Wednesday
April 16, 2014

Posts by DrBob222


Total # Posts: 41,733

chemistry
I don't think so.

Science
A. Same results as what? B. Compare the density of two materials; i.e., Al and Au. Al is about 2.7 g/cc and Au is close to 20 g/cc. So th same mass of Al occupies much more space. Why. Because of the spaces between Au atoms are not th same as spaces between Al atoms. C. Some o...

Biochemstry
You don't make sense. base/acid would equal the same as what? base/acid you calculate from pH = pK2 + log (base/acid) and B/A = approx 0.8 and I did that for you which makes base = about 0.8*A You slipped some decimal points. 0.085/0.5L = 0.17 BUT you make sure that 0.085 ...

Biochemstry
KH2PO4 + KOH ==> K2HPO4 + H2O mols KH2PO4 = 11.7/136.08 = about 0.086 Therefore, base + acid = 0.086 (but you need to do it more accurately). 7.10 = 7.21 + log (base)/(acid) B/A = about 0.8 B+A = about 0.086 Solve the two equations simultaneously for B and A. That will give...

CHEMISTRY - SCIENCE
[x g solute/(x g solute + 314 g H2O)]*100 = 42 Solve for x

newton law science
f = ma You know f and you know m, solve for a.

chemistry
heat lost by Fe + heat gained by Au = 0 [mass Fe x specific heat Fe x (Tfinal-Tinitial)] + [mass Au x specific heat Au x (Tfinal-Tinitial)] = 0 Solve for Tfinal.

chem
Just use the dilution formula. mass1 x %1 = mass 2 x %2 Substitute and solve.

Chemistry
0.240g = mss Cu + S compound -0.192g = mass Cu --------------- 0.048 g = S added to the Cu %Cu = (mass Cu/mass total)*100 = ? Take a 100 g sample. mols Cu = grams/atomic mass Cu mols S = grams/atomic mass S Find the ratio of Cu to S with the smaller number being 1.00 Post you...

Science
No. I would go with a; however, it begs the question of "lower than what"? My assumption is lower than fresh water. The freezing point of salt water depends ONLY upon the number of dissolved particles (NaCl, MgCl2, etc.); i.e., how much other stuff is dissolved in it.

Science
If x is doubled it will be 2x. If the price is $4.00 doubling will be $8.00

Chemistry
CuO + H2 ==> Cu + H2O mols CuO = grams/molar mass Using the coefficients in the balanced equation, convert mols CuO to mols Cu. Then g Cu = mols Cu x atomic mass Cu.

Chemistry
You need to find the arrow key on your computer and use it. --> or ==> or >>>>. Using the coefficients in the balanced equation, convert mols each to mols Fe(OH)2. 3.70 mols Fe x (1 mol Fe(OH)2/1 mol Fe) = 3.70 mols Fe. 6.95 mol NiO(OH)2 x (1 mol Fe(OH)2/2 mo...

Chemistry
2KOH(aq)+H2SO4(aq)→K2SO4(aq)+2H2O(l) mols H2SO4 = M x L mols KOH = 2*mols H2SO4 M KOH = mols KOH/L KOH

Chemistry
My vote is with Damon. Ag^+ is silver ion. P^3- is the phosphide ion. For example, Mg3P2 is magnesium phosphide. Mg3N2 is magnesium nitride, etc.

Chemistry
What's a cold alkali? Alkalies are bases and as far as I know there is no difference between a cold one and a hot one other than the rate at which they react.

Chemisty
4Fe + 3O2 ==> 2Fe2O3 mols Fe2O3 = grams/molar mass Using the coefficients in the balanced equation, convert mols Fe2O3 to mols Fe in the equation. You want grams Fe? Convert mols Fe to g. g = mols Fe x atomic mass Fe. Note that the grams 6.52 O2 is not relevant.

Chemistry
5.00 g = initial mass -3.943 g after heating ------- 1.057 g = mass H2O driven off in heating mols H2O = 1.057/18 = about 0.0587 mols CuCl2 = 3.943/134.5 = about 0.0293 Find the ratio and round to whole numbers with the smaller number being 1.00 0.0293/0.0293 = 1.00 0.0587/0....

chemistry
PV/T = k = constant Volume of the tires are essentially constant although they can give a little. Friction between tires and pavement causes heat to be generated. If V is to stay essentially the same, then P must go up if T goes up in order keep k the same. The heavier the loa...

Chemistry
Zn(CN)2 ==> Zn^2+ + 2CN^- .....................+ .....................H^+ .....................v .....................v .....................HCN Note that the added H^+ form HCN with the anion and that forces the solubility equilibrium t the right which increases the solubi...

General Chem
How many mols do you want? That's M x L = ? Then mols = grams/molar mass You know mols and molar mass, solve for grams.

Chemistry
Yes because not all of the lines have the same intensity.

chemistry
See your other posts under other screen names.

chemistry
Show what you can do and explain where you stop and what yu don't understand. I can help you through but you need to get involved other than just posting questions.

chemistry
What do you think and why?

Chemistry
Sara? Jan? Whomever? The ones that ionize 100%.

careers in mathematics and physical sciences
business

Chemistry
mols HClO4 = M x L = ? mols KOH = M x L = ? Subtract. (concn excess acid) or (concn excss base) divided by volume in L = new M. Then pH from that. Post your work if you get stuck.

Chemistry
Al2(SO4)3 + 3BaCl2 ==> 3BaSO4 + 2AlCl3 How many mols BaSO4 were collected? That's 0.760/molar mass BaSO4 = approx 0.0033 but you need to do it more accurately. Using the coefficients in the balanced equation convert mols BaSO4 to mols Al2(SO4)3. Convert mols Al2(SO4)3 t...

chemistry
I'm not sure I understand the "added note". What I have given you at the end is liters CO2 generated by 4.5 gallons of gasoline at 85 F and 30 in Hg. Of course it will displace the atmosphere.

chemistry
1. Write and balance the equation for the combustion of octane. I will do that to get you started. 2C8H18 + 25O2 ==> 16CO2 + 18H2O 2. Look up the density and use that to convert liters gasoline to grams. 3. Convert grams octane to mols. mols = grams/molar mass. 4. Using the...

chemistry
How much of this do you know how to do? Show what you can do and explain where you need help.

Chemistry
a. Take a 100 g sample which gives you 85.63 g C and 14.37 g H. Convert to mols. 85.63/12 = ? 14.37/1 = ? Now find the ratio of C to H with the smaller number being 1.0 and round to whole numbers. This gives you the empirical formula. b. Use PV = nRT and solve for n = number o...

chemistryyyy
You don't remember that (H3O^+)(OH^-) = Kw = 1E-14? You know OH and Kw, solve for H3O^+

Chemistry
Use the Arrhenius equation. The problem gives you k1, make k2 twice that.

Gen.Chem2
Is that m as in molal. m = mols solute/kg solvent Substitute and solve for mol solute. Then mols solute = grams solute/molar mass solute. Substitute and solve for grams solute (NH3)

Chemistry
(V1/T1) = (V2/T2) Don't forget T must be in kelvin

Chemistry
And exactly what is your problem. Do you have the potentials.

chemistry
Look up the Cr and Ni potentials and write the half reaction they represent and we can go through it. It won't help for me to use potentials I look up for our texts may not the same.

Chemistry
good.

Chemistry
Go through the regular steps of a stoichiometry problem; the value get at the end is the theoretical yield. For example, calculate the grams oxygen obtained from the decomposition of 10 grams KClO3. 2KClO3 ==> 2KCl + 3O2 The number of grams O2 obtained will be the theoretic...

Chemistry
k = 0.693/t1/2 Substitute k into the below equation. ln(No/N) = kt No = 100 N = 10 k from above. Solve for t in hours.

chemistry
Ptotal = pH2dry + pH2O You know Ptotal and pH2O, solve for pH2 dry.

Chemistry
I echo Bob Pursley's comment. I have no idea. What experiment are you doing? What does H2O have to do with it? What equation?

College Chemistry
Why do you keep switching screen names? Same question as above. You didn't like the answer you got for the origin of the soot? Accumulation of soot makes the crucible weigh more. right? So how will that affect the mass in the crucible. Fit that into your equations for what...

chemistryyyy
See your follow up post above.

chemistryyyy
Perhaps this will help. Ca(OH)2 ==> Ca^2+ + 2OH^-

Chemistry--acids
1 5 6 7

Chem- Bronsted bases
1 2 4 7

Chemistry
2CuO + C ==> 2Cu + CO2 1. I ignored the CuO because the problem states you want 63.5 g Cu. How many mols Cu is that? mols Cu = grams/atomic mass = 63.5/63.5 = 1 mol Cu is what you want. 2. If it comes from the equation above then 2 mols Cu is obtained for every mol C or 1/2...

Science
2CuO + C==> CO2 + 2Cu Forget the 79.5g CuO. If you want 63.5 g Cu, that is 63.5/63.5 = 1 mol Cu. So you need 1/2 mol C and that is 6 g.

Science
See your other post.

Chemistry
2Al + 3H2SO4 ==> Al2(SO4)2 + 3H2O mols H2SO4 = grams/molar mass Using the coefficients in the balanced equation, convert mols H2SO4 5omols Al2(SO4)3. Now convert mols Al2(SO4)3 to grams. g = mols x molar mass.

Chemistry
I answered this for you earlier. http://www.jiskha.com/display.cgi?id=1393098360

Chemistry - check answers
Those look ok to me.

chemistry
HCN no CO2 yes NO2 probably if you count the resonance structures as being partially multibonding.

chemistry
Why don't you draw the structures and count the electrons? I can't draw the structures on this forum but you can find them on Google.

chemistry
See your other posts. This is too much like doing your homework.

chemistry
You need to know the difference between ionic and covalent compounds.

chemistry
1 could be right in some cases but not always. 2 could be right in some cases but not always. 3 is always correct.

chemistry
This is named hydrogen telluride. If you answered this in my class as dihydrogen telluride I probably would give you credit for it (because it is an unambiguous name) but I don't think that is the IUPAC official name.

chemistry
What's wrong with writing the formula and counting the atoms? GeBr4. I count 5; 1 Ge + 4 Br = 5 atoms/molecule. N2O--3 atoms/molecule N2O5 = ? NS2 = ?

oops--chemistry
In the NH3 example I gave I called that a trigonal planar molecule; I should have named it a trigonal pyramidal molecule.

chemistry
To be polar you must have these TWO items (both of them). Just one won't do. a. You must have polar bonds meaning that the two atoms must have different electronegatives. b. The molecule must NOT be symmetrical (in 3D space). For example, CH4 has polar bonds because the el...

chemistry
See the post just before this one.

chemistry
Subtract to obtain the delta EN. Delta EN of about 1.8 or so is about 50/50.

chemistry
polarity of a bond.

Chemistry
Why can't you look these up in your text notes? Most texts have tables.

chemistry
Look this up on Google. http://en.wikipedia.org/wiki/Hydrogen_sulfide

chemistry
Can you draw the structure? I can't on this forum. https://www.google.com/search?q=structure+AsH3&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb Looks trigonal pyramidal to me.

Chemistry
I agree with 1. The standard curve is too high so readings from it will be too high. 2. It depends upon where the beam is. If the liquid in the cuvette is enough to encounter all of the light beam there will be no effect. If the beam is higher than the top of the liquid, there...

chemistry
P1V1 = P2V2

chem
k = 0.693/t1/2 Substitute k into the below. ln(No/N) = kt No = 100 N = 58.32 K from above. Solve for t in years.

chemistry
q in joules = mass air x specific heat air x (Tfinal-Tinitial) Then 1 J = 2.78E-7 kWh.

chemistry
Go to Google search box and type in "2.9E3 km/hr to inches/second" without the quotation marks and hit the enter button.

chemistry
I don't think the wording means anything else. What else could it mean? Bob Pursley worked this for you yesterday.

Chemistry
How many mols do you need? That's M x L = ? Then convert that to grams. mols = grams/molar mass. You can calculate molar mass and you know mols from above, solve for grams.

college chem
0.6634-0.5745 = 0.0889 M in 0.3964 hrs = about 0.22 M/hr (but you may want to change that to M/s. Then rate change IO3^- x (5 mol I/1 mol IO3) = ? rate change for I^-

chemistry
Ammonia is NH3. 0.750 mols H atoms x (1 mol NH3/3 mol H atoms) = 0.250 mol NH3 Then g NH3 = mols NH3 x molar mass NH3 = 0.250 x 17 = ?

Chem
Why did you plug kJ/mol back into the equation. When you solve it delta H came out in J/mol and it must go back as J/mol. The ln(216/760) is ok but that's all I checked since dHvap wasn't substituted properly. Good luck. It's past my bed time.

Chem
0.8535 is ln (216/92) if I punched in the numbers correctly. 216/92 = 2.348 and ln of that number is 0.85349 which I rounded to 0.8535.

Chem
For the second part use the same equation but I would change the p2:T2 pair to make them the p1:T1 pair, then use the new p2 as 760 (that's the definition of boiling point; i.e., when the vapor pressure of the liquid = atmospheric pressure which of course is 760 mm), then ...

Chem
x will be in J/mol and you must convert to kJ/mol.

Chem
0.8535 = x(2.337E-4)/8.314 0.8535*8.314 = 0.0002337x Solve for x but confirm what I've done.

oops--Chem
I meant Clausius-Clapeyron equation. You have it right and have substituted correctly. Give me a second.

Chem
Use the Arrhenius equation.

oops--Chem 2
I see I spelled anonymous wrong.

Chem 2
no. 0.00346 mols = 1.56g/molar mass molar mass = 1.56/0.00346 =?

To annonymous---Chem 2
nope. That isn't the way math works.

Chem 2
I think I wrote this: delta T = Kf*m Substitute and solve for m = molality m = mols solute/kg solvent Substitute and solve for mols solute. mols = grams/molar mass Substitute and solve for molar mass. I don't think you followed the steps. Take it one step at a time. delta ...

Chem 2
What I meant was that Kf for camphor is 37.7 celsius/m or 37.7 Kelvin/m

Chem 2
You can but it doesn't matter. I think Kf for camphor is about 38 C/m (37.7 maybe?) or something like that.

Chem 2
I think I answered your question. The easy way to find the error is for you to post your work and let me check it. I'm happy to do that for you.

organic chemistry
It hydrolyzes in air, particularly if the air is very humid, to produce CH3COOH (acetic acid which is the vinegar smell).

Chemistry
..........H2SO4 ==> H^+ + HSO4^- I........0.0050M....0......0 C.......-0.005...0.005...0.005 E..........0.....0.005...0.005 So for the first ionization, H^+ = 0.005M and HSO4^- = 0.005M. Then HSO4^- goes through k2. ........HSO4^- ==> H^+ + SO4^2- I.....0.005M....0.005.....

chemistry
What is reaction of medium? NH4^+ + 2H2O + NO2^-==> NH3 + H3O^+ + HNO2 + OH^- and you can combine the H3O^+ and OH^- on the right to form 2H2O, then cancel the 2H2O on the left to leave you with NH4^+ + NO2^- ==> NH3 + HNO2

Chemistry
Google it. Go to Google, type in "3.00E10 cm/s to km/hr" without the quotation marks and hit the enter button.

Chemistry
3.271E-22 g Au/atom x #atoms = 5.00 g. Solve for # atoms.

Chem Check Please!!!
1. Check your data. I don't think the Ka values are correct.I might believe 7.3e-10. And is that 7.3 or 7.4? 2. I don't believe the quadratic formula must be used. 3. Finally,I don't believe the calculation for the quadratic formula.

Chemistry
dm^3 x (10 cm/dm)^3 = ? cc = ?mL

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