Wednesday
October 26, 2016

# Posts by DrBob222

Total # Posts: 53,452

Chemistry
Note the correct spelling of celsius. Use PV = nRT and solve for n, then n = grams/molar mass.
July 27, 2016

chemistry
mL1 x M1 = mL2 x M2 mL1 x 0.5M = 2000 mL x 0.4 Solve for mL1.
July 27, 2016

chemistry
1 ppm = 1 mg/kg and 1 ppb = 1 mg/1000 kg. 15 mg/kg = ? ppb is 1000 more mg.
July 27, 2016

Chemistry
You didn't list any values. The salt will have a pH less than 7; most likely it will be about 4 to 5 that isn't a rule.
July 26, 2016

Che
What are you calling fundamental particles? Do you want electrons, protons, neutrons, or do you want electrons, up quarks and down quarks?
July 26, 2016

Army school math
I don't know how the army does this. Trig? formula. The formula using straight algebra is A = sqrt(p(p-a)(p-b)(p-c) where p is 1/2 the perimeter and a,b,c are the sides. The perimeter is 26 and the base is 6 which makes the other two sides 26-6 = 20 and since it is an ...
July 26, 2016

Chemistry
If you are using M for mols, that won't get it. M stands for molarity. I will assume you meant mols. You have four limiting reagent (LR) problems here. I'll do the first two for you; you follow the plan to do the other two. Zn + 2HCl ==> ZnCl2 + H2 a. 1. mols HCl = ...
July 26, 2016

Organic Chemistry
Two comments: 1. How in the world did this get named as a question in organic chemistry. Helium is about as un-organic as you can get. 2. With regard to Yang's answer. That's a great answer EXCEPT that "all noble gases have the maximum number of electrons possible...
July 25, 2016

Chemistry
I'll do the first one; you do the second. CH4 + 2O2 --> CO2 + 2H2O dHrxn = (n*dHf products) - (n*dHf reactants) If dHrxn is -, rxn is exothermic. If dHrxn is +, rxn is endothermic.
July 24, 2016

chemistry
This is a condensation polymer. I googled "condensation polymer" and this is what I got. Let me be clear that this is copied word for word from the web. I suspect it is found this way in Wikipedia. "Condensation polymers are any kind of polymers formed through a...
July 24, 2016

Analytical Chemistry
No. You have no concn for that so how would you put that on the graph? You look at the A value on the graph, read the concn in mg Fe from the curve, and use that in the final % w/w calculation.
July 22, 2016

Analytical Chemistry
You can do this mathematically but it is easier, I think, to draw a graph for the calibration curve. On the Y axis you place the absorbance which I assume is the "signal" in your post. If not, it might be %T; whatever it is plot it (Absorbance or whatever) on the Y ...
July 22, 2016

Chemistry
mols NaOH = M x L = ? Look at the equation. mols H2SO4 = 1/2 mols NaOH Then M H2SO4 = mols H2SO4/L H2SO4.
July 22, 2016

Chemistry
yes. Good work.
July 21, 2016

Chem
It is difficult in this forum for us to write subscripts and superscripts. Here is what I'll do. The number to the left of the element symbol is the atomic number. The number to the right of the element symbol is the mass number. The way you do these problems is to make ...
July 21, 2016

Chem
Are you telling me that you don't know how to write the equations? The problem TELLS you the products. The first one is CH4 + O2 ==> CO + 2H2O Please state exactly what you don't understand about this problem and I can help you through it.
July 21, 2016

chemistry
Oxalic acid is H2C2O4 and that is diprotic.
July 21, 2016

chemistry
Note the correct spelling of celsius. Why don't you google solubility of N2 at 25 C. That number is all over the place.
July 21, 2016

College Chem.
Here is what I would do. First, add 1 mol NaOH to convert ALL of the H3PO4 to H2PO4^- ion. Keep that 1 mol NaOH in mind. Now look at how we convert H2PO4^- to H2PO4^= ......H2PO4^- + OH^- ==> HPO4^= I.....1 mol.....0.........0 add.............x........... C....-x........-x...
July 21, 2016

Chemistry
First, I have no idea what Chapter 8 says. For question 1, your answers look ok although I wouldn't have answered them exactly as you did. For example, I think ErF3 is reduced. Although 2ErF3 isn't wrong, at least I wouldn't count that wrong on an exam, I would ...
July 20, 2016

Chemistry
A good conversion factor to remember is this. 1 ppm = 1 mg/L So 45 ppm = 45 mg/L. Convert mg to g, then divide by molar mass NO3^- to convert to mols and you have it.
July 20, 2016

Chemistry
I don't what the t stands for.
July 20, 2016

Chemistry
Right, since Kc is given to 3 places, I would calculate M to 3 places; i.e., 2 mols/3 L = 0.667. .......H2 + X2 ==> 2HX I......0....0.......0.667 C.....+x...+x........-2x E......x....x.......0.667-2x Substitute the E line into the Kc expression and solve for x, then convert...
July 20, 2016

Chemistry
m = mols/kg solvent 1.33 = mols/1.5 mols = ? Then grams = mols x molar mass.
July 20, 2016

chemistry
A + [O] ==> B + Ca(OH)2 ==> C 2g.........2.1....1.05......... Ca(OH)2 + 2XCOOH ==> Ca(XCOO)2 + 2H2O mols Ca(OH)2 = grams/molar mass = approx 0.014 but you need to do that more accurately. mols XCOOH must be twice that or about 0.028. mols = grams/molar mass or molar ...
July 20, 2016

Chemistry
A bunch of liters and forever. C isn't very soluble in HCl. It will take even longer than forever if the HCl is dilute.
July 20, 2016

Chemistry
Use PV = nRT. P = 1.19#4/760 atm T = 273 + 21 = ?K Solve for n, then n = grams/molar mass. YOu know molar mass and n, solve for grams.
July 19, 2016

Chemistry
40.7 kJ/mol x #mols H2O = 885 kJ Solve for #mols H2O and convert to grams. g = mols x molar mass
July 19, 2016

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
July 19, 2016

chemistry
You're question is quite general. What do you mean by "what happens" to water. Well, it stays as H2O, it doesn't decompose, liquid water is almost incompressible, etc. You need to clarify the question.
July 19, 2016

Chemistry
The pressure is less, the b.p. is defined as that temperature at which the vapor pressure of the substance is the same as atmospheric pressure; therefore, the boiling point is less because the pressure is less. If you had wanted to figure this out yourself you could have put ...
July 19, 2016

Chemistry
And what is the the molarity of the NaEDTA? Standard, yes, but I don't know what your standard is. My guess would be 0.1M.
July 19, 2016

Chem
(p1v1/t1) = (p2v2/t2) You have p1v1 and t1 on the ground and you have v2 and t2 in the upper atmosphere. The only unknown is the volume at it's height of ascent. Find v2, then the difference in volume is v2-v1 = ? Watch that you keep the units the same (either all torr or ...
July 18, 2016

CHEMISTRY
g C = g CO2 x (atomic mass C/molar mass CO2) = 1.10 x 12/44 = about 0.3 g H = g H2O x (2*atomic mass H/molar mass H2O) = about 0.05 g O = 0.43- g H - g C = about 0.08 Convert to mols. mols C = 0.3/12 = ? mols H = 0.05/1 = ? mols O = 0.08/16 = ? Now find the ratio of these ...
July 18, 2016

chemistry
We can't draw Lewis dot structure on this forum. I can try this way. Draw the Lewis dot structure for H2O. You have O with : on the left, top, bottom, right. An H goes on the left and the bottom which leaves the two electrons on the top and right undisturbed. Now a H ion (...
July 18, 2016

Chemistry
A is a limiting reagent (LR) problem. You know that when you are given amounts for BOTH reactants. You use BOTH to determine which is the limiting reagent, then use the one that is the LR. Right. You have 0.05 mol BaCl2 and you have 0.045 mols K2SO4. a. Convert mols BaCl2 to ...
July 18, 2016

Chemistry
mols Na2O = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Na2O to mols NaOH. That will be mols NaOH = 2 x mols Na2O Now convert mols NaOH to grams NaOH. grams = mols x molar mass
July 17, 2016

Chemistry
July 17, 2016

Chemistry
July 17, 2016

Chemistry
See your other posts. You get better help if you don't change screen names.
July 17, 2016

chemistry
You need to find the caps key and use it. Cu(OH)2 is insoluble.
July 17, 2016

Chemistry
5% m/v means 5 g solute in 100 mL solution. So the patient received 5 g x (5 mL/100 mL) = ?
July 17, 2016

Chemistry
0.4% m/v means 0.4 g solute/100 mL solution 0.4 g NaCl/100 mL x ?mL = 5 g NaCl Solve for ? mL
July 17, 2016

chemistry
1. 7% m/m means 7 g solute in 100 g solution. So you want 75 g solution. How many g solute will that be. That's 7 x (75/100) = 5.25 g solute. Place 5.25 g solute in 75-5.25 = 69.75 g H2O. I like to check these things to see that it really is 7%. (5.25/75)*100 = 7.0% You ...
July 17, 2016

chemistry
For KCl at 50 C. 42.6 g KCl x (35.0g H2O/100 g H2O) = 14.9 which means 14.9 g KCl can be dissolved in 35.0 g H2O. That means it will be saturated since 19.7 g KCl is greater than what will dissolve. 2 and 3 are done the same way.
July 17, 2016

chem II
Are these separate solution? NaCN + H2O ==> Na^+(aq) + CN^-(aq)
July 17, 2016

chemistry
Use PV = nRT and solve for n. Then n = grams/molar mass. You know grams and mols(n), solve for molar mass. Then molar mass/16 = x where Ox is the allotrope.
July 17, 2016

Chemistry
C2H5OH + 3O2 --> 2CO2 + 3H2O
July 17, 2016

typos--Chemistry
Note: Dr Rebel has reversed the Ka values (as well as using my estimates instead of the tabular values for Ka) AND calculated as if the acids were alone and not in a mixture.
July 16, 2016

Chemistry
Look up Ka values. Formic acid is about 10^-4 and HClO is about 10^-8 so formic acid is a much stronger acid. Also there is more of it. I would be tempted to ignore the HClO and calculate pH from HCOOH alone.
July 16, 2016

Chemistry
https://answers.yahoo.com/question/index?qid=20091202141141AAzWAa6 Answers are not in the same order but you get the full explanation here.
July 16, 2016

Chemistry
Do you have thoughts on this? It seems obvious to me that delta H is +. NH4NO3(s) + H2O ==> NH4NO3(aq) - heat
July 16, 2016

chemistry
We can't draw on this forum but here is a link that shows a diagram. https://www.google.com/search?q=activation+energy&ie=utf-8&oe=utf-8 The graph is a potential energy diagram. The X line shows the energy at the start, the Y line shows the energy at the end and the space ...
July 16, 2016

Chemistry HELP!!!
How many mols of each do you have? mols = grams/molar mass A is 4/4 = 1 mol B is 4/32 = 0.125 mol C is 4/2 = 2 mol D is 4/18 = 0.222 mol A mole of anything contains 6E23 particles. A is 1 x 6E23 = ? B is 0.125 x 6E23 = ? C is 2 x 6E23 = ? D is 0.222 x 6E23 = ? The one with the...
July 16, 2016

chemistry
When MgCl2 ionizes you get Mg^2+ and 2Cl^-. 2/3 of those ions are Cl^-. What's 2/3 of 6E23.
July 16, 2016

Chemistry
If it's 10 units long then one unit must be 625/10 = 62.5. Look up the four possibilities and see which has a molar mass of 62.5. For example, you know it can't be ethylene. H2C=CH2 is 28. Glucose is C6H12O6 and that is 180 so it can't be that. You can finish.
July 16, 2016

Chemistry
See my response below. Post any questions about my response there. Post your work if you run into trouble.
July 15, 2016

Chemistry
Maybe yes, maybe no. I can't tell exactly what you are asking so here is the problem is greater detail. Step 1 is the equation. Step 2 calculates the mols of what you have (you have 225 g SF6 to prepare) and you get that by mols = grams SF6/molar mass SF6 = 225/146 = 1.54 ...
July 15, 2016

Chemistry
1.54 mols for 225 g SF6 is correct. Go to the head of the class.
July 15, 2016

Chemistry
This a regular stoichiometry problem. Here are the steps; I suggest you print this out and keep it. This procedure will work any "simple" stoichiometry problem. It will work limiting reagent problems, also, but it needs two or three extra steps thrown in. 1. Writ and...
July 15, 2016

chemistry
mL1 x M1 = mL2 x M2 250 mL x 0.30M = mL2 x 0.10
July 15, 2016

chemisrty
e. I'll bet you could google, solubility PbO and find the answer quicker than waiting on someone to answer here..
July 15, 2016

Chemistry
How much O2 and N2 are you starting with?
July 15, 2016

Chemistry (DUE TONIGHT)
Thanks for all of the information but it would have helped if you had shown how you obtained the 1.27 number. I used this 97900 = 8.314*780*lnK and obtained approx 4E6.
July 15, 2016

chemistry practical
I don't understand the question.
July 15, 2016

chemistary
Please rephrase the question. It makes no sense as is. I would read that as 2 mol sulfur trioxide but that may not be what you have in mind.
July 15, 2016

chemistry
This is a limiting reagent (LR) problem. CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 mols CaCO3 = grams/molar mass = ? mols HCl = grams/molar mass = ? Convert mols CaCO3 to mols CO2 Convert mols HCl to mols CO2 You will see that the mols CO2 don't agree; the correct answer in LR...
July 15, 2016

chemistry
"Structure" of bonding? The Cu to acetate part is essentially ionic, the bonds in the acetate are essentially covalent.
July 15, 2016

Science-light
If the arrangement is correct you really don't need a dark room; however, I assume the arrangement was not right. In this case, the light from the room would be measured and that isn't what you want.
July 14, 2016

college chemistry
How much do you want to prepare. I decide that first the I work these. You can decide later if you work it by molarity first. My way here. Let's say you want 1 L, then millimols = mL x M = 1000 mL x 0.2M = 20 mmols. pH = pK2 + log (base)/(acid) 5.7 = 7.2 + log b/a b/a...
July 14, 2016

@Steve--Chemistry
I don't think so. I answered the same way for Mariah about a week ago. The problem may be a faulty one OR she is not posting the numbers correctly.
July 14, 2016

Chemistry
Na2CO3 + 2HCl ==> 2NaCl + 2H2O + CO2 grams Na2CO3 actually titrated is 1.06 x (10/250) x 2(25/500) = ? mols Na2CO3 titrated = ?g/molar mass Na2CO3. mols HCl used = 2*mols Na2CO3 Then M = mols HCl/L HCl = ?
July 14, 2016

Chemistry
Its polar character.
July 14, 2016

Chemistry
They have different attractive abilities to the solvent used in the separation.
July 14, 2016

Chemistry
You're making it much too hard. How mcuh is rate increased when NO is doubled? That's rate = k[NO]^2[H2]. When NO is doubled rate is 4x; i.e., 2^2 = 4. When tripled rate is 9x; i.e., 3^2 = 9. What's the ratio of 9/4?
July 13, 2016

chemistry
CH4 + 2O2 ==> CO2 + 2H2O dHrxn = (n*dHo products) - (n*dHo reactants). Look up the dHo formation in your text, notes, net, and calculate.
July 13, 2016

Chemistry
Can you help. I don't know what the hubber process is? There is a Haber process for making ammonia but why would you test for ammonium. For that matter, what is ammonium?
July 13, 2016

Chemistry
July 13, 2016

Chemistry
How many mols do you need? That's mols = M x L = ? The mols = grams/molar mass. You know mols and molar mass, solve for grams.
July 13, 2016

Chemistry
a. Actually, no one knows; however, if all 4.80 dm^3 reacted AND the Cl2 gas was at STP, then it is 4.80/22.4 = ? b. Can't answer b,c,d. Is NaOH concd or dilute? Is it hot or cold? Here are a couple of reactions but there are others. 2 NaOH (conc., cold) + Cl2 = NaClO + ...
July 12, 2016

Chemistry
CuSO4 + Na2CO3 ==> CuCO3 + Na2SO4 mols CuSO4 = 1.5 mols CuCO3 = 1.5 x (1 mol CuCO3/1 mol CuSO4) = 1.5 grams CuCO3 = mols CuCO3 x molar mass CuCO3.
July 12, 2016

Chemistry
There is no reaction. There is a shift in the solubility equilibrium of Mg(OH)2 but no reaction.
July 11, 2016

Chemistry
pH = -log(H^+). pH 2.4; (H^+) = 3.98E-3 pH 4.4 = 3.98E-5 So it has been diluted by 100 times. 3.98E-3 x (10 mL/x mL) = 3.98E-5 Solve for X. You should have gone to 1000 mL. By the way, you should use the same screen name. We can help you better if you do.
July 11, 2016

Chemistry
This is a limiting reagent (LR) problem. I work these the long way but I think it's easier to explain this way. C + O2 ==> CO2 mols C = grams/molar mass = 14/12 = approx 1.1 but you need to redo this for a more accurate number. mols O2 = 58/32 = 1.8 Convert mols C to ...
July 11, 2016

Chemistry
I could just give you a formula that will do this; I memorized it years ago but here is a question by question approach. What is the definition of molarity. M = mols/L. So that's what we need to determine. How much does a L weigh? That's 1.114 g/mL x 1000 mL = 1114 ...
July 11, 2016

Chemistry
coulombs = amperes x seconds C = 3.00 x 48hr x (60 min/hr) x (60 s/min) = approx 518,000 C but you need to do that more accurately. We know that 96,485 coulombs will use 1 equivalent of Cu (1 eq of Cu is 63.54/2 = approx 32 g). So how much Cu is used? That's approx (63.54/...
July 11, 2016

Chemistry
This is done the same way as the Cu post I did for you above.
July 11, 2016

chemistry
What is your trouble with this one. EXACTLY what do you not understand. We HELP work problems but I don't see any work on your part.
July 11, 2016

chemistry
What do you think and why?
July 11, 2016

chemistry
Not only do you not get it, you apparently didn't even read how to do the first one.
July 11, 2016

chemistry
I'll be glad to help you through it BUT you must tell me what you don't understand about the problem and where you're having trouble. We HELP do homework.
July 11, 2016

chemistry
Isn't this just another LR problem? What are you having trouble with?
July 11, 2016

chemistry
Note that I showed how to do it in mols AND in grams.
July 11, 2016

chemistry
NaHCO3 + HCl ==> NaCl + H2O + CO2 mols NaHCO3 = grams/molar mass = 20/84 = approx 0.24. mols CO2 formed if NaHCO3 is the limiting reagent (LR)is 0.24 mols NaHCO3 x (1 mol CO2/1 mol NaHCO3) = 0.24 mols CO2. mols HCl = 22/35.5 = approx 0.62. mols CO2 formed if HCl is the LR ...
July 11, 2016

more dump---chemistry
Question 8 is the same kind as the first one you posted. Work it the same way. For the others, posting multiple questions with one posts USUALLY results in nothing being answered because it takes too much time for a single post. You might consider posting these as single posts...
July 11, 2016

Homework dump---chemistry
When magnesium metal and an aqueous solution of hydrochloric acid combine, they produce an aqueous solution of magnesium chloride and hydrogen gas. Using the equation, Mg (s) + 2HCl (aq) Imported Asset MgCl2 (aq) + H2 (g), if 72.9 g of Mg and 146.0 g of HCl are allowed to ...
July 11, 2016

@DrRebel----chemistry
No. Qc = 0.12; Kc = 0.8 Qc < Kc (or in your language Kc > Qc). Therefore, to make Qc = Kc requires products to increase and reactant to decrease. If you try shifting the reaction the other way you get a negative number for x and that can't be. Try working the problem...
July 10, 2016

chemistry
First you must determine which way the reaction will shift to react equilibrium. That is done with Qc. Qc = (PCl3)(Cl2)/(PCl5) = 0.12*0.12/0.12 = 0.12= Qc and Kc = 0.8 so Qc is too small which means products are too low and reactant is too high so shift must be from left to ...
July 10, 2016

chemistry
Do you mean with "final concentration" you want composition of NH3 or do you want the dissociation components; i.e., NH4^+ and OH^-. I will assume you want final NH3 composition and not the dissociation parts. mols #1 = M x L = ? mols #2 = M x L = ? final (NH3) = ...
July 10, 2016

Chemistry
You need to understand what's happening here. You add an excess of HCl to CaCO3 and it reacts completely but not all of the HCl is used. The NaOH is to determine how much of the HCl excess is there after all of the CaCO3 is gone. CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 ...
July 10, 2016