Tuesday
January 17, 2017

Posts by DrBob222

Total # Posts: 53,873

Chemistry
John, I don't believe you have all of the information listed. You can do b but not a or c with the information listed.
November 13, 2016

chem 1211
q in J = mass H2O x specific heat H2O x delta T. Careful that mass H2O and specific heat H2O are in the same units.
November 13, 2016

Chemistry
If Qsp > Ksp, a ppt will form. So what is Qsp? You are mixing two solutions. That changes the concentrations of both. To what? You are diluting 0.008 M K2SO4 from 650 mL to (650+ 175) = 825 mL. So final (K2SO4) = (SO4) = 0.008 x (650/825) = ? (Ag2SO4) = ? You don't know...
November 13, 2016

Chemistry
First I doubt you determined the wavelength. Probably the wavelength was set or you set it to some desired number. I suspect the 0.178 was the absorbance you read from the spectrometer. Any, one of that really matters. So M = 2.3E-5 what? Is that 2.3E-5 M Fe. I will assume so...
November 13, 2016

Chemisry
I don't think so. The black/green color is due to a little Cu that goes into solution. Rubbing HALF the Cu off and exposing the half Zn and half Cu surface still leaves some of the Cu to react.
November 13, 2016

chemistry
There are 6.022E23 atoms in a mole of atoms and 6.022E23 molecules in a mole of molecules. So 3.011E23 atoms x (1 mol/6.022 atoms) = mols He. b. I don't know. I suspect you made a typo and this is meant to be CO2. c. This is done the same way as part a. I don't get the...
November 13, 2016

chemistry
80 proof means 40% v/v alcohol. % v/v means 40 g solute/100 mL solution. So if 40 g alcohol are in 100 mL, how much is in 1000 mL?
November 12, 2016

just anothe way---chemistry
How many mols do you want? That's mols = M x L = 0.03 x 0.250 = 0.0075 mols. Then 0.0075 mols x 101 g/mol= ?
November 12, 2016

chemistry
1.07 g/mL x ?# mL x 0.10 = 18.50 g. Solve for ? mL.
November 12, 2016

chemistry
mols = grams/molar mass. You know molar mass and grams, solve for mols. Then M = mols/L. You know mols and M, solve for L.
November 12, 2016

Chemistry
a. q = mass H2O x specific heat H2O x (Tfinal-Tinitial) b. q = mass ice x heat fusion ice c. q = mass H2O x heat vaporization H2O
November 11, 2016

chemistry
What's STD?
November 11, 2016

Chemistry
Can't do it. You need the concentration of the FeSO4 solution.
November 11, 2016

Chemistry
AgNO3(s) + H2O --> Ag^+(aq) + NO3^-(aq)
November 11, 2016

Analytical chemistry
Because the Ag^+ will ppt with AgCl and Ag2SO4 is rather insoluble, also.
November 11, 2016

Chemistry (molarity)
mols = M x L = ?
November 10, 2016

Chemistry
Use mL1 x M1 = mL2 x M2 and it will work out OR, logic. Logic goes this way. 5.00M x (2.00/10.00) x (3.00/25.00) = ?
November 10, 2016

Chemistry (molarity)
I think the question MAY (that's MAY) not be worded properly. Two scenarios. 1. IF the question is stated properly, then the molarity of the KHP solution created by added 35 mL water instead of 25 mL water is decreased. As Mia notes, M = mols/L and if L is larger than M is...
November 10, 2016

chem
Actually I don't think it makes any difference; however, I like to write it as [Xe] 4f14 5d3 6s2 for this shows a plausible oxidation state of +5.
November 10, 2016

Chem 104
I'm sorry but I can't decipher this post. I see you want the molarity of the KHP solution but "mass per liter in 100 mL water" and "drop ml-20" don't mean anything to me.
November 10, 2016

CHEM 120
pH = pKa + log (base)/(acid) 9.00 = pKa + log b/a You get pKa from Kb. Convert Kb to pKb; then pKa + pKb = 14 and solve for pKa. Substitute (base) from the problem and solve for (acid), then convert (acid) to grams NH4NO3. Post your work if you get stuck.
November 10, 2016

chemistry
https://answers.yahoo.com/question/index?qid=20120208064619AAS4jyl
November 10, 2016

Chemistry
See your other posts.
November 10, 2016

Chemistry
See your other post.
November 10, 2016

Chemistry
a. mols CO2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CO2 to mols CH4. Now convert mols CH4 to grams. g = mols x molar mass = ? g CH4. b doesn't make sense. grams mols???
November 10, 2016

chemistry
Look up the electronegativity and subtract. The larger difference means a more ionic bond.
November 10, 2016

Chemistry
2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols NaOH = M x L = ? Look at the coefficients in the balanced equation. 1 mol H2SO4 = 2 mols NaOH; therefore, mols NaOH/2 = mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and L, solve for M.
November 10, 2016

Chemistry
Isn't this very close to this problem I showed you earlier? http://www.jiskha.com/display.cgi?id=1478745034
November 9, 2016

Chem 1020
Same type problem. http://www.jiskha.com/display.cgi?id=1478745034
November 9, 2016

Chem1020
http://www.jiskha.com/display.cgi?id=1478745034
November 9, 2016

Help?? Chemistry?
You've done step 1. Step 2. mols KOH = M x L KOH = ? Step 3. Using the coefficients in the balanced equation, convert mols KOH to mols H3PO4. You can see that mols H3PO4 = 1/3 mols KOH Step 4. Then M H3PO4 = mols H3PO4/L H3PO4 = ?
November 9, 2016

Chem 1020
The coefficients tell you that. 2.57 molx Na x (1 mol Na2O2/2 mols Na) = ? Note how mols Na in the numerator cancels with the mols Na in the denominator. That leaves mols Na2O2 in the numerator as the only unit left; you have converted mols Na to mols Na2O2.
November 9, 2016

Chemistry
KOH + KHP ==> H2O + K2P. mols KHP = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KHP to mols KOH. That's a 1:1 ratio; therefore, ? mols KHP = the same mols KOH. Then M KOH = mols KOH/L KOH. You know mols and L, solve for M
November 9, 2016

Chemistry
mass = volume x density. mass Zn = 1 x density Zn (you will need to look that up). mass Cr = 1 x density Cr. Look up density Cr also. Then subtract to find mass difference.
November 9, 2016

Chemistry
Mg + 2HOH ==> Mg(OH)2 + H2 mols Mg = grams/molar mass = ? Using the coefficents in the balanced equation, convert mols Mg to mols H2O Then grams H2O = mols H2O x molar mass H2O = ?
November 9, 2016

Chemistry
CaCl2 + Na2SO4 ==> CaSO4 + 2NaCl mols CaCl2 = M x L = ? Convert to mols Na2SO4. That is ?mols CaCl2 x (1 mol Na2SO4/1 mol CaCL2) = ?mols CaCl2 x 1/1 = ? Then M Na2SO4 = mols/L. YOu know M and you know mols, solve for L and convert to mL.
November 8, 2016

Chemistry
% w/w = (grams solute/grams solution) x 100 = ?
November 8, 2016

chemistry
What is your main problem with this question? Do you know what these compounds are? How they react with water?
November 8, 2016

Chemistry
Why don't you look up the Law of conservation of mass and see what it means?
November 8, 2016

chem 15
1 ppm = 1 mg/L; therefore, 175 ppm = 175 mg CaCO3/L. Convert to grams Ca ions. Convert to mols Ca M = mols Ca/L solution.
November 8, 2016

chem 15
%w/w = (mass solute/mass solution)*100 = ?
November 8, 2016

Chemistry
Check your post. Are you sure that is lead(IV) acetate and not lead(II) acetate. The ppt will be lead(II) chloride, PbCl2, and not PbCl4.
November 7, 2016

Chemistry
You make a set of standards (solution of known concentration of the molecule/ions you want to determine), run them through the same procedure you will use on the unknowns, then measure the absorbance of each. Plot A on the y axis and mg/mL on the x axis. That is your ...
November 7, 2016

Chem
Should be As^3-. Those extra electrons repel each other and the other electrons in the outside shell and that causes the ionic radius to be larger.
November 7, 2016

chemistry
Not so. mols P4 = 20/molar mass P4 = ? mols Pbr3 = ?mol P4 x (4 mols PBr3/1 mol P4) = ? For grams Br2, it isn't 2.93. mass Br2 = volume x density = 50 mL x 2.93 g/mL = ? Then mols Br2 = g/molar mass = ? Convert mols Br2, as above, to mols PBr3 . The smaller number will be ...
November 7, 2016

Weird question science
Right, but I don't know that it's such a weird question.
November 7, 2016

chemistry
mass = volume x density or vol = mass/density vol Au + vol Ag = total vol Let x = mass Au then 9.35-x = mass Ag (x/19.3) + (9.35-x)/10.5 = 0.654 Solve for x = mass Au, then x/19.3 = vol Au.
November 7, 2016

chemistry
See your other post above. We appreciate it when you use the same screen name; we can help you better and faster that way.
November 7, 2016

chem
1 = -log (H^+) so for pH 1, (H^+) = 0.1M and for 1 L of that, mols HCl = M x L = 0.1 x 1 = 0.1 mol. 2 = -log (H^+) (H^+) = 0.01 M and mols HCl = 0.01M x 1 L = 0.01 mols. Then 0.1 mol HCl - 0.01 mol HCl = 0.09 mols HCl to be removed. 2HCl + CaCO3 ==> CaCl2 + H2O + CO2 mols ...
November 7, 2016

Chemistry
Is this just a "I wonder what would happen if" from a bunch of kids sitting around at night with nothing to do except thing up absurd questions.
November 6, 2016

Chemistry
1. Write the balanced equation. C2H5OH + 3O2 ==> 2CO2 + 3H2O 2. Convert 760 g ethanol to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols ethanol to mols CO2. That's ?mols ethanol x (2 mols CO2/1 mol ethanol) = ? 4. ...
November 6, 2016

Chemistry
You're right that C = 4.22E-5 M. So M x L = mols = 4.22E-5 mol/L x 2E-3 L = mols X in that final 2 mL sample that was measured. But that also is the mols in that 300 uL taken from the original sample. Convert to grams. That is g = mols x molar mass = ? That gives you grams...
November 6, 2016

chemistry
You need to look up the solubility of NaCl in water at 80 C, then assign saturated, unsaturated, supersaturated
November 6, 2016

Chemistry
2H2O ==> 2H2 + O2 mols H2O = 4.307/18 = ? mols O2 = ?mols H2O x (1/2) g O2 = mols O2 x molar mass O2 = ?
November 5, 2016

Chemistry
Same problem as above. Just different numbers.
November 5, 2016

@ Steve--typo I think---chem.
I agree with almost all of your work. I also would agree that working it as a math problem is a lot easier than as a chemistry problem. I did it as a chem problem because it was labeled chem. While the mols Ar = 1.2 it is 1.2 both in the initial mixture as well as the final ...
November 5, 2016

chem.
Steve has worked this as a math problem (because he is a math person). I assume the title of chemistry for the question you may want to work it as a chemistry problem. Do it this way. BTW, I agree with Steve's answer EXCEPT for the 1.5 mols. If mols Ar are 1.2 in the ...
November 5, 2016

Chemistry
Since Sn ==> Sn^2+, then if M Sn^2+ is 0.65, so mols Sn^2+ = M x L = 0.65 x 0.023 = ? and same mols Sn to have started the process. Then g Sn = mols Sn x atomic mass Sn = ?
November 5, 2016

chemistry
CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 mols CaCO3 = grams CaCO3/molar mass CaCO3 = ? mols CaCl2 = mols CaCO3 since 1 mol CaCO3 produces 1 mol CaCl2. Then g CaCl2 = mols CaCl2 x molar mass CaCl2 = ?
November 5, 2016

Chemistry Solutions
Your post just isn't clear. I can prepare almost any number of mL from 59 g NaOH but of WHAT concentration. Do you mean to start with 59 g NaOH and ask how many mL of 19.4M NaOH can be prepared from that? If so then mols NaOH in 59 g = grams/molar mass = 59/40 = 1.475 mols...
November 5, 2016

chemistry
0.025 mg = 25E-3 g Pb. mols Pb = grams Pb/atomic mass Pb. 1000 mL H2O x 1.00 g/mL = 1000 g = 1 kg. molality = mols Pb/kg H2O
November 5, 2016

chemistry
p = mv
November 5, 2016

chemistry
wavelength = h/mv
November 5, 2016

Chemistry
(P1V1/T1) = (P2V2/T2)
November 5, 2016

Chemistry
Also we assume that all of the ice melts. q1 = heat needed to raise T of cube at -13.3 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice at zero C to liquid water at zero C. q2 = mass ice x heat fusion. q3 = heat needed to raise T of...
November 4, 2016

chemistry
Use PV = nRT. You know P, V, R and n. n = grams/molar mass. Solve for T (in kelvin).
November 4, 2016

chemistry
There is no reaction. Look up the solubility of these. KNO3 is soluble Ba(C2H3O2)2 is soluble. Now look at the possible products if they react as double displacement. KC2H3O2 is soluble and Ba(NO3)2 is soluble. Neither of the possible products is a gas. Neither is a weak ...
November 4, 2016

Chemistry 101
I don't know the details of the experimental set up.
November 4, 2016

chemistry
1000 is the volume of the solution. Since you want M, that means you want mols solute/L solution. 1000 is volume of solution. 1000 mL x density in g/mL = grams solution. 1000 x g/mL x (%/100) = grams solute. 1000 x g/mL x (%/100) x (1/molar mass solute) = M where grams solute/...
November 4, 2016

Tricky Math Question
My two year old calculator gives an answer of "invalid".
November 4, 2016

chemistry
That's right. Count the electrons and there are 57 but the configuration is not right for La.
November 4, 2016

chemistry
You need to know the rules. Here is how you do it. The rules are: n = 1,2,3 etc in steps of whole numbers. ell (I can't write the script l) is 0, 1, 2, etc in steps of whole numbers but never more than n-1. or less than 0 mell = -ell to + ell in steps of whole numbers (...
November 4, 2016

chemistry
First, what is the M of the 70% HNO3. That's 1.36 g/mL x 1000 mL x 0.70 x (1/63) = ? M1 Then M1 x mL1 = M2 x mL2 M2 is 0.250; mL2 = 1000 mL, solve for mL1.
November 4, 2016

Chemistry
I don't see a question here.
November 3, 2016

Chemistry
https://en.wikipedia.org/wiki/Elimination_reaction
November 2, 2016

Chemistry 11
g Cu(NO3)2 = 3.9 g H2O = 5.0-3.9 = 1.1 mols Cu(NO3)2 = 3.9/187.5 = 0.0208 mols H2O = 1.1/18 = 0.0611 You want n mols H2O/1 mol Cu(NO3)2 So 1 mol Cu(NO3)2 = 0.0208/0.0208 = 1.000 n mols H2O = 0.0611/0.0208 = 2.94. Round that to a whole number of 3.0 Formula is Cu(NO3)2*3H2O
November 1, 2016

chemistry
(62.9298*0.6909)+(x*0.3091) = 63.546 Solve for x.
October 31, 2016

Chemistry
Assume any gram size you wish; i.e., say 5g He and 5g Xe (that is 50% by mass). Then n He = grams/atomic mass = ? n Xe = grams/atomic mass = ? total mols = ? XHe = nHe/total mols and XXe = nXe/total mols. Use PV = nRT and solve for total P of the system usig total mols. Then ...
October 29, 2016

Chem
Use PV = nRT
October 28, 2016

Chemistry
First, calculate M NaOH. mols NaOH = grams/molar mass = ? M = mols/L = mols/0.1 L = ? That gives you the (NaOH) and that is the same as the (OH^-) Now, pOH = -log(OH)^- and pH + pOH = pKw = 14. Calculate pH from this.
October 28, 2016

Chem
NaN3 ==> Na + 3/2 N2 Use PV = nRT. n = grams NaN3/molar mass NaN3. Convert that to mols N2 and plug that into PV = nRT; Solve for V. Then work = pdV and the sign will be negative since the system is doing work in the expansion.
October 28, 2016

Is this homework dump?==chemistry
I've answered enough of these. You've shown no work, no thought, no nothing. I'll be glad to help but no more freebies with me doing all of the thinking.
October 28, 2016

AP Cemistry
I hope you saw my correction for the bath tub of water. I picked up the dH for H2O2 and not H2O. My eye sight isn't that good anymore and those little subscripts are difficult for me to see. At any rate, I think the big problem you had with that was correcting J to kJ in ...
October 28, 2016

AP Cemistry
For an ideal monatomic gas, Cp is (5/2)R. You can read about it here. In fact, several links you can get by Googling "heat capacity ideal gas" explains this better, I think, than the one I'm giving you. http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/shegas.html
October 28, 2016

chemistry
How much heat was generated. 3947.0 kJ/mol x (1.311/16.59) = q Then q = Ccal*delta T Substitute and solve for Ccal.
October 28, 2016

chemistry
Same type problem as hexane
October 28, 2016

chemistry
http://www.jiskha.com/display.cgi?id=1477618485
October 28, 2016

chemistry
Scroll down and find the post I made for Sam. Same problem. It isn't the first post you see for Sam the the one for same below that.
October 28, 2016

chemistry
heat gained by cool water + heat lost by warm water = 0 [mass warm water x specific heat H2O x (Tfinal-Tinitial)] + [mass cool water x specific heat H2O x (Tfinal0Tinitial)] = 0 Substitute and solve for Tf.
October 28, 2016

Chemistry
See your earlier post.
October 28, 2016

Chemistry
I have always used this one. Works every time. 1.02 g/mL x 1000 mL x (%/100) x (1/molar mass NaOH) = M You can do it piecemeal if you wish. M = mols/L. You know M and 1L, solve for mols. grams NaOH = mols x molar mass gives you grams solute. density of the 1 L gives you grams ...
October 28, 2016

Chemistry
2 OCl^- + 2e + 4H^+ ==> Cl2 + 2H2O 2Cl^- ==> Cl2 + 2e When you add these two you end up with twice the coefficients so divide everything by 2. I do it this way because it's easier to explain to students and then divide by 2; however, you can do it from the beginning ...
October 28, 2016

chemistry
I showed you how to do this last night Sam.
October 27, 2016

Chemistry
mass HCl needed is 1000 kg x 0.42 = 420 kg or 420,000 g HCl, then mols HCl = 420,000/molar mass HCl = ? Using the coefficients in the balanced equation, convert mols HCl to mols H2SO4. Then grams H2SO4 (at 100%) = mols H2SO4 x molar mass H2SO4 = ? Since it is only 90% pure, ...
October 27, 2016

chemistry
See your previous post. Same formula.
October 27, 2016

chemistry
q = mass C6H15 x specific heat x delta T Substitute and solve for specific heat.
October 27, 2016

chemistry
..Ba(OH)2 + 2HCl ==> BaCl2 + 2HCl mols Ba(OH)2 = 0.060 x 0.300 = 0.18 mols HCl = 0.060 x 0.600 = 0.036 mols Ba(OH)2 left = 0 mols HCl left = 0 mols H2O formed = 0.036 q = dH = mass H2O x specific heat H2O x (Tfinal-Tinitial) Then convert J to kJ. That is ? kJ for 0.036. To ...
October 27, 2016

chemistry
dE = q + w You know dE and work. Solve for q. Then q = mass gas x specific heat gas x (Tfinal-Tinitial) Substitute and solve for speific heat.
October 27, 2016

chemistry
[mass cool H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass warm water x specific heat water x (Tfinal-Tinitial)] = 0 Substitute and solve for Tf.
October 27, 2016

Chemistry
mols CH4 = grams/molar mass. Then q produced = 890 kJ/mol x ? mols from above = ? Then q produced = mass H2O x specific heat H2O x (Tfinal-Tinitial)
October 27, 2016

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