# Posts by DrBob222

Total # Posts: 54,792

Biochemistry
Your question is not clear to me.

Chemistry
I don't think you have enough information. How much PCl5 do you have (pressure or M)?

chemistry
(1/wavelength) = RZ^2(1/n^2 - 1/n^2) (1/wavelength) = RZ^2*(1/1^2 - 1/x^2) and solve for x. R = Rydberg constant = 1.0973732 The first n is n = 1 and the second n is n = 2; that's where the 1/1^2 and 1/x^2 come from. Z is the atomic number of the element; in this case that...

Chemistry
I don't believe this problem can be solved without using the 0.38 J/g*C as a starting point. I looked that up in a table and found the two closest elements were Zn and Cu. Basically, then, we decide which is the right one. ........M + Cl2 ==> MCl2 ....0.5007 + x .....1....

Chemistry
Cu(NO3)2(s) + H2O(l) ==> Cu^2+(aq) + 2NO3^-(aq)

chemistry
I presume the 17% means that work from the milk is 3.0 kJ/g x 390 g x 0.17 = ? kJ of work. Then plug this into work = mgh as shown in the problem and solve for h = height in meters.

chemistry
First you must determine if the Cu goes through a phase change (i.e., melting) before it reaches 337.3, (it doesn't) so q = mcdT

chemistry
Your set up looks ok but I don't get that answer when I do the math using your numbers. I get something like 50.2. By the way, I looked up Fe and found 0.444 but I assume you are using numbers supplied with the problem.

chemistry
q = [mass H2O x specific heat H2O x (delta T)] + (Ccal*delta T)

CHEMISTRY FOR ENGINEERS
Note that you will need to change A to meters; also, wave number = 1/wavelength

Chemistry
You want XNaOH = 0.03. Then 0.03 = mols NaOH/[mols NaOH +(mols H2O-mols NaOH)] If you let y stand for mols NaOH, this becomes 0.03 = y/[y+(100/18)-y] Solve for y = mols NaOH. Post your work if you get stuck.

Chemistry
I don't think you typed all of the problem/question. You get mass H2O from mass = volume x density and that will answer your posted question. However, most of these problems want to calculate delta H, usually in kJ/mol. That is done as follows: q = mass H2O x specific heat...

Analytical chemistry
A good factor to remember is 1 ppm = 1 mg/L so 1000 ppm would be 1000 mg/L So you want1000 mg (that's 1 gram) MgCO3 in a L of solution.

chemistry
1 ppm = 1 mg/L 1 ppm = 1 mg x (25/1000) = 0.025 mg/25 mL. You want 0.02 ppm so 0.02 x 0.025 = ? mg solute in 25 mL solution.

Chemistry
I don't know your problem but all you need to do is to think of any sentence starting with that "next" letter. The following won't went a Pulitzer Prize but it answers the question. Now is the time, Or any time for that matter, No matter how little or late, ...

chemistry need help
Cr^3+ + 4H2O==> CrO4^2- + 3e + 8H^+ BrO^- + 2e + 2H^+ ==> Br^- + H2O -------------------------------- Multiply eqn 1 by 2 and eqn 2 by 3, then add to obtain the complete balanced redox equation.

CHEMISTRY
a. bubbles b. rxn decreases with time c. ran how of marble chips d. 1. incrase concn HCl 2. increase surface area of chips by breaking them apart into smaller pieces.

@ b.k.---chemistry
Yes, you should use 1/50, calculate as shown above but x will be concentration and not mols. Then convert x = concentration in mols/L to mols.

Chemistry
You don't have enough information to even estimate an answer, much less obtain a real answer. Also, my crystal ball isn't working today.

Chemistry
q1 = heat need to change temperature of solid ice at -45 C to solid ice at 0 C. q1 = mass ice x specific heat solid ice x (Tfinal-Tinitial) q2 = heat needed to change solid ice at 0 C to liquid water at 0 C. q2 = mass ice x heat fusion water. Total q = q1 + q2

Chemistry

Chemistry
I worked this for someone just a day or so ago but I can't find it. Here is a summary. This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. N2 + 3H2 ==> 2NH3 mols N2 = grams/molar mass = ? mols H2 = grams/molar mass...

Chemis6
C6H12O6 → 2C2H5OH + 2CO2 mols ethanol needed = grams/molar mass Using the coefficients in the balanced equation, convert mols ethanol to mols glucose Now convert mols glucose to grams. g = mols x molar mass = ? Post your work if you get stuck.

Chemistry
PCl5 ==> PCl3 + Cl2 Is this 100% reaction or must you use the Keq (which you don't list).

Chemistry
Here is a similar problem. Just change the numbers. http://www.jiskha.com/display.cgi?id=1442613787

Chemistry

Chem
Bob Pursley worked this problem for you that I saw this A.M. Look for it. Click on bob Pursley's answers and you can find it.

chemistry
The answer by Ashley is correct but the equation is not. Here is the correct equation. Zn + 2HCL-->ZnCl2 + H2

Science
distance = rate x time 500 mi = 500 mi/hr x time. Solve for time in hours.

Chemistry
for f.p. delta T =i*Kf*m i = 3 for Na2SO4 m you have look up Kf. Subtract delta T from 0 C to find new f.p. for b.p. delta T = i*Kb*m look up Kb. You have m and i, add delta T to 100 C to find new boiling point.

chemistry
[mass Pb x specific heat Pb x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 The only unknown here is Tfinal

chemistry
See your previous post. Same kind of problem. Post your work if you get stuck.

chemistry
Wouldn't you think N2 < NO2 < KCl?

beginning algebra
Plug in 1 for x and solve for y. Plug in 2ffor x and solve for y. Plug in 3 for x and solve for y. Need more? Plug in a number for x or y and solve for the other.

Chemistry
(V1/T1) = (V2/T2)

Chem
It helps us help you better when you use the same screen name. You didn't do that but see your other post above.

chemistry
KCl + Br2 = no reaction

chemistry
no reaction. Cl2 and KBr is yes, Br2 and KCl none.

chemisty
1 mol of atoms contains 6.02E23 atoms.

chemi

chemistry
1 mol of molecules contains 6.02E23 molecules.

chemistry
See your other posts. All of these are essentially duplicate posts. There are 6.02E23 anythings in 1 mol of anythings.

chemistry
Your question is poorly worded in my opinion. By my definitions, if the H2SO4 is neutralized then there will not be ANY H2SO4 left. What the problem means, I think, is after the addition of that much KOH to that much H2SO4, what is the concn of H2SO4. H2SO4 + 2NaOH ==> ...

Chemistry
It's tough reading with no caps and no periods and/or question marks. Yes, ice water Ti is 0 and Tf final T of solution. Ti for warm water is unknown. Tf is same for ice water and warm water.

Chemistry
heat gained by ice water (you know both Tfinal and Tinitial) + heat lost by warmer water (Tfinal which you know and Tinitial which you don't know) = 0. What's the only unknown in the equation?

Chemistry
Reacted with what? O2? 2C2H2 + 5O2 ==> 4CO2 + 2H2O mols C2H2 = grams/molar mass = ? Then H2O = mols C2H2 x (2 mols H2O/2 mols C2H2) = ? mols H2O Convert mols H2O to grams. grams H2O = mols H2O x molar mass H2O

chemistry
I don't understand what you want with a skeleton equation. But here is the equation. CuCl2 + Li ==> LiCl + Cu You can balance it?

chemistry

Chemistry
Ksp AgI = (Ag^+)(I^-) You know Ksp and I^-, solve for Ag^+. Same for AgBr and AgCl. b part. What is Ag^+ when AgBr first ppts. You calculated that above. Plug Ag+ from the AgBr when it first ppt into Ksp for AgI to find the I^- concn when AgBr starts. Then %I left at that ...

chemistry
dq = mass Au x heat fusion

chemistry
q = mass ethyl alcohol x heat vap

Chemistry
You didn't quit soon enough. The answer is 25 cc = volume. That's the end of the problem. The problem DID NOT ask for the volume of the sides and even if it had the problem didn't say it was a cube with equal dimensions.

chemistry

Chemistry
Almost. I arrived at 14.77 on my calculator, also, but you are allowed only three significant figures. So that 14.77 is rounded to 14.8 g

CHEM 1411
g CaSO4 = 0.0.6168 x (molar mass CaSO4/molar mass BaSO4) = ? Then % CaSO4 = (g CaSO4/mass sample)*100 = ? mass of sample is 0.4550g

Chemistry
0.177, not 0.1777. Then 0.000522 = 0.177/x x = 0.177/0.000522 = 338.9 which rounds to 339. Your line three doesn't follow from line 2. Line 2, except for the extra 7 in the grams is ok. I don't know where the 380 came from. If you had finished and shown how you ...

Chemistry
You leave us in the dark with this. Instead of saying you tried everything, post what you tried and let us find the error. This we're playing guessing games.

Chemistry
I don't see any answer you posted; I see only questions. NaOH + HA ==> NaA + H2O 1 mol NaOH = 1 mol HA so mols NaOH from above = mols HA. Then mols = grams/molar mass or molar mass = grams/mols. If you did g/mols, I suggest you post your work and let us look at it.

Chemistry
mols = M x L = ?

Chemistry
You need to provide us information on what you were doing.

Chemistry
Are you sure that was 0.7374 g Ca? or was it CaCO3. The answer below is for 0.7374 g Ca. 0.7374 x (molar mass Ca citrate/atomic mass Ca) = ? For other metals look for other carbonates that are insoluble; ;i.e., Mg might be one.

honors chem
(0.8020*11.01)+(0.1980*x) = 10.81 Solve for x

Chemistry Plz Help!
Starting with what?

Thermochemistry
What reaction?

chemistry
0.5 what? KCO3. No such animal.

chemistry
Kd = 4.0 = [(x/20)/(100-x)/50] Solve for x = amount in the methylene chloride layer. 100-x is the amount in the water.

chemistry
% mass w/w means (gsolute/total g)*100 = ? [17.35/(17.35+x)]*100 =22.5 Solve for x

Chemistry
A two-step problem. First, determine the specific heat of Co from sample A. q = mass Co x specific heat Co x (Tfinal-Tinitial). The only unknown in this equation is specific heat Co in sample A. Specific heat doesn't change. NHow use the same formula for sample B of Co. q...

Chemistry
I worked a problem just like this last night. Post your work if you run into trouble. http://www.jiskha.com/display.cgi?id=1476638100

Chemistry

Chemistry

Inorganic Chemistry
1.577 M is 1.577 mols/L solution. With density = 1.220 g/mL, then substitute volume and density to find mass of the solution. 1.577 mols AgNO3 x molar mass AgNO3 = grams AgNO3. Then mass solution - g AgNO3 = mass solvent. Convert that to kg. m = 1.577 mols AgNO3/kg solvent

Inorganic Chemistry
1 molal means 1 mol solute in 1 kg solvent. mols solute = 1.00 mols solvent = 1000/18 = ? Total mols = 1.00 + ? from above. Then Xsolute = 1.00/total mols.

homework dump?---chem
I see a lot of question here with no effort on your part. I worked the last two. I can help with the others but HELP is the key word.

Chemistry
(0.788&25.5)+(1-0.788)*X = 29.5 Solve for X.

Chem 125
A multistep problem but simple to do. Use P1V1 = P2V2. For example, calculate the total volume by adding the volumes of each bulb. Don't forget to add in the volume of the tubing. Bulb 1 is 37.0 mL with P of 5.65 atm. So P1 is 5.65, V1 is 37.0 mL, V2 is the total volume ...

Chemistry
mols camphor = grams/molar mass = 25.0/152.24 = approx 0.15 but that's an estimate you should recalculate it. The number of molecules is 6.02E23 molecules in 1 mol so in 0.15 mols there will be approx 0.15 x 6.02E23 = approx 1E21. The formula is C10H16O. There are 27 atoms...

chemistry

Chemistry a level
1. Write and balance the equation. 2MnO4^- + 5C2O4^2- + ? ==> 2Mn^2+ + 10CO2 +? I didn't finish the entire equation (that is I omitted the H^+, electrons, and H2O) BUT I balanced the redox part and that's all you need. 2. mols Na2C2O4 = grams/molar mass = ? 3. Using...

chemistry
Zn is above H in the activity series and silver is below H in the same series.

Chem
pOH = 0.650 -0.650 = log(OH^-) (OH^-) = 4.47 M Ca(OH)2 = 1/2 that or 2.23 M

CHEMISTRY
q = heat absorbed = mass Cu x specific heat Cu x (Tfinal-Tinitial). The sign will be +.

chem
First determine theoretical yield (TY). The actual yield (AY) is given as 1.24g. mols CaCO3 = grams/molar mass = ? Look at the equation. You get 1 mol CaO for every 1 mol CaCO3; therefore, mols CaCO3 from above will give you that many mols CaO. Convert mols CaO to grams. g = ...

chemistry
With all gases in the equation one may use a shortcut in which volumes are considered as mols. Convert 10 L O2 to ? L CO2. 10 L O2 x (3 mols CO2/5 mols O2) = 10 x 3/5 = ? L CO2.

chemistry
1.50 M x (75.0 mL/278 mL) x [139 mL/(139+139)] = ?

Science-chemistry
You need the molar mass of the compound if that is the molar enthalpy of formation of the compound. 100,000 g/molar mass = ? mols compound. What reaction is that -63 kJ/mol for?

Chemistry
heat lost by one + heat gained by other = 0. [mass Au x specific heat Au x (Tfinal-Tinitial)] + [mass granite x specific heat granite x (Tfinal-Tinitial)] = 0 Substitute and solve for only unknown, i.e., Tfinal.

lab chimistry
What compound? What's the experiment?

chemistry 11
If I divide 35.88 by 100 to get 0.3588 and divide that by 1.35 I get 0.266 for salt. sand = 65.11 (which I would round to 65.12 from the numbers); then 0.6512/3.17 = 0.205 Confirm those values and look at your calculations again. As for a negative %error, that just means the ...

chemistry 11

Chemistry
1. What is the concentration of TEOS? 2.What is TEOS?

college chemistry
mols NO = grams/molar mas = ? Using the coefficients in the balanced equation, convert mols nO to mols O2. That ratio is 4 mols NO/5 mols O2. Then remember that one mole of a gas at STP occupies 22.4 L.

Chemistry
mass Fe used = 0.32239. Convert that to mols. mols Fe = g/atomic mass = ? Using the coefficients in the balanced equation, convert mols Fe to mols Cu product. That's ?mols Fe x (3 mols Cu/2 mols Fe) - ?mols Fe x 3/2 = ? Then convert mols Cu formed to grams. g Cu = mols Cu ...

chem
The titration is HCl + NaOH ==> NaCl + H2O mols NaOH used = M x L = approx 0.01 but you need to confirm that.Since the ratio in the titration is 1 mol NaOH to 1 mol HCl, that means mols HCl in that 25 mL aliquot is the same as mols NaOH used to titrate it. Since this was a ...

Chemistry
The advantage is that most of the Mg and Ca ions are removed which means less detergent needed to clean. It also means less "bathtub" ring when the Ca and Mg ions react with soap. The con is that the Ca and Mg ions are replaced with Na ions and most health agencies ...

chemistry
equivalents = grams/eq weight = 4/40 = ? N = eq/L = ?

chemistry
Frankly, I haven't called these the H, or B or C groups. I have used alkali metal group, alkaline earth group, halogen group, noble element group, etc. There is much confusion about how the columns are numbered in the periodic table but if you understand the different ...

Chemistry
Two. There is 1 mol NH4^+ and another 1 mol Cl^-.

chem
I showed you how to do part a last night. You should have posted the entire problem then.

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