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March 30, 2017

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Posts by DrBob222

Total # Posts: 54,305

Chemistry
There are two atoms/unit cell in a bcc and a mole of atoms is 6.02E32 atoms. You make the conversion from atoms to mols.
July 3, 2016

chemistry
How many moles do you need? That's mols = M x L = 0.37M x 0.300 L = ? Then mols = grams/molar mass. YOu know mols and molar mass, solve for grams.
July 3, 2016

Chemistry Help Please!
1. Convert 20 ug/mL to g/L. Take 1000 mL (= 1L) 20 ug/mL x 1000 mL = 20,000 ug in that L. How many grams is that. 20,000 ug x (1 g/1E6 ug) = ? grams. mols = grams/molar mass and M = mol/L. 2. mL1 x M1 = mL2 x M2 30 x 0.03 = mL2 x 0.1M Solve for mL2. That's the mL of the ...
July 3, 2016

chemistry
mols PO4^3- ion = grams/molar mass = 9.5/approx 95 = approx 0.1 but you need to confirm all of that. There are 6.02E23 PO4^3- ions in 1 mol; therefore, there are 6.02E22 mols in the 9.5 g. In 1 PO4^3- there are 31 electrons in the P atom and 4*8 = 32 electrons in the 4 O atoms...
July 3, 2016

Chemistry
mols Al2(SO4)3 = grams/molar mass = ? Then M = mols/L solution. Then N = 6M
July 2, 2016

Chemistry
I wonder if you mean 0.0200 m or 0.002 M? Do you know there is a difference? I will assume you mean M. ..CH3NH2 + HOH --> CH3NH3^+ + OH^- I..0.02.............0..........0 C...-x..............x..........x E..0.02-x...........x..........x Kb = (CH3NH3^+)(OH^-)/(CH3NH2) ...
July 2, 2016

chemistry
It might be best for whom? to give you the answer. We're trying to help you understand the problem. We aren't too interested in giving you the answer. You have a strong acid (HCl) and a very weak acid (HCN). Usually the strong acid predominates and the pH is determined...
July 2, 2016

chemistry
HCl + NH3 ==> NH4Cl mmols HCl = 5 mmols NH3 = 5 So you have a solution of 5 mmols NH4Cl iin 75 mL and M = mmols/mL = 5/75 = 0.0667. The pH of the salt is determined by the hydrolysis of the NH4^+ .....NH4^+ + H2O ==> H3O^+ + NH3 I...0.0667............0.......0 C....-x...
July 2, 2016

chemistry
Moles are what reacts in chemistry. mols = molarity x liters. I prefer to work in millimols so mmols HCl = mL x M = ? The problems tells you M HCl is 0.3 and the mL = 300 so 300 x 0.3 = 90 mmols. Yes, you can use an ICE table and I used an abbreviated one but here is the full ...
July 2, 2016

chemistry
pH = -log (H^+) = -log(HCl) .......HCl + NaOH ==> NaCl + H2O millimols HCl = mL x M = approx 90 mmols NaOH = 50 Excess HCl = 90-50= 40 total volume = 400 mL M = mmols/mL = 40/400 = 0.1 pH = -log(H^+) = ?
July 2, 2016

chemistry
CH3COOH = HAc. Calculate M of the solutions. millimols of each. mmols = mL x M = 100 mL x 10^-3 = 0.1 mmols = 50 x 10^-2 = 0.5 Total = 0.6 M = mmols/mL = 0.6/150 mL = approx 0.004 .....Ac^- + HOH --> HAc + OH^- I...0.004............0.....0 C....-x..............x.....x E..0....
July 2, 2016

Physics/Chem
volume Al or Cu cube = 24 x 24 x 24 = ?cc. mass Al = volume x density = ? mass Cu = volume x density = ? Look up specific heat Al Look up specific heat Cu Energy removed from Al + energy added to Cu = 0 [mass Al x specific heat Al x (Tfinal-Tinitial)] + [mass Cu x specific ...
July 1, 2016

Physics/Chem
This is worked almost the same as the Al/Cu problem above. heat lost by ceramic on cooling is q = mass ceramic x specific heat ceramic x (Tfinal-Tinitial) Then look up heat vaporization liquid nitrogen. joules lost by ceramic = mass N2 x heat vaporization liquid N2. Solve for ...
July 1, 2016

chemistry
I think B<Be<F<K<Rb Look at www.webelements
July 1, 2016

Chemistry
Ni3(PO4)2is insoluble in water solution.
July 1, 2016

Chemistry
Nope. Note correct. The atoms don't balance (4Ce on right and 3 on left as well as 1 S on left and 2 on right) and charges don't balance (10+ on left and 12+ on right). 2Ce^4+ + S^2- ==> 2Ce^3+ + S
July 1, 2016

chemistry
rate 1 = H2 = 60/10 = ? rate 2 = G = 60/37.4 = ? (rate1/rate2) = sqrt(MMG/MMH2) where MMG is molar mass G and MMH2 = molar mass H2. You know molar mass H2. The only unknown is MMG.
June 30, 2016

Chemistry
right. Go the head of the class.
June 30, 2016

Chemistry
http://www.jiskha.com/display.cgi?id=1467126046
June 30, 2016

Chemistry
no way. What are you trying to do? Do you have a density problem?
June 30, 2016

Chemistry
looks good to me.
June 30, 2016

chemistry
You have written the complete ionic equation. To turn this into the net ionic equation just do this. Cancel the ions that appear on both sides. What's left is the net ionic equation. 2Na^+ are on both sides. Cancel. 2NO3^- are on both sides. Cancel. Zn^2+(aq) + 2OH^-(aq...
June 29, 2016

Chemistry
Call ascorbic acid H2A to save typing. First determine the molarity of the NaOH from pH = 14.436. pH = 14.436 so pOH = -0.436. Use pOH = -log(OH^-) and I get OH^- = 2.7 but you need to get a more accurate number and redo the rest of the problem since my work is just an ...
June 29, 2016

chemistry
Use a liquid indicator or feel it. Bases are slippery to the touch.
June 29, 2016

Chemistry
Run a % Cl test, convert to NaCl and compare the mass of the sample with that found in the test.
June 29, 2016

University of Liberia Chemistry 102
You can't plate CuSO4. You can plat Cu metal.
June 29, 2016

Chem
You can look these conversion factors up in tables or on Google. There are 3.785 L/gallon and 1.609 km/mile. So 10.6 km/L x (3.785 L/gallon) x (1 mile/km) = ? Note that you makes these conversions so the unit you have gets canceled and leaves the units you want to keep. You ...
June 28, 2016

Chem
I'm trying to help. That doesn't help me help you. If you tell me where you have trouble I will know where to start.
June 28, 2016

Chem
This looks like a lot of arithmetic. What is it you don't understand?
June 28, 2016

chemistry
% w/w = (g solute/gm soln)*100 = ? (5g/x)*100 = 16.2 x = (500/16.2) = approx 30.9 g solution. g urea + g H2O = 30.9 total. Calculate g H2O to add.
June 28, 2016

Chemistry
So x is 2.
June 28, 2016

Chemistry
http://www.jiskha.com/display.cgi?id=1467098349
June 28, 2016

Biochemistry
You need to know what "this formic acid-sodium formate solution" is.
June 27, 2016

Chemistry
To prepare 10 L of WHAT?
June 27, 2016

chemistry
CH3COOH - acetic acid = HAc CH3COONa = sodium acetate = NaAc BEFORE: you have a 200 mL of 0.1M HAc. The pH is determined by the ionization of the HAc. .........HAc ==> H^+ + Ac^- I........0.1.....0......0 C.......-x.......x......x E.......0.1-x....x......x Substitute the E ...
June 27, 2016

chemistry
OK. So we go with the 0.01 in the initial ICE chart as correct. You have 100 mL of 0.082 M. You want 2 mL of 10 mM (0.01 M) The dilution formula is mL1 x M1 = mL2 x M2 mL x 0.082 = 2 mL x 0.01M mL of 0.082M needed= 2*0.01/0.082 = 0.244 mL.
June 27, 2016

chemistry
I'm confused, too. You show 1M, 100 mL but you then have L x M = (0.1L x 0.1M). So do you mean 100 mL of 1 M or 100 mL of 0.1M? Near the end you have 0.0082 mols/0.1L and that is 0.082 and not 0.82.
June 27, 2016

Organic Chemistry
% aspirin = (0.082/5.00)*100 = ? %caffeine = )0.21/5.00)*100 = ?d etc for acetanilide. For #2, convert grams given in the problem to mols. mol = grams/molar mass = ? Then mol% aspirin = (mols aspirin/0.600)*100 = ? etc. for the others.
June 27, 2016

chemistry
We can't write Lewis dot structures on this forum. Google Lewis dot structure of each of these and you can see how they look.
June 27, 2016

Chemistry
If what you have is a pure compound and not a mixture, yes.
June 27, 2016

Chemistry
20 gm of what?
June 27, 2016

Chemistry
That's why you've been stuck on this question for hours. There isn't enough information. You MUST know how much Na2SO4 there is. This is just like asking "You're driving your car to the supermarket that's down the road 5 miles. How long will it take ...
June 26, 2016

Chemistry
Na2SO4 + BaCl2 ==> BaSO4 + 2NaCl So how much Na2SO4 do you have?
June 26, 2016

chemistry
The s orbital is not degenerate. The p orbital is with pz, px, py orbitals. The d orbital is with 5 orbitals. You can google and get the shapes of the five.
June 26, 2016

Chemistry
If you knew the answer why did you post the question?
June 26, 2016

chemistry
You are correct that both ii and iii are incorrect and for the reason you cite. i is correct. If n = 4, l can be 0,1,2,or 3; ml can be -3.-2,-1,0,1,2,3; ms can be +/- 1/2. Note: for iii, I think you meant to write "l can be 0,1,2,3 or 4." t-4 doesn't make sense ...
June 26, 2016

chemistry
It's a statement about the Heisenberg Uncertainty Principle. That says that if you can know exactly where the electron is sitting, you can not know its velocity. The reverse is true, also. If you know how fast it is traveling, you can not at any instant exactly where it is...
June 26, 2016

chemestry
A quadratic is not required and you can let 0.0667-x = 0.0667.
June 26, 2016

chemestry
First, please spell chemistry right. I'm annoyed. Second, this is a buffer problem for the first addition. They throw you a curve with the second addition because it is NOT a second buffer problem. Here is the scoop. Call acetic acid, CH3COOH, as HAc. millimols HAc = mL x ...
June 26, 2016

Chemistry
Look up the delta Hof values for each, then dHrxn = (n*dHf products) - (n*dHf reactants). This dHrxn will be for 34 g NH3. For 2.5 g it will be dHrxn x (2/34) = ?
June 26, 2016

chemestry
I ASSUME this is a beginning class and they expect you to view H2SO4 as a dibasic acid; i.e., 0.05M x 2 = 0.1M in (H^+). Actually, that isn't right as (H^+) really is closer to o.059M and not 0.1. But we will go with the assumption. Let's call formic acid as HFm to ...
June 25, 2016

CHEMISTRY
If you understand the post below you will know how to do this. I'll check your answers.
June 24, 2016

CHEMISTRY
But you know those answers are wrong. You should follow my rules above to get the correct answers.
June 24, 2016

CHEMISTRY
Here is how you do a couple of them. Then you try the others. Sr and NO3^-1 Sr is a +2 charge. There is no Sr with a +3 charge. Sr(NO3)2. You can see Sr is +2 and 2 NO3^- is -2 so the +2 neutralizes the -2. All compounds will be zero charge and that's how you know what ...
June 24, 2016

Chemistry
Those don't react but if they did it would be this. 2FePO4 + 3Na2SO4 ==> 2Na3PO4 + Fe2(SO4)3 mols FePO4 = grams/molar mass = ? Then using the coefficients in the balanced equation, convert mols FePO4 to mols Fe2(SO4)3. That's mols FePO4 x (1 mol Fe2(SO4)3/2 mols ...
June 24, 2016

CHEMISTRY
I'm sure you mean [NO3]^-, [SO4]^2- etc. Then In(NO3)3, In2(SO4)3, etc. If we could write subscripts very well on this forum the nitrate would be [NO3]-
June 24, 2016

CHEMISTRY
See your other post.
June 24, 2016

Science-chemistry
If %A = 22.22%, then %B = 77.78. Take 100 g sample to give you 22.22 g A 77.78 g B. Convert to mols. 22.22/40 = 0.5555 mols A. 77.78/atomic mass B = ? mols B. You know the ratio is A2B5; re-write this way letting X stand for atomic mass of B. 22.22/40 = 0.5555 x some # = 2 77....
June 24, 2016

chemistry
How many mols do you need? That's M x L = ? mols NaOH. Then grams = mols NaOH x molar mass NaOH
June 23, 2016

chemistry
........BaCrO4 ==> Ba^2+ + CrO4^2- I.......solid.......0.......0 C.......solid.......x.......x E.......solid.......x.......x Substitute the E line into Ksp expression and solve for x = solubility
June 23, 2016

another approach---Chemistry
Calculate % each element. %X = (0.36/0.56)*100 = 64.3% %O = (0.2/0.56)*100 = 35.7% Take 100 g sample to give 64.3 g X 35.7 g O Convert to mols. 64.3/at mass X = ?mols X. 35.7/16 = 2.23 mols O. We know this is in the ratio of 2:3 so, letting X = atomic mass X 64.3/X = ?......*...
June 23, 2016

Chemistry
Use PV = nRT and solve for n. Look up the vapor pressure of H2O at 20 C. It is approximately 20 torr BUT that's just a guess (although a very close guess). Ptotal = pH2O + pAr You know ptotal and pH2O, solve for pAr and use that for P in PV = nRT. Substitute the other ...
June 22, 2016

Chemistry
1 carat = 0.2 g; therefore, 15 carats = 3 g. Then mol = grams/molar mass = ? That gives you mols in the mineral. Since there are 3 mols of Si in 1 mole of the mineral, mols Si will be 3x mols in the mineral.
June 22, 2016

Chemistry
No and yes. You don't need to use dHrxn = (n*dHf products) - (n*dHf reactants) because the problems has already done that for you. For the reaction given dH is -2511.0 kJ and that is for 2 mols of C2H2 or 2*26 = 52 g. So the revised question is if 52 g releases 2511.0 kJ ...
June 22, 2016

Chemistry
mols KCl = M x L = ? mols PbCl2 formed = ?mols KCl x (1 mol PbCl2/2 mols KCl) = ?mols KCl x 1/2 = ? mols PbCl2. Then grams PbCl2 = mols PbCl2 x molar mass PbCl2.
June 22, 2016

chemistry
The ethyl group on both 3 and 4 make the chain one C longer. I can't draw it on this forum but try google the names you have and see how they look then count the longest C chain.
June 22, 2016

chemistry
Take a look at 3 and 4. 3 appears to be a pentanol to me. 4 appears to be a hexanol to me. Check it out.
June 22, 2016

Chemistry
22.4 L NH3 at STP has a mass of 1 mol or 17 grams. So 800 cc (0.800 L) will contain 17 x (0.800/22.4) = ?
June 22, 2016

chemestry
I've done all but the water. You can fill that in. 2Cr2S3 + 30PbO2 + 24H2SO4 --> 30PbSO4 + 2H2Cr2O7 + ?H20 Check it out. Make sure I made no typos.
June 22, 2016

chemestry
I REALLY wish you would spell chemistry right. You've posted the last several days with the wrong spelling.
June 22, 2016

chemistry
right
June 21, 2016

Chemistry
The answer is here. https://en.wikipedia.org/wiki/Free_expansion
June 21, 2016

Chemistry
It is symmetrical in three dimensions so it is non-polar.
June 21, 2016

chemistry
See your other post.
June 21, 2016

Chemistry
What does P = 40% mean? You don't need the density. mols needed = M x L = ? Then grams = mols x molar mass. You know mols and molar mass, solve for grams HF.
June 21, 2016

Chemistry
First, a correction. The Henderson-Hasselbalch equation is pH = pKa + log (base)/(acid). That negative sign is either a typo in the book or by you in the post. What you are asking isn't exactly clear. I think you want to know why a. is the solution a buffer b. why it is ...
June 21, 2016

Chemistry
I don't think the molar mass of the 58.3 mg sample is 122.44 nor do I think you can calculate what it is. The NaClO4 contains Cl35, Cl36, Cl37in this sample. You know the percent Cl36 but you don't know the percentages of the other two (except of course in naturally ...
June 21, 2016

Chemistry
It's all here. The last links defines what an isotonic solution is for NaCl. https://en.wikipedia.org/wiki/Tonicity http://differentmedicalcareers.com/hypertonic-hypotonic-isotonic-solutions/ https://www.google.com/search?q=what+concentration+NaCl+is+isotoinic&ie=utf-8&oe=...
June 21, 2016

chemistry
For the same reason that no reaction every completes. For reversible reactions there is always at least one molecule that is "ready" to reverse direction.
June 21, 2016

chemistry
If you are in beginning chemistry, the easy answer is that it is 0.2M in (H^+) so pH = -log(0.2). Then pH + pOH = pKw = 14 and you get pOH from that. However, that isn't quite right since the second H^+ is not a strong acid and more advanced classes will do it slightly ...
June 20, 2016

chemistry
Ba(OH)2(aq) + 2HCl(aq) BaCl2(aq) + 2H2O (g) molBa(OH)2 = M x L = ? Now using the coefficients in the balanced equation, convert mols Ba(OH)2 to mols HCl. Finally, M HCl = mols HCl/L HCl.
June 20, 2016

Chemistry
K2SO4 = potassium sulfate NH4)F = ammonium fluoride
June 20, 2016

Chemistry
KaKb = Kw. You know Ka and Kw, solve for Kb .
June 20, 2016

chemestry
Please explain what the recipient is. Are all gases 2.4 moles or is that CO and H2 = 2.4 mols.
June 19, 2016

chemestry
.......SO2Cl2(g) ⇄ SO2(g) + Cl2(g) I......1.2..........0........0.8' C.......-x..........x.........x E.....1.2-x.........x......0.8+x Kp = 2.4 = (x)(0.8+x)/(1.2-x) Solve for x and evaluate each of the components.
June 19, 2016

chemestry
P.S. Note the correct spelling of chemistry.
June 19, 2016

chemestry
Essentially one ignores the contribution of H^+ from the HCN but you can calculate how much that is. .......HCN ==> H^+ + CN^- I......1........0.....0 C......-x.......x.....x E......1-x......x.....x For HCl, remember it is a strong electrolyte and ionizes completely...
June 19, 2016

chemestry
Note the correct spelling of chemistry. NH3 + HCl ==> NH4Cl mols NH3 = M x L = 0.1 x 0.05 = 0.005. mols HCl 0.2 x 0.025 = 0.005. You see this is an exact neutralizing solution; you have no HCl or NH3 left and have formed 0.005 mols NH3 in 75 mL solution so (NH4Cl) = 0.005/0...
June 19, 2016

@ kandace---chemistry
I should point out here that your problem makes no sense to me. True that the CO2 bubbled into Ca(OH)2 produces CaCO3 BUT you say the mass of the hydrocarbon is 10 g. So did you start with 10 g hydrocarbon or did the CaCO3 weigh 10 g. I don't call CaCO3 a hydrocarbon but ...
June 19, 2016

chemestry
Use the Henderson-Hasselbalch equation. Note the correct selling of chemistry. ALSO, and this is important, do you man m or M. m stands for molality. M stands for molarity. Also, I don't believe Ka for acetic acid is 1.76 x 10^-6. You either looked it up wrong or y you ...
June 19, 2016

Chemistry
I don't know many who have the solubility tables of thousands of chemicals memorized. I know I don't. Surely you have a table that lists the solubility of KClO3 at 80 C and 10 C. Or perhaps it's a graph that gives those numbers. If you will post those perhaps we ...
June 18, 2016

Organic chemistry
vanillan from vanilla
June 16, 2016

chemistry
What you have looks ok to me. Cr will go to Cr^3+.
June 16, 2016

CHEMISTRY
2F^- --> F2 + 2e -2.87 2I^- ==> I2 + 2e -0.535 But somehow I don't think this is the answer your are looking for. As to WHY the potentials are that way-- I suppose that's the nature of the beast. F^- being such a small ion isn't likely to give up electrons. ...
June 16, 2016

Chemistry
Why didn't you show us how you came up with 1.69. If we don't know how you got there how can we tell where you're going wrong? I cam up with approx 1
June 16, 2016

Chemistry
%bu ,ass = (grams solute/total grams)*100 = ? grams solute = 200 g total grams = 200+500 g = ?
June 15, 2016

Chemistry
1.25 g C/12 = mols C Convert to mols soap. grams soap = mols soap x molar mass soap.
June 14, 2016

chemistry lab
I suppose you meant "weigh". I can't answer because I don't know what you're doing.
June 14, 2016

Chemistry
mass % = g solute/100 g sample. M = mols/L solution. So you have 4.6 g C2H5OH/100 g solution. molar mass C2H5OH = 46 mols C2H5OH in 4.6 g is 4.6/46 = 0.1 mol. What is the volume? That's mass = volume x density or volume = mass/density = 100 g/0.93 = 108 mL or 0.108 L. Then...
June 14, 2016

Chem
There is none in what you have written. If you have water of crystallization it would show something like this: Fe(NO3)2.xH2O where x is 1, 2, 3, or some other whole number.
June 14, 2016

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