Saturday
December 20, 2014

Posts by DrBob222


Total # Posts: 46,145

chemistry
You know g Ar = 228. Convert to mols, then calculate mols CH4 from mol fraction Ar. XAr = 1.00-0.65 = [mols Ar/(mols Ar + mols CH4)]. Then total KE/mol = 3/2(RT) which allows you to calculate KE for n mols CH4 followed by KE for n mols Ar. Then add those together. (...
October 26, 2014

Chemistry
I'm not sure I have followed the question completely but here is what I think. volume is 5.00 mL and you take 1/5 that or 1.00 mL. The initial 5.00 mL contains 5.00 mL x 1.042 g/mL = 5.20 grams. If you take 1.00 mL of that each mL will contain 5.20/5.00 = 1.042 grams. You ...
October 26, 2014

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O mols Ba(OH)2 = M x L = 0.0186 mols HCl = M x L = 0.0372 These neutralize each other exactly and will produce 0.0372 mol H2O q = mass H2O x specific heat H2O x delta T q = 120 g x 4.184 J/g*C x (26.41-22.19) q = approx 2000 J but you need to ...
October 26, 2014

chemistry
Will you please read this and rephrase it. "contains 1.00 WHAT into 1000 g argon gas"
October 26, 2014

Chemistry
Multiply equation 1 by 2. Add in equation 2. Add in the reverse of equation 3. When you multiply equations multiply dH also. When you reverse an equation, change the sign of dH.
October 26, 2014

Chemistry
See your other post.
October 26, 2014

Chemistry
H3PO4 + NaOH ==> NaH2PO4 + H2O mols NaOH = M x L = ? 1 mol NaOH = 1 mol H3PO4 M H3PO4 = mols H3PO4/L H3PO4.
October 26, 2014

chemistry
(P1V1/T1) = (P2V2/T2) I would make up a convenient number for V1, something like 10 which makes V2 = 10.4. Then substitute and solve for P2. Don't forget T must be in kelvin.
October 26, 2014

chemistry
2.2 g is how many mols propane? That's g/molar mass = 2.2/44 = 0.05 mols. So if 1 mol C3H8 uses 5 mols O2, then ...0.05 mols C3H8 uses x mol O2.
October 26, 2014

chemistry
mols Ca(OH)2 = grams/molar mass. mols OH^- = 2x that M OH^- = mols OH^-/L solution pOH = -log(OH^-) pH + pOH = pKw = 14. After you have pOH you have pKw, solve for pH.
October 26, 2014

chemistry
This is a limiting reagent (LR) problem and we know that because amounts are given for BOTH reactants. C3H8 + 5O2 ==> 3CO2 + 4H2O mols H2O formed if we used 2.5 mol O2 and all of the propane we needed is 2.5 mol O2 x (4 mol H2O/5 mol O2) = 2.5 x 4/5 = 2 mol H2O formed. mols...
October 26, 2014

Chemistry
Re-read my response. Read it completely. Read it carefully. I told you how many mols NO were formed.
October 25, 2014

Chemistry
Here is how you do you it but you will need to go through and recalculate because I will do estimates only. N2 + O2 ==> 2NO Convert mols NH2 to mols NO using the coefficients in the balanced equation. Thats 0.2 mol N2 x (2 mols NO/1 mol N2) = 0.2 x 2/1 = 0.4 Do the same ...
October 25, 2014

chEMISTRY
mols = M x L = ?
October 25, 2014

Chemistry-Help Dr. Bob
That looks ok to me.
October 25, 2014

Science
It appears tp me ou have done it right. You do not add the mass of the solid to the water. You solved for q and got delta H/mol by dividing by the mols of the solid. The only thing left, I think, is to convert J/mol to kJ/mol since that is the usual way of calculating it but ...
October 25, 2014

Chemistry
To be spontaneous dG must be - (that's negative).
October 25, 2014

Chemistry
I think you problem is the molar mass of BiCl3. I think that is 315.34 The rest of it looks ok, at least at first glance.
October 25, 2014

Science HELP!
I agree.
October 25, 2014

chem
I follow some of what you did but not all of it and I don't get the same answer you did. Why not use dE = 2.180E-18J(1/4-1/9) Then lambda = hc/dE For dE I have about 3.03E-19J and wavelength = about 6.56E-7 m or 656 nm or 6560 angstroms which is red.
October 25, 2014

Chemistry
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin.
October 25, 2014

Chemistry
24.6 grams HAc? What's the density of the solution. We need to convert grams to volume. And what are you reacting the HAc with to produce CO2?
October 25, 2014

chemistry
You should type the entire problem here. Since your three posts are together I assume you want to react the acetic adcid with NaHCO3 but I'm guessing. NaHCO3 + HC2H3O2 ==> NaC2H3O2 + H2O + CO2 mols HC2H3O2 = M x L = ? Convert mols HC2H3O2 to mols CO2 using the ...
October 25, 2014

chemistry
Acetic acid is HC2H3O2 OR CH3COOH or HAc. NaHCO3 + HAc ==> NaAc + H2O + CO2 mols CO2 gas in 0.25L is 0.25L x (1 mol/22.5L) = approx 0.0112 Using the coefficients in the balanced equation, convert mols CO2 to mols NaHCO3. That's 0.0112 mols CO2 x (1 mol NaHCO3/1 mol CO2...
October 25, 2014

Chem
No. v = c/lambda is right and 3E8/7.30E-7 is right but you must have punched in the wrong numbers because the answer is not 2.19E14. I obtained 4.11E14/Hz You didn't need to calculate C. You know that;s 3E8 m/s Likewise, you didn't need to calculate lambda. That's ...
October 25, 2014

Chemistry
2C2H6 + 7O2 ==> 4CO2 + 6H2O How many mols ethane do you have? That's 4.42g/molar mass ethane = approx 0.15 but you need a more accurate answer. Then you know you get 1560 kJ for 1 mol so you will get ? for 0.15 mol?
October 25, 2014

Chemistry
B has 5 electrons total and three outside electrons so it is .B. . You note that the three electrons, all unpaired, leaves that fourth spot (at the top)open so one F shares the electron to the left spot, another to the right spot, another to the bottom spot, and the top spot ...
October 25, 2014

chemistry lab
I assume this is the synthesis of aspirin but with no procedure I can't help.
October 25, 2014

Chemistry
How much magnesium chloride. 1 mol Mg is in 1 mol MgCl2 so figure how many mols MgCl2 you have.
October 25, 2014

chemistry
Here is a good lesson in chemistry and you need to learn it and put it practice today. Find the caps key and know when to use it. You certainly need it to start sentences as in the What above. You do NOT need it when you intend to write molality. The small m stands for ...
October 25, 2014

chemistry
C6H12O6 ==> 2C2H5OH + 2CO2 (not balanced) 8 mols fructose should give 16 mols ethanol and that x 46 = 736 g ethanol for the theoretical yield. Technically, I think the yield is 320 g. You may be looking for the percent yield is (320/736)*100 = ?
October 25, 2014

Chemistry
A. mols Mg = grams/molar mass = aprox 0.0082 but you need to redo all of these since I've estimated. B. mols Cl2 = grams/molar mass BUT mols Cl ion is grams/atomic mass or approx 0.0028 C. 0.0082/0.0028 = 2.93 D. 0.0028/0.0028 = 1.00 E. D is rounded to 1.00; C is rounded ...
October 25, 2014

Chemistry
If you have trouble adjusting for the conditions you can use PV = nRT. Plug in n from Steve's work, along with the other conditions, and solve for V in L. Same answer either way but I think this way is a little easier for students.
October 25, 2014

AP Chemistry
For the water: (mass H2O x specific heat H2O x (Tfinal-Tinitial) You have mass, sp.h., Tf and Ti. Substitute and solve for q. Use 4.184 J/g*C for sp.h. H2O For the vessel: There are several kinds of stainless steel. You can look it up on the web and I found several, minimum ...
October 24, 2014

Last BrainMath :(
By the time you posted this you could be through the counting.
October 24, 2014

BrainMath
Neither. 2(S+4) = 16 2S + 8 = 16 2S = 8 S = 4 is how old the sister is now. Next year, what the problem asked, sister will be 5.
October 24, 2014

BrainMath
H is Hector's age = 12 S is sister's age. in 4 yrs H will be 16 in 4 yrs S will be S+4 2(S+4) = 16 S =? Next yrs S will be ?+1
October 24, 2014

Chemistry
k = 0.693/t1/2 Substitute into the below equation. ln(No/N) = kt No = 2 g from the problem. N = to be calculated (how much is left) k from above. t = 10.8 years. Solve for N
October 24, 2014

BRAINMATH
I agree with Writeacher. X is the number, then twice that number is 2x and that less 2 is 2X-2 = 50 X = 26.
October 24, 2014

Chemistry
You are right, equation is balanced so step 1 is ok. Step 2 is not right. If 22,400mL is occupied by 1 mol and you have 45 mL, then 45 mL x (1 mol/22,400 mL) = ? mols. Then proceed to step 3. You have strung steps 2,3,and 4 together which saves time and space but often ...
October 24, 2014

Chemistry
Step 1. Write and balance the equation. MnCl2 + H2SO4 => MnSO4 + 2HCl Step 2. 1 mol occupies 22,400 mL at STP. So how many mols is 45 mL? Step 3. Using the coefficients in the balanced equation, convert mols HCl to mols MnCl2. Step 4. Convert mols MnCl2 to grams. grams = ...
October 24, 2014

Physical Science
Look up the melting point of Pb and the boiling point of Pb. Then T < melting point it is solid. T = m.p. equilibrium between liquid and solid. T > m.p. but < b.p. is liquid T > b.p. is vapor
October 24, 2014

Chemistry
I don't know what you mean by the outer shell of pennies but in 3.2oE22 atom of Cu there are mols Cu = 3.20E22/6.02E23 = ? Then g = mols Cu x atomic mass Cu = ?
October 24, 2014

Chemistry
I presume reaction A is NaOH(s) + H2O ==> Na^+(aq) + OH^-(aq) But don't I need the volume of the solvent and it's identity(specific heat)?
October 24, 2014

chemistry
(mass O/total mass)*100 = ?
October 24, 2014

chemistry
The same as what buffer solution.
October 24, 2014

chemistry
First, balance the equation. It isn't balanced now. mols Ca3(PO4)2 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols Ca3(PO4)2 to mols H3PO4.
October 24, 2014

Chemistry
mols Al2(SO4)3 = grams/molar mass = ? Then M = mols/L solution.
October 24, 2014

chemistry
mols Fe = grams Fe/atomic mass Fe. mols hemoglobin = 1/4 that since there are 4 atoms/molecule mols hemoglobin = grams/molar mass. You know grams ad mols, solve for molar mass. I get something like 65,000 give or take a little.
October 24, 2014

chemistry
1 mol contains 6.02E23 atoms so 2.5 mols will .....
October 24, 2014

Chemistry
1 mol is 6.02E23 molecules so you have 1.20E25/6.02E23 = ? mols.
October 23, 2014

chemistry
This site doesn't handle spaces very well. I assume you mean 0.4 L of 0.025M H2SO4 with 0.4 L of 0.030M NaOH. mols H2SO4 = M x L = approx 0.01 mols NaOH = M x L = approx 0.012 For 0.01 mols H2SO4 you need 0.02 mols NaOH and you don't have that much so NaOH must be the ...
October 23, 2014

Chemistry
HNO3 + KOH ==> KNO3 + H2O mols HNO3 = M x L = ? mols KOH = same as mols HNO3 because the ratio of mols is 1:1 from the balanced equation. Then M KOH = mols KOH/L KOH. You know M and mols, solve for L and change to mL as you wish.
October 23, 2014

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute and solve for q in J and convert to kJ. 600 mL is 600 g for mass.
October 23, 2014

chemistry
Note the correct spelling of celsius. Did you mean 1 mole instead of 1 mile? I will assume you did. Use PV = nRT and solve for V in L. The problem says to ignore volume of liquid water so you call that zero. Then work = -p(Vfinal-Vinitial) The unit is L*atm. If you want to ...
October 23, 2014

Chemistry
I'll bet those values in the problem are in kJ/mol so no conversion to kJ is necessary.
October 23, 2014

Chemistry
I think the -1679.54 is ok. That's for 1 mol CH4. If you will note 1 mol produces 1,679 (is that J or kJ). Probably kJ. But then you correct for having only 0.1 mol and you obtained MORE? How can that be? If your number is for 1 mol and you have only 0.1 mol you must get ...
October 23, 2014

Chemistry
mols Rh = grams/molar mass = ? q = mols Rh x specific heat x (Tfinal-Tinitial)
October 23, 2014

Chemistry
15.57 kJ/g x 2.5 g = Ccal x (Tfinal-Tinitial) Substitute and solve for Ccal.
October 23, 2014

Chemistry
http://www.jiskha.com/display.cgi?id=1414094876
October 23, 2014

Chemistry
q Al = mass Al x specific heat Al x (Tfinal-Tinitial) q H2O = mass H2O x specific heat H2O x (Tfinal-Tinitial) Note: If you use specific heats in J/mol*K then you must use mass in mols and not grams.
October 23, 2014

Chemistry (urgent)
%Cl in C7H6Cl2 = (2*35.44/161.03)*100 = 44.02% or 44.0% Cl to 3 s.f. %Cl from AgCl data. mols AgCl = g/molar mass = 0.718/143.32 = 0.005. mols Cl = 0.005. g Cl = 0.005x 35.44 = 1.41E-4. %Cl in C7H6Cl2 = (g Cl/mass sample)*100 = (1.41E-4/0.805)*100 = 22.05% or 22.1% to 3 s.f. ...
October 23, 2014

SCIENCE FOR 7TH GRADE
Here is a list of about 10 sites. Look at them to find MANY ideas. Pick the one you like the best. https://answers.yahoo.com/question/index?qid=20090924133042AAF1vNJ
October 23, 2014

Chemistry
CH4 + 4F2 ==> CF4 + 4HF dHrxn = (n*dHf products) - (n*dHf reactants) dHrxn = [(1*-679.9) + (4*-268.61)] - [(1*-74.8) + (4*0)] Solve for dHrxn in kJ for 1 mol Then determine the limiting reagent (which I think is F2 but you should confirm that), determine the amount of CH4 ...
October 23, 2014

chem
It's easier if you type in the numbers. Say XC2H3O = 0.3 so that means XH2O = 0.7 Take enough sample to be 1.00 mol so grams H2O in 0.7 mol = 18 x 0.7 - about 13 g (but you need to be more accurate) and that is 0.013 kg. So m = mols/kg solvent = 0.3/0.013 = ?
October 23, 2014

Chemistry
Did you miss my response below or is there something you didn't understand?
October 23, 2014

Chemistry
heat gained by rod + heat lost by H2O = 0 [mass rod x specific heat rod x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Tf.
October 23, 2014

Chemistry
q = 7.85 kJ/K x (303.35-298.30) = 39.01 kJ So 39.01 x (molar mass caffeine/0.84) = ? kJ/mol caffeine.
October 23, 2014

Chemistry
heat lost by coin + heat gained by H2O = 0 [(mass coin x sp.h Ag x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Tfinal if it is Ag
October 23, 2014

Chemistry
1 m^3 = 1000 L so 145 m^3 = 145,000 L = 145,000,000 mL 145,000,000 grams. q needed = mass H2O x specific heat H2O x (Tfinal-Tinitial). Substitute and solve for q in J.
October 23, 2014

Chem
2(NH2)2CO +3O2 ==> 2CO2 + 2N2 + 4H2O dH = -632.2 kJ/mol*2 mol = 1264.4 kJ/2 mol urea or 4 mols H2O. dH for 1 mol H2O is 1264.4/4 kJ.
October 23, 2014

Chemistry
The first 5.42 degrees C is due to the calorimeter. Total heat for 7.49 C is 20.50 kJ x (7.49/5.42) = 28.329 kJ for combustion CH3OH in that calorimeter. The difference is about 7.8 kJ but you can do that more accurately. Then 7.8 kJ x (32/1.25) = ? kJ/mol Check my work.
October 23, 2014

Chemistry
........HCl + NaOH ==> NaCl + H2O mols HCl = 0.1 x 1.00 = 0.1 mols NaOH = 0.1 x 1.00 = 0.1 mols H2O produced = 0.1 q = mass x specific heat H2O x (Tfinal-Tinitial) q = 200 x 4.184 x (29.8-23.0) That gives q for 0.1 mol in J. Convert to kJ/mol if desired.
October 23, 2014

Chemistry
You want to calculate Qsp and compare that with Ksp. Ba(NO3)2 + K2CrO4 You are given concns before mixing. After mixing each is diluted by factor of 2. New concns are (Ba^2+) = 1E-5M x (10 mL/20 mL) = ? (CrO4^2-) = 1E-3 x (10 mL/20 mL) = ? Plug those new concns and calculate ...
October 23, 2014

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
October 23, 2014

chemsitry
Not only have you solved the problem correctly but you have arrived at the correct answer.
October 23, 2014

CHEM
I think I worked this for you last night. First you need to correct the equation to 2Mg + O2 --> 2MgO mols O2 = grams/molar mass = 16/32 = 0.5 0.5 mol O2 x (2 mol Mg/1 mol O2) = 0.5 x 2/1 = 1 mol Mg
October 23, 2014

CHEMISTRY
mols O2 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols O2 to mols Mg.
October 23, 2014

Chemistry
NaCl(aq) + AgNO3(aq) ==> AgCl(s) + NaNO3(aq) mols NaCl = g/molar mass = approx 0.09 but you need to work each step and obtain better accuracy for the answers. All of the following numbers I've made are estimates. mols AgNO3 = g/molar mass = approx 0.02 The net ionic ...
October 23, 2014

Chemistry
26,500 J heat initially. To melt all of the ice we use up mass ice x heat fusion ice = 5.44g x 334 J/g = 1817 J which leaves 26,500- 1817 = 24683 J for heating the water at zero to some higher T. To raise T of zero H2O to 100 C requires mass x specific heat H2O x delta T = 5....
October 23, 2014

Chemistry
What kind of % is that? % by mass or m/v? I'll assume percent by mass. Convert 5% solution to M. 5.00% w/w means 5 g NaOH/100 g solution. 5g NaOH = how many mols. mols = grams/molar mass = 5/40 = 0.125 mols. What's the volume. mass = volume x density or v = m/d = 100g/...
October 22, 2014

Chemistry
dE = q + w You know q. w is -p(Vfinal-Vinitial) You have 7 mols gas on the left at 22.4 L/mol if this is at STP. You have only 4 mols gas on the right. That should give you Vfinal and Vinitial and work will be in units of L*atm. Multiply that by 101.325 to convert L*atm to J. ...
October 22, 2014

Chemistry
Are you sure this is potassium manganate or should you have written potassium permanganate.
October 22, 2014

Chemistry
Take a 100 g sample which gives you 30.46% N 69.54% O Convert to mols. 30.46/atomic mass N - about 2.2 but you can do it more accurately. 69.54/atomic mass O = about 4.4 Now find the ratio of the two to each other with the smaller number being no less than 1.00. You can see ...
October 22, 2014

Chemistry
Fe + O2 ==> FexOy 6.25g + ? = 8.15g Therefore, the amount of oxygen added must be 8.15-6.25 = 1.90. %Fe = (6.25/8.15)*100 = about 77% but you can (and must) do that more accurately. %O = (1.90/8.15)*100 = about 233%. Do all of these plus all that follows more accurately. ...
October 22, 2014

Chemistry (urgent)
I assume that is magnesium oxalate but I don't know that. Also,I assume you meant potassium manganate and not permanganate. MnO4^2- + C2O4^2- + H^+ ==> H2O + CO2 + Mn^2+ Balance the equation. 100 cc C2O4^- but you don't show the molarity of the oxalate solution.
October 22, 2014

Chemistry
We can't draw diagrams on this forum but if you will google "titration curves" you will get good looking pictures.
October 22, 2014

Chemistry
There is no way to calculate the identity of the limiting reagent because you don't list any values for the concentrations.
October 22, 2014

San Bernardino valley college
Substitute the value of h in the first equation into the second equation as follows: 1/2(5L-3)*L = 34 Now solve for L, then h.
October 22, 2014

San Bernardino valley college
The subject is not San Bernadino valley College. Let L = length and h = height ------------------ h = 5L-3 1/2(hL) = 34 Solve for h and L.
October 22, 2014

Chemistry
Ag(s) + Fe^3+ ==> No reaction.
October 22, 2014

Chemistry 111
2C2H6 + 7O2 ==> 4CO2 + 6H2O mols ethane = grams/molar mass = approx 0.0.57 but you should confirm this and all of the others that follow because I estimate. mols O2 = 107/32 = 3.34 Now convert mols ethane to mols CO2. That's 0.57 x (4 mols CO2/2 mols C2H6) = 0.57 x 2 = ...
October 22, 2014

Chemistry
w = -p(Vfinal-vinitial) w = -(4.0)(5.0-14.0) w = -4.0*-9 = +36 L*atm If you want to convert to J multiply by 101.325.
October 22, 2014

chemistry
So how much of this do you know how to do. You're just throwing work up here.
October 22, 2014

Chemistry
I don't see an apparatus
October 22, 2014

Chemistry
I can do a but not b,c,d. No diagram.
October 22, 2014

Chemistry
See your other post.
October 22, 2014

Chemistry
Where are you stuck? What do you not understand about how to do this?
October 22, 2014

Chemisty
I believe ascorbic acid is a diprotic acid which I will label as H2A. Total mols NaOH used = M x L = approx 0.00353 mols NaOH. The solution contained 1.45E-5 mols ascorbic and that will use 2*1.45E-5 = 2.90E-5 mols NaOH. That leaves 0.003531-2.90E-5 = 0.00350 for mols NaOH to ...
October 22, 2014

Chemisty
You have 0.0350 L x 0.175M = about 0.006125 mols H2SO4. It will take 2x that for mols NaOH
October 22, 2014

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