Thursday
April 24, 2014

Posts by DrBob222


Total # Posts: 41,920

Chemistry
Substitute the numbers into the Henderson-Hasselbalch equation and calculate the ratio of (base)/(acid). That will tell you whatever you need to know about the ratio.

Chemistry
If you know H^+ or OH^- the other can be calculated from (H^+)(OH^-) = Kw = 1E-14 If you want pH pH = -log(H^+) If you want pOH pOH = -log(OH^-) If yo have pH or pOH and want the other one pH + pOH = pKw = 14

chem
See your post above.

Chemistry
See your posts above.

Chemistery
Use PV = nRT

chemistry
The first two are right. Silver ION is Ag^+. Ag is silver metal. Plumbous bromite is Pb(BrO2)2 Plumbous makes it +2 valence instead of +4. Bromite is BrO2^- I might be able to help with the first part of your question if I knew what the problem is.

Chemistry
Pb(NO3)2 + Na2SO4 ==> Divide this into Pb(NO3) is Pb + element; NO3^- - element. Na2SO4 is Na + element; SO4^2- l element. + of #1 goes with - of #2 + of #2 goes with - of #1. (Actually, I think that's the hard way to do it; you just change partners between the two comp...

Chemistry check and help
See your post above.

Chemistry
delta x (position) = h/4*pi*mdeltav. delta x = h you know 4*pi you know mass = 247 lb converted to kg. delta v is 17.09 x 0.1 m/hr conerted to m/s. Here is a site that does a pretty good job of explaining how to do this. I've also included another site that helps, too. htt...

Chemistry
You do them step by step. I use units I have memorized; sometimes that means going around the house more times to get where I'm going but it keeps me from memorizing a book of conversion factors. 3.50 mi/hr to yards/min. I remember there are 5,280 feet/mi There are 3 feet/...

chemistry
You need to rephrase this question. You have CuSO4.5H2O produced but it is a reactant. And I don't see where you have any glycine at all.

chemistry
Plot the data as pH on the y axis and mL on the x axis. Locate the equivalence point, read the mL, divide that by 2 and read the pH at that mL mark (the mL/2 mark that is) and that will be the pKa value for the weak acid.

chemistry
q = mass Pt x specific heat Pt x (Tfinal-Tinitial) 20.7 = 11.0 x sp.h. x (35.8 - 20.5) sp.h. = ?

Chemistry
8N2O4 + S8 + 8H2O ==> 8H2SO3 + 16NO

Chemistry: Freezing point depression
mols EtOH = grams/molar mass m = mols EtOH/kg solvent delta T = Kf*m Subract delta T from zero to find nw freezing point.

chemistry
I think 1 is right. I disagree with 2. Yes, the solution of NaOH M is too low since all of the NaOH has not dissolved but during the second titration the NaOH is stronger which means it takes less NaOH than it should and M = mmols/mL so smaller NaOH mL means a larger M. 3. The...

khumbula high school
Isn't this a personal question; i.e., one for you to answer? Your prof doesn't want to know the study fields and preferences for volunteers on this site.

Chemistry
2.5 mol Al2(SO4) x [3 mol S/1 mol Al2(SO4)3]= ?

incomplete---science

AP Chemistry
Yes, the answer is b. mols BZth = grams/molar mass = ? mols benzene = grams/molar mass = ? Xbenzene = mols benzene/total mols. Then pbenzene soln = Xbenzene*Pbenzene where Pbenzene is 93.4 mm = normal vapor pressure.

Chem
It's pKa whatever that is. Do you have a Ka for HA?

Chem
mmols HA = 565 x 0.25M = 141.25 mmols NaOH = 500 x 0.160 = 80 ........HA + OH^- ==> A^- + H2O I......141.25..0......0.......0 add..........80................. C.......-80.-80.......+80 E........?....0.......80........ Substitute the E line into the Henderson-Hasselbalch equ...

Chemistry ASAP
M = mols/L solution

chemistry
I can't imagine what this is.

chemistry
c is the highest a is the lowest

Chemistry
The E value differs for acid vs basic solution. Look in the reduction potential table for these two values.I don't remember them off hand but I think 0.82 sounds familiar.

chemistry
mols solute = grams/molar mass Then M = mols/L solution.

chemistry
Kp = Kc(RT)^delta n.

1 question!
I would go with c.

science
(P1V1/T1) = (P2V2/T2) Remember T must be in kelvin

Chemistry - Le Chatelier's Principle
I don't know what it is you don't understand. Frankly you seem to understand it very well. You add H3O^+ and the rxn shifts to the right producing more dichromate which is what you want. The equation is already there. That is the initial equation, the intermediate equa...

Chemistry
It might change phases from liquid to gas. If you drive off all of the water you would be left with N2O5 which is where HNO3 comes from in the first place. N2O5 + H2O ==> 2HNO3 ==> H2O + N2O5

chemistry
Use PV = nRT and solve for n = number of mols, then n = grams/molar mass. You know n and grams, solve for molar mass.

Chemistry
Note the proper way to write copper(II) sulfate with the cap i and not lower case i. mols CuSO4 = grams/molar mass m = mols/kg solvent. I suppose you are to assume the density of H2O is 1.00 g/mL. Then delta T = i*Kf*m where i for CuSO4 = 2. Finally, subtract delta T from zero...

chemistry
Heat gained by cool water + heat lost by warm water = 0. [mass cool H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass water H2O x specific heat warm H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for T final.

chemistry
Would you believe twice as much as from one mol (and 1 mol is 196.1 kJ IF that is 196.1 kJ for the reaction as written)?

chemistry
I can't decipher the question.

chemistry
d

chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. 1. Write and balance the equation. 2. Convert 150 g KBr to mols. mols = grams/molar mass 3. Convert 120 g Cl2 to mols. 4a. Using the coefficients in the balanced equation, conv...

chemistry
%yield = (actual/theoretical)*100 = 75.5% 0.755 = (50/theoretical). So you want to end up with 66.2g so that with 75.5% yield you will get 50.0 g. You can check that when you finish to see that you actually end up with 50.0 grams. NiCl2.6H2O + 6NH3 ==> Ni(NH3)6Cl2 + 6H2O mo...

CHEMISTRY
Yes, it's endothermic and you're right for the reason, too. The equation tells you that 43.2 kcal is consumed by 1 mol N2 (28g). All you need to do is proportion that out for 50 g. 43.2 kcal x (50/28) = ?

Chemistry
MO + 2HCl ==> MCl2 + H2O How many mols HCl did you start with? That's 0.1L x 1.00M = 0.1 mol. How much was neutralized by NaOH? That's 0.02102L x 0.1020M = 0.02144 but that was for a 25.0 mL aliquot of thae original. So the ORIGINAL amount of HCl neutralized was 0.0...

Chemistry
........2NO + O2 ==> 2NO2 I.....0.775.0.789....0 C.......2x....-x.....2x E..0.775-2x.0.789-x..2x Substitute the E line into Kp expression and solve for x then evaluate the individual pressures. I should point out that I did NOT work this problem as concentrations since you ...

chem
Technically you can't do this without knowing the reaction; however, you probably meant to use both H as in 2NaOH + H2SO4 ==> Na2SO4 + 2H2O So how many equivalents do you want? That's N x L = 0.01N x 0.1L = 0.001 equivalents. Then g = eq x eq wt = 0.001 x 49 = ? You...

chemistry
I think you made a typo for answer D. Are you sure that isn't 0.0106 By the way, instead of solving a cubic equation you can substitute each of the answers into the expression an see which comes out with K of 6250

chemistry
What's the (Cl2) initially. I've used 0 below. ......2NO(g)+ Cl2(g)<-->2NOCl(g) I.....0.1M.....0........1.0M C.....2x +x -2x E.....0.1+2x...x........1-2x Substitute the E line into Kc expression and solve for x. This is a cubic equation.

chemistry
Use PV = nRT and don't forget to change T to kelvin. C + 273 = K.

chemistry
Use PV = nRT for He (n = gram/molar mass) and solve for pHe. Do the same for Ne, then add the partial pressures to obtain total pressure. #2 use PV = nRT

College Chemistry
A four step procedure will work these problems. 1. Write and balance the equation. You have that. 2. Convert what you have (in this case 81.0 g Na) to mols. mol = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols of what you have (Na) to mol...

CHEMISTRY
6.724g hydrate -2.964g anhdrous Na2SO4 ---------- 3.760g H2O driven off. Convert to mols. 3.760/18 = ? mols H2O 2.964/molar mass Na2SO4= ? Now find the ratio of the water to 1.00 mol Na2SO4.

CHEMISTRY
Convert 6.50 g N to g urea. 6.50 g N x (molar mass urea/2*atomic mass N) = ? g urea.

chemistry
q1 to melt ice solid to liquid water at zero C. . q1 = mass ice x heat fusion q2 to warm liquid water from zero to 45 C. q21 = mass H2O x specific heat H2O x (T final-T initial) Total = q1 + q2

chemistry
tritium

Chem
(P1V1/T1) = (P2V2/T2)

chemistry
yes A metal will displace any metal ION BELOW it in the activity series. Here is the activity series chart. http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm

chemistry
I thought we did this together about a week ago.

Chem
1/wavelength = R(1/1^2 - 0) Note: that last term is 1/n^2 but if n = infinity then 1/infinity is zero. R = Rydberg constant = 1.0973E7 Solve for wavelength in meters then E =hc/wavelength to solve for energy in joules. You may want to change that to electron volts.

chemistry
If those are partial pressures of each material then the Ptotal = ppentane + phexane

Chemistry
q = mass H2O x specific heat H2O x (T final-T initial)

Chemistry
Someone got happy with the instructions. Verbose I think. And you can't do this with the coefficients? Here is the first one. You have 10.9 mols N2 if I read that table right. You want to know mols N2H4. 10.9 mol N2 x (2 mols N2H4/3 mols N2) \ 10.9 x 2/3 = ? Or from N2 to ...

Chemistry
mols H2 you want. grams/molar mass Convert mols H2 to mols H2SO4 using the coefficients in the balanced equation. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and M, solve for L and convert to mL if desired.

chemistry-urgent
I took a year of course work to identify cations and anions and you want me to condense all of that into a short answer here? Ha! and LOL. Cl^- is the anion present. The best thing you can do is know reactions of anions and cations and the solubility rules. Thos two will take ...

Chemistry
2H3C6H5O7 + 9O2 ==> 12CO2 + 8H2O mols citric acid = grams/molar mass Convert mols citric acid to mols CO2 using the coefficients in the balanced equation. That/s ?mols citric acid x (12 mols CO2/2 mol cit acid) = ? Now convert mols CO2 to grams. g = mols x molar mass.BTW th...

Chemistry
See your other post.

Chemistry
See your other posts.

Chemistry
I don't see a P1V1 = P2V2. I see a (P1V1/T1) = (P2V2/T2) so the T is taken into account.

Chemistry
Damon used PV = nRT. n isn't known at the conditions listed. Using those conditions allows the evaluation of n. Then that value of n is used in another PV = nRT calculation to solve for the volume at the new conditions. You can avoid that problem if you use (P1V1/T1) = (P2...

AP Chemistry
See your post below. 100 C p = 760 torr

AP Chemistry
Use the Clausius-Clapeyron equation. One piece of information you must know is that at the boiling point of benzene the vapor pressure is 760 mm.

Chemistry
dHfreaction = (n*dHf products) - (n*dH products) Look up the numbers ad calculate.

chemistry
copper? carbon?

chemistry
I did this in my head and I BELIEVE (but you need to try it to see) eqn 3 reversed. Add to 2x eqn 1 and add to the reverse of 2 x equn 2. Add the dH values. When you multiply a rxn by a coefficient do the same for dH. When you reverse and equation change the sign on dH.

chemistry
I think I've answered this before. H2O(l) ==> H2O(steam) Convert kg to mols H2O at 25 and calculate the volume occupied. Do the same for volume at 133 C using PV = nRT. w = -p*delta V.

chemistry
Qv = Ccal x specific heat That gives you Qv/0.01607 mol. Convert to 1 mol Add the appropriate sign. T increased meaning heat was emitted meaning dH is - and exothermic.

chemistry
The difference is 62.6-48.4 = 14.2 So the closed end is higher pressure than the open end so 758-14.2 = P closed end.

chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. 2CuS + 3O2 ==> 2CuO + 2SO2 mols CuS = grams/molar mass mols O2 = grams/molar mass Using the coefficients in the balanced equation, convert mols CuS to mols CuO. Do the same ...

chemistry
Na2SO4(aq) + Pb(NO3)2(aq) ==> PbSO4(s) + 2NaNO3(aq) SO4^2-(aq) + Pb^2+(aq) ==> PbSO4(s)

chemestry
B = 2 C = 3 O = 3*3 = 9 total 2 + 3 + 9 = ?

Chemistry
mols Cu = 139,000/atomic mass Cu = ? Then there are 6.02E23 atoms in 1 mol.

Chemistry
For Fe2O3. (2*atomic mass Fe/molar mass Fe2O3)*100 = ? The others are done the same way.

chemistry
mols KCl = grams/molar mass = ? mols CaCl2 = M x L = ? mols K^+ = mols KCl mols Ca^2+ = mols CaCl2 mols Cl^- = mols KCl + 2*mols CaCl2 Then (K^+) = mols K/L (Ca^2+) = mols Ca/L (Cl^-) = mols Cl/L Note: total volume is 81 mL + 28 mL = ? mL and convert to L.

Chemistry
Take a 100 g sample. This gives you 37.51g C. 58.29g O 4.20g H. Convert to mols. mols = grams/molar mass 37.51/12 = approx 3.13 58.29/16 = approx 3.64 4.20/1 = approx 4.20 Now find the ratio of the elements to each other with the smallest whole number being 1.00. The easy way ...

analytical chemistry
Yes but you didn't multiply right. (rather, I think you transposed the numbers)

Chemistry
Do you mean 0.5M. M means molar. m means molal. pH = pKa + log (base)/(acid) 6.8 = 0.127 + log (0.5M/x) Sovle for x.

Chemistry
I worked this for you last night.

Chemistry
mols = M x L = ?

Chemistry
0.01 mol PbCl2 is dissolved. +0.08 mol LiCl. Total Cl = 0.08 + 2*0.01) = 0.1 mol Cl Then Kquotient = (Pb^2+)(Cl^-)^2 = (0.01)(0.1)^2 = 1E-4. Is that greater or less than Ksp? If greater, yes a ppt will occur. If less no it will not occur.

Science... plz help~!
Those look ok to me.

chemistry
6% (is that w/w ?) means 6g NiSO4 in 100 g solution. That is 6g NiSO4/(6g NiSO4 + 94 g H2O). So 200 g sample would contain twice those amounts.

Chemistry
My recommendation is to Google "properties acids & bases".

chemistry
Isn't Charles' Law all about volume and temperature and they are directly proportional? T goes up; V goes up.

chemistry 1
Sparse information. grams/molar mass = mols M x L = mols

Chemistry
No, A uses pK2 not pK3. And I think it is pK2 + log (BASE/ACID) but H2PO4 is the acid and HPO4 is the base. I calculate approx 8.1 but you should be more careful. We'll take your values as ok. 0.7256 mol base 0.1 mol acid So in 20 mL you will have 0.145 mol base and 0.02 m...

Chemistry
Google this.

Chemistry
15M x (25.0 mL/125 mL) = ? Or you're diluting it by a factor of 5 and 15/5 = ?

Chemistry
See your other post.

Chemistry
Use the dilution formula of c1v1 = c2v2 18M*vmL = 6M*250mL v = ?mL.

chemistry 2
You want 800 x 0.69 = approx (you need to do it) 552 mmols total. I may have different K values than you. I will use 7.20 for pK2. 7.6 = 7.2 + log (base)/(acid) Solve for b/a and I get approx b/a = 2.5 (in millimols--not concn) a + b = 552 (in millimols). Solve these two equat...

College Chemistry.
Reverse eqn 1 and add to 3x eqn 2. That gives you the equation you want. Then for dH, change the sign of eqn 1 and add to 3x dH for eqn 2. By the way, you can't get what you want UNLESS you balance that equation you want. 2H2S + 3O2 ==> 2SO2 + 2H2O

Chemistry
m = 4 mol/kg = 4 delta T = Kb*m

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