Saturday
February 6, 2016

# Posts by DrBob222

Total # Posts: 51,308

Chemistry
%H = 0.290/78.9*100 = ? %N = 4.06/78.9*100 = ? %C = 100-%H-%N = ? Then mass C in 3.37 g sample HCN = 3.37 x (%C/100) = ?
September 6, 2015

chemistry
You need to clarify what you did. I have no idea what you're talking about.
September 6, 2015

chemistry
(rate 1/rate 2) = sqrt(M2/M1) where M2 and M1 are molar masses. Make up a number for the "certain volume". I would use a convenient number like 100 L. Then rate1 for oxygen = 100 L/20 = 5 L/s rate 2 = ? M2 = 2 for H M1 = 32 for O Substitute into the above and solve ...
September 6, 2015

sita college
I posted the answer to this elsewhere. If you can't find it let me know and I'll give you a link.
September 6, 2015

Chemistry
I'm not sure why you're having trouble. The question WRITES the word equation for you. sulfuric acid + heat gives sulfur trioxide and water. reactants on left; products on right. H2SO4 + heat ==> SO3 + H2O. I cant writ eh heat sign over the arrow but that's the ...
September 6, 2015

Chem
Frankly, I don't think the problem is written very well; however, I think you need to reread the problem. It says, "The methanol burns completely...." which tells me that all 200 g burned. I don't know how to answer A. The gases will have some heat energy and...
September 6, 2015

Chemistry
It a different kind of question which I've never seen before and it's a little tough. A chemical reaction involves either a decomposition of one material to different materials or a combination of one material with another. This process is a chemical reaction and in ...
September 6, 2015

organic chemistry
I don't know that I would say MUCH more volatile. That depends upon what two or three alkenes/alkadienes you are comparing. Also it may depend more upon the intermolecular forces than on the number of pi bonds.
September 6, 2015

organic chemistry
I would agree with you but I would say it contains ONLY 1 double bond.
September 6, 2015

Chemistry HELP
wavelength = h/mv
September 5, 2015

Chemistry
I did a quickie. I didn't get that. wavelength = w frequency = f w = h/mv and c = f*w Then from c = f*w we get w = c/f c/f = h/mv cmv = hf f = cmv/h f = 3E8*9.11E-31*1.85E7/6.626E-34 = ?
September 5, 2015

Chemistry
wavelength = h/mv, then c = wavelength*frequncy
September 5, 2015

chemistry
You want to recover the salt or the ethanol. Evaporate the ethanol to recover the salt.
September 4, 2015

Chemistry
volume Pb cube = 1.8^3 = ? volume Al cube = 1.8*3 = ? The water level in the graduated cylinders will rise. The new water level in each beaker will be the old water level + the volume occupied by each metal.
September 4, 2015

Chemistry
I answered this earlier. Instead of post again if you don't understand, state what you don't understand and what is giving you trouble. I left you with an equation and there is only ONE way density can get smaller if the mass is constant. http://www.jiskha.com/display....
September 4, 2015

Chemistry
density = mass/volume mass stays the same. So for density to get smaller what must happen to the volume?
September 4, 2015

Chem
0.07M is 0.07 mols/L solution mols = g/atomic mass 0.07 = g/19 so g F^- = approx 1.33 g/L solution or 0.133 g/100 mL solution = 0.133 g/100 g solution. mass% = g F^-/100 g solution. ppm = mass% x (1E6/1E2) = 1E4 x mass% 1
September 4, 2015

chemistry
mass = volume x density
September 4, 2015

chemistry
area square piece = 4.8 in*2.54 cm/in x 4.8 in x 2.54 cm/in = ? cm^2 and mass = 1.5 g area large piece = 27.73 cm x 21.50 cm = ? cm^2 mass 1 sheet large paper = 1.5 g x (area large sheet/area small sheet) = ? g x 500 for 500 sheets paper. mass 500 sheets/454 = lbs for 500 ...
September 4, 2015

oops--Chemistry
Note that I started with there is no correct answer but show the correct answer as D. I just didn't go back and remove that first sentence.
September 4, 2015

Chemistry
There are no correct answers listed. If n = 4, then l may be 3,2,1,0 so a is out. b,c,d are allowed from n alone. Look at b. If l = 2, then m(l) may be -2,-1,0,1,2 so b is out since m(l) of 3 is not allowed. c is out for the reason you point out. Check out d. n of 4 allows l...
September 4, 2015

chemistry
For O2 I would have rounded 0.285 to 0.28 and I think both should have a - sign. Personally, I think the words "rate of disappearance" should take care of the negative sign but sometimes that isn't so.
September 4, 2015

chemistry
k = 0.693/t1/2 Substitute k into the below equation. ln(No/N) = kt No = The problem doesn't say how much to start with so start with 100 grams. N = what you end up with after 60 days. k from above. t = 60 days Starting with 100 g will give you a fraction and that x 100 ...
September 3, 2015

Thermodynamics
q = mass Cu x specific heat Cu x (Tfinal-Tinitial) Watch the units. I would use J for q, g for mass and specific unit (you will need to look that up in your text or notes) in units of J/g*C
September 3, 2015

Chemistry
dG = dH - TdS Watch the units between dH, dG, and dS. Also T must be in kelvin.
September 3, 2015

chem
No. H2O is a compound as is NaCl (tble salt). Air is a mixture. Salt water is hard to say since I don't know enough about the source. If you dissolve NaCl in H2O you get a solution; if you do this in ocean water it may be a mixture because there are solid particles in ...
September 3, 2015

entrepreneurship 1
This is all about you and not about me. I'm retired but if I were younger, I would have started a business in chemical analysis and consulting (since I'm a chemist). Those services were not available in the town where I lived but two things kept me away from that. One ...
September 3, 2015

Chemistry
Remember this. It will do it all. n = principle quantum number. May take any whole number beginning with 1. l = azimuthal quantum number. May be any whole number beginning with 0 with a maximum of n-1. m(l) = magnetic quantum number. May take any whole value from -l(ell) to +l...
September 3, 2015

Chemistry
I assume this star is a sphere. Change the 4.4E26 lb to grams. You know there are 454 g/lb. Change 8.69E5 miles to cm. You know there are 5,280 ft/mi and 12 in/ft and 2.54 cm/in. Radius is 1/2 diameter Volume of a sphere is 4/3*pi*r^3 Then density = g/cc Post your work if you ...
September 3, 2015

Chemistry
HCN(l) + H2O(l) ==> H3O^+(aq) + CN^-(aq)
September 3, 2015

Chemistry
September 2, 2015

chemistry
molar mass KOH is 56.1 for starters and 2.00/56.1 = 0.0357 M KOH = 0.0357/0.250 = 0.143 instead of your number of 14. H2SO4 + 2KOH ==> K2SO4 + + 2H2O mols H2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols KOH. Then M KOH = mols ...
September 2, 2015

Chemistry
https://nces.ed.gov/nceskids/help/user_guide/graph/variables.asp
September 2, 2015

Chemistry
I don't know if this is a trick question or not. Your reasoning is sound in that acetic acid is more polar than ethanol; however, both acetic acid and ethanol are miscible with water. Miscible means that the material dissolves in water in all proportions so the question is...
September 2, 2015

Science-AP Chem
Yes, but you need one more conversion factor. You need 1 fluid oz = ? mL. That answer is 29.57 mL 29.57 ml/1 fl oz) x (0.5 fl oz/tbsp) x (1 tbsp/3 tsp) = about 4.93 mL
September 2, 2015

Chem
3 and 4 are correct. 1 and 2 are not. #1. First I don't know what the balance at the far side of the room is; however, that is beside the point. It is NEVER acceptable to write a number anywhere except in your lab manual. After writing it in your lab manual you may then ...
September 2, 2015

Chemistry
What you say is correct and has some to do with the question. I would google to see what color each gas emits in the visible spectrum.
September 2, 2015

Chemistry
Yes but remember the number of electrons makes a difference and where those electrons are placed makes a difference.
September 2, 2015

Chem
Yes, but why did you throw away the other numbers for meters. Why not 1.4224?
September 2, 2015

Chemistry
No. Consider. Actual value = 20.00% Values reported: 20.00% 30.00% 10.00% Avg = (20.00+30.00+10.00)/3 = 20.00 Great accuracy. Lousy precision. In fact with precision like this no one would even report the values; most likely the work will be repeated.
September 2, 2015

Chemistry
No. 0.32 has only two s.f.; therefore, the answer may not have more than two s.f. That 0 in 0.32 is not significant.
September 2, 2015

Chemistry
oxygen dissolved in water - S carbon mixed with sand - M apple juice - S vegetable soup -M sour, curdled milk -M steel -S hydrogen -E salt -E salt is NaCl, a compound distilled water -C ocean water -M depends tap water -S Lake Michigan water -M I guess so uranium -E air -C ...
September 2, 2015

Chem
Either your calculator is giving you a false answer or you aren't reading it right. When I divide 5.896/5 I get 1.1792. You're missing another 1 between 1 and 7. You can always prove what the right answer is by long hand division. Note that your are working the problem...
September 2, 2015

science
Your incomplete question makes no sense to me.
September 2, 2015

Physical science
N2 + 3H2 ==> 2NH3 mols H2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols H2 to mols N2. g N2 = mols N2 x molar mass N2 = ?
September 2, 2015

science
Does it react?
September 2, 2015

chemistry
2HgO ==> 2Hg + O2 mols HgO = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols HgO to mols O2. Then L O2 = mols O2 x 22.4 L/mol = ?
September 2, 2015

Chemistry
I think so.
September 2, 2015

chemistry
No, of course not. #1. sulfite disappearance = 0.458 mol/L*s so 0.458 mol/L*s So3^2- x (1 mol Cl^-/3 mols So3^3-) = ? So #2 must be what. Make those units cancel to come up with the unit you want.
September 1, 2015

chemistry
It works the same way as stoichiometry. 1. 0.458 x 1/3 = ? 2. Same process as in #1.
September 1, 2015

Chemistry
First, I will assume you meant 1.5 M and 2.0 M. M stands for molarity, m stands for molality. Second, this is a limiting reagent problem and you know that because amounts are given for BOTH reactants. 3NaOH + H3PO4 ==> Na3PO4 + 3H2O mols NaOH = M x L = ? mols H3PO4 = M x L...
September 1, 2015

Chem
Amy, I'm at a loss. Both Damon and I showed you how to work this problem. Somehow you punched in the wrong numbers or punched a wrong button on the calculator. The easiest way, short of me working the problem for you (which doesn't help you) is for you to show each ...
September 1, 2015

Chem
The problem says equal masses so make up a number, say 10 grams. Then mass = volume x density or v = mass/density. Using the 10 g and density of each, calculate volume of each. That will be the volume occupied by the 10 g sample of each. The largest volume will displace the ...
September 1, 2015

Chem
No. You must have punched a wrong key somewhere.
September 1, 2015

Chem
I think you must be overthinking this problem. 11.229 g = mass HCl + empty beaker -5.333 g = mass empty beaker -------------------- ?? = mass HCl Then density HCl = mass HCl/volume HCl. The mass is given in the problem.
September 1, 2015

Chemistry
mols AgNO3 = grams/molar mass Then M = mols/L solution. Technically this problem can't be worked because the definition is mols/L SOLUTION and when you put 5.0 g AgNO3 in 25.0 mL water that DOESN'T make 25.0 mL solution but the solution volume is slight more than 25.0 ...
September 1, 2015

Chemistry
There are at least two reasons why the wood flame is yellow. One is that the temperature of the burning wood is not high enough to completely burn some of the materials in the wood and you are seeing the "luminous" flame from the carbon that hasn't burned. The ...
September 1, 2015

Chemistry
You are so very correct. Good work.
September 1, 2015

Chemistry
The luminous flame is caused by the gas not burning completely. The "luminous" part is caused by the glowing embers of the carbon that wasn't burned to CO2. So you think the answer is ......?
September 1, 2015

Decimals
I would say one point two zero two but I don't think that's what you mean. Another way is to say one and two hundred two thousandths.
September 1, 2015

Chemistry
I didn't think to post the earlier but since you have so many significant figures in the wavelength calculation, you could use that many places in the speed of light. I don't know that many places but I know it's available on the web.
September 1, 2015

Chemistry
Looks ok to me.
September 1, 2015

Chemistry
No. 1,650,763.73 is not the wavelength. Look at my first response again. 1 m = 1,650,763.73 x wavelength and you calculate the wavelength from that. Frequency is in the order of 10^14 Hz unless I punched te wrong buttons.
September 1, 2015

Chemistry
Not what I get. What is the wavelength you have. Post your work and I'll find the error.
September 1, 2015

Chemistry
What is the wavelength of the Kr line? That is 1 m = 1,650,763.73 x wavelength. Solve for wavelength. Then c = freq*wavelength wavelength is from above. c = 3E8 m/s Solve for freq. Obviously if it is an orange-red line it must be in the visible part of the spectrum. By the way...
September 1, 2015

Chemistry
I found a couple of sites that talk about photosynthesis being a reversible reaction. The idea in both sites is that the reaction in which plants produce O2 is essentially reversed when humans/other animals produce CO2; however, this is not the same thing as a reversible ...
September 1, 2015

Science
I have time to be here and I'm here almost all the time. I'm sorry I answered a test question for you. Tests are meant to test your knowledge, not mine. I wasn't complaining at you or to you; I just wanted you to think.
September 1, 2015

Science
Don't be impatient. It takes time for us to respond. See your post below. By the way, it would not have hurt anything for you to have put some thought into this. As it is I'm doing the thinking and the idea behind this type of question is for you to think.
September 1, 2015

Chem
Your post makes no sense but I suspect you are looking for the word "atom".
September 1, 2015

Science
You are in your house and you need to lift a 500 lb piece of equipment that is resting on the floor to a shelf that is about 4 feet high. You have no help at home. You want it moved now. How can you do it? Answer: Get a solid board long enough to form an inclined plane from ...
September 1, 2015

Chem
Did you intend, I assume so, to write calorie with a capital C? That stands for 2700 kcal. 1 calorie = 4.184 joules. 1 kJ = 1000 J. 2700 kcal x 1000 = 2,700,000 cal. 2,700,000 cal x * (4.184 J/cal) x (1 kJ/1000 J)
August 31, 2015

Chemistry
density = mass/volume. mass = 2.3504 from the problem. volume = 35.2-33.5 = ?
August 31, 2015

Chemistry
http://www.jiskha.com/display.cgi?id=1440990124
August 31, 2015

oops typo--Chemistry
That 1/n^3 sub 2 should be 1/n^2 sub 2
August 31, 2015

Chemistry
dE = 2.18E-18(1/x^2 - 1/y^2) Where x = 2 and y = 3 or x = 2 and y = 4. It's hard to write the formula on this forum which is why I used x and y; here is a try at the equation. dE = 2.18E-18(1/n21 - 1/n32 where n1 is < n2
August 31, 2015

Chem
No. 2.60E22/6.022E23 = 0.0432 Did you punch in those numbers on your calculator? The digits are right; the exponent is not. 10^22/10^23 = 10^-1 or 0.1
August 31, 2015

Chem
1 mole is anything is 6.022E23 so 2.60E22 atoms Ag x (1 mol Ag/6.022E23) =?
August 31, 2015

biochemistry
millimols HAc = 325 x 0.11 = about 36 but you need to do it more accurately. ........HAc + NaOH ==> NaAc + H2O I.......36.....0........0 add............x........... C.......-x....-x........+x E......36-x....0........+x Redo so you have good numbers for the E line, then ...
August 31, 2015

Physical Chemistry
3% what? w/v. That's what I will assume. 3% w/v means 3 g H2O2 per 100 mL solution. 2H2O2 ==> 2H2O + O2 In the 5.00 mL you will have 3g x (5/100) = ? g H2O2 Convert to mols; mols = grams/molar mass = ? Using the coefficients in the balanced equation convert mols H2O2 to...
August 31, 2015

Chemistry
August 31, 2015

Science
Essentially no reaction between sand and acid
August 31, 2015

Science
You are wasting our time and yours. You've posted the same questions, PsyDag answered some of them and I answered one but you continue to post. We've asked that you make it easier for us if you post the answers with the questions. Please don't post any more until ...
August 31, 2015

science
See your post below.
August 31, 2015

Chemistry
mols MgBr2 = grams/molar mass = ? m solution = mols MgBr2/kg solution. Then delta T = i*Kf*m i for MgBr2 = 3 You know Kf and m, solve for delta T, then subtract from zero to find new freezing point.
August 31, 2015

science
1 is correct. Put your answers at the question, not at the end.
August 31, 2015

chem
What are you titrating? Iodine? Surely not the bleach? What's the preparation prior to titration? Do you have an equation for that prep reaction? It may be ClO^- + I^- ==>
August 31, 2015

chemistry
3Ca(OH)2 + 2H3PO4 ==> Ca3(PO4)2 + 6H2O mols H3PO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H3PO4 to mols Ca(OH)2. Now M Ca(OH)2 = mols Ca(OH)2/L Ca(OH)2. You know M and mols, solve for L.
August 31, 2015

Chemistry
Doesn't that mean the electron is ionized? Calculate the energy for an electron moving from n = infinity to n = 1. dE = 2.178E-18(1/1 - 0) dE = 2.178E-18
August 30, 2015

Chemistry
7) 14 carat gold has a purity of 58.3%. How many moles of gold are in 163 grams of 14 carat gold? Answer in units of moles. g Au = 163 x 0.583 = ? mols Au = g/atomic mass = ? 8) A 15.9 g sample of iron ore is treated as follows. The iron in the sample is all converted by a ...
August 30, 2015

chemistry
Pb(NO3)2 + 2KI ==> PbI2 + 2KNO3 Convert each to mols product. The smaller value will be the mols PbI2 produced. 1.37 mols Pb(NO3)2 x [1 mol PbI2/1 mol Pb(NO3)2] = 1.37 mols PbI2 produced. 2.56 mols KI x (1 mol PbI2/2 mols KI) = 1.28 mols PbI2 produced. This is a limiting ...
August 30, 2015

science
delta T = 0-(-.201) = ? delta T = Kf*m You know delta T and Kf, solve for m = molality. m = mols/kg solvent. You know kg solvent and m, solve for mols. mols = grams/molar mass. You know grams and mols, solve for molar mass.
August 30, 2015

Chemistry
Do it as you would for dimensional work. That way you can't fail. 0.3333 mol CO2 x (3 mols atoms CO2/1 mol CO2) x (6.022E23 atoms/mol) = ?
August 30, 2015

Chemistry
The first part of what you did is confusing. Here is what you do. Take 100 g sample which gives you 78.8 g Sn 21.2 g O Convert to mols 78.8/118.71 = about 0.66 21.2/16 = about 1.32 Now find the ratio of the two to each other with the smaller number being no less than 1.00. The...
August 30, 2015

Chemistry
Note the correct spelling of celsius. psoln = Xbenzene*Pobenzene You need Xbenzene. Get that from nbiphenyl = grams/molar mass = ? nbenzene = grams/molar mass = ? Xbenzene = nbenzene/total mols. Then substitute Xbenzene in first equation above and solve for p solution.
August 29, 2015

Science
I think 1-4 are answered correctly although in real life I don't agree with #2; however, that is a personal opinion and your answer is correct. I'm on the fence about the squirrel. Your answer probably is correct but my problem is with the word "about" in ...
August 29, 2015

chemistry
Is there a question here?
August 29, 2015

chemistry
% HCl means grams HCl/100 g solution. 24.8% HCl = 24.8 g HCl/(24.8g HCl + 75.2 g H2O) n HCl = g HCl/molar mass = ? n H2O = g H2O/molar mass = ? XHCl = nHCl/total mols.
August 28, 2015

CHEMISTRY