0.01 M HCl for HCl and theoretical pH of 2 and 0.1 M NaOH x (1/10) = 0.01 M NaOH ...
April 30, 2015

chemistry
You didn't have any of that information in the first post and I'm not sure I understand what you want now. However, if you took 1 drop of 0.1 M HCl and diluted it with 9 drops of DI water the concn of HCl in the diluted solution is 0.1 M HCl x (1 drop/10 drops total...
April 30, 2015

chemistry
I've responded to this also. If you can't find it I'll look and send you a link.
April 30, 2015

Chemistry
mols NaOH = M x L = ? mols acetic acid = mols NaOH since the reaction is 1 mol acetic acid = 1 mol NaOH. Then M acetic acid = mols acetic acid/L acetic acid.
April 30, 2015

Chemistry
I work these limiting reagent (LR) problems the long way. mols CH3COOH = M x L = ? mols NaHCO3 = M x L = ? Using the coefficients in the balanced equation, convert mols CH3COOH to mols CO2. Do the same and convert mols NaHCO3 to mols CO2. It is likely these two numbers will ...
April 30, 2015

chemistry
This looks ok to me; I assume you've seen my earlier response.
April 30, 2015

Science/Conversion
You don't have conversions here. You may ask how to convert 10 ug/mL to ng/uL but you already have the ng/uL filled in. Are we to check to see if this is correct?
April 30, 2015

chemistry
You know you get 802.3 kJ for burning 16 g CH4 and you know that from the question. All you need to do is to convert that to (it's just a proportion) to 237 and not 16 g CH4. heat produced is 802.3 kJ x (237/16) = ?
April 29, 2015

chemistry
And it's still wrong. Look at my earlier response. I told you EXACTLY how to do it. You only need to that equation I wrote and change the 0.139 to 0.129 and punch in the numbers.
April 29, 2015

chemistryH
Your net ionic equation is correct. Good work. However, I think the problem is a little misleading since the net ionic equation doesn't have a conjugate base for the acid. If you write H^+ + CO3^2- ==> HCO3^- as the net ionic equation, which I believe is correct, then ...
April 29, 2015

chemistry
And I think it is wrong. q = mass Pb x specific heat Pb x (Tfinal-Tinitial) = 225 x 0.139 x 20 = ?
April 29, 2015

chemistry
I have some serious problems with this equation. Is this the equation you were given; i.e., were you given the products?
April 29, 2015

Chemistry
Frankly, I don't think it is a very good buffer; however, small amounts of OH will be neutralized by the H3O^+ but I wouldn't bank on it.
April 29, 2015

Chemistry
#1. How many mols NaCl do you want? That's mols = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams. To prepare the solution you place that many grams (the ? calculated above) in a 250 mL volumetric flask, add some water, swirl until all...
April 29, 2015

Chemistry-is this right?
No. You must be pushing a wrong button. Hit the 10^x button, then -4.9 and read 1.256E-5M for H3O^+ For the second part, then pOH = 14- pH = 9.1 (NOT OH = 14-pH) then OH = 10^-pOH OH = 7.94E-10
April 29, 2015

Chemistry
I beg your pardon. PV = nRT DOES work. That provides at least some information to answer the second part. I didn't answer the second part. Frankly I think the second part is a guess since we don't know how strong the can is; however, I would hazard a guess that at ...
April 29, 2015

Chemistry
Use PV = nRT n = grams/molar mass. Calculate P. For the others, read this. http://en.wikipedia.org/wiki/Intermolecular_force
April 29, 2015

Chemistry
1. The original chemical has been changed to something different. 2C6H8O6 + O2 ==> 2C6H6O6 + 2H2O mols vit C = grams/molar mass = 1g/molar mass = ? Using the coefficients in the balanced equation, convert mols vit C to mols to mols O2. Convert 1.00 g O2 to mols. mols = 1.00...
April 29, 2015

Chemistryh
1. pH = -log(HCl) = -log 0.1 = 1 2. pOH = -log(NaOH) = -log(0.1) = 1 The pOH + pH = 14; pH = 14-pOH = 14-1 = 13
April 29, 2015

Chemistry
Is this just to keep me busy? What do you not understand about this? Remember -dH is exothermic. Large Keq means the reaction is favorable; small K means not very favorable. Le Chatelier's Principle says when a system at equilibrium is disturbed, it will shift so as to ...
April 29, 2015

Chemistry
Use the Henderson-Hasselbalch equation which I think is the same answer I wrote about 12 hours ago.
April 29, 2015

chem
I never heard of this. Obviously there be a beginning. A phase where the forward and reverse directions are adjusting themselves with respect to one another. When equilibrium is established you have the final stage. I have no idea if this is what you want or not but these what...
April 29, 2015

Chemistry
Very good. Go to the top of the class.
April 29, 2015

Chemistry
a is not right. 6 mols NH3 x (2 mols O2/2 mol NH3) = 6 mols O2. b. just half that since a is 2x too high. c and d are ok.
April 29, 2015

science
I would think a dead tree was already decomposed (at least parts of it are decomposed) so this organism must be a scavenger.
April 29, 2015

chemistry
All of that looks ok to me.
April 29, 2015

chemistry
I would not round from 1.82 for pH of 0.015 M HCl. In logarithms the 1 of 1.82 just tells you the location of the decimal point in the 0.015 number so that counts as only two significant figures in 1.82 you can get OH either of two ways. pH + pOH = 14 and after you know pH you...
April 29, 2015

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