Tuesday
July 22, 2014

Posts by DrBob222


Total # Posts: 43,165

college chem
millimols NaOH = mL x m = 17.47 x 0.1 = 1.747 millimols HA = 25 x 0.1 = 2.5 .........HA + NaOH ==> NaA + H2O I........2.5....0.......0......0 added.........1.747............ C......-1.747.-1.747...1.747.....1.747 E......0.753....0......1.747 Substitute into the Henderson-Ha...

Chemistry
mols HCl = grams/molar mass Then M HCl =mols HCl/L HCl M HCl = M (H^+) Then pH = -log(H^+) and pH + pOH = pKw = 14. You know pH and pKw, convert to pOH.

college chemistry
Convert each of the Kb values to pKb = -log Kb and convert those to pKa by pKa + pKb = 14 The closest pKa values to the desired pH is the one you want.

Chemistry
See your other post.

Chemistry
mols CaCl2 = grams/molar mass Then M = mols/L solution

science
You might hypothesize that pyrite (FeS2) burns with coal to produce SO2 as one of the products. SO2 then might dissolve n lakes and streams to produce H2SO3 and that would increase the acidity of the H2O. I would add the equations and balance them.

chemistry
I didn't check any of your calculations. There is no indication of what concentration they want the buffer; therefore, I would assume some convenient (and reasonable) amount of one of the salts, say Na2CO3 = 0.05 mols (which would make the Na2CO3 about 0.5M). That will be ...

chemistry/science
a is ok. b. You have how much in solution. 100 millimols Na2CO3 x (25 mL/250 mL) = 10 200 millimols NaHCO3 x (25/250) = 20 You are adding 20 mL x 0.050M = 1 millimol HCl. .........CO3^2- + H^+ ==> HCO3^- I........10........0.......20 added.............1.............. C........

Chemistry
Yes, fractional orders are allowed.

chemistry
See your other post above.

Chemistry Help Please!!!
#1 you have is close but not right. I would have written for the hydrolysis of NaC2H3O2 as a net ionic equation. CH3COO^- + H2O ==> CH3COOH + OH^- Kb for CH3COO^- = (Kw/Ka for CH3COOH) = about 1E-14/1.8E-5 = ? CO3^2- + HOH ==> HCO3^- + OH^- Kb for CO3^2- = (Kw/K2 for H2C...

science
http://en.wikipedia.org/wiki/Mid-ocean_ridge

science
This question asks for YOUR opinion and why, not my opinion and why.

science
I don't know that it is. Touching it right below is Li and diagonally below is Be.

science
By convection and radiation.

science
It changes speed (and is refracted).

science
Nothing is 100% efficient.

science
We protect outselves from ultraviolet rays from the sun by wearing sunscreen,proper clothing, and sun glasses.

science
Particles with a charge attract oppositely charged particles; magnets attract opposite magnetic fields.

science
I agree.

Science
I would go with d.

Chemistry
heat gained by ice moving from -17 to zero + heat gained by ice melting |+ heat lost by warm water + heat gained by cool water = 0 [mass ice x specific heat solid ice x (Tfinal-Tinitial) + (mass ice x heat fusion at zero C) + [masswarm H2O x specific heat H2O x (Tfinal-Tintial...

chemistry
Let acetic acid (CH3COOH) = HAc ......HAc + KOH ==> KAc + H2O pH = 2.14 so (H^+) = approx 7.2E-3, I think you need the (HAc)= ?

chemistry
See your other post.

chemistry
2 atoms/cell x 22.9898/6.02E23 = mass of unit cell = ? Then mass = volume x density and volume = mass/density = ? a = V^1/34.3E-8 cm but you should go through all of the calculations. This is an estimate as are all of the calculations that follow. For the body centered unit ce...

chemistry
Mg^2+ is twice the charge of Na^+ so the effect is 4x as much. (2^2 = 4) The Mg^2+ ion is smaller than the Na^+ and the closer the ions are togther the tougher it is to pull them apart.

chemistry
ionic charge ionic radius

chemistry
http://en.wikipedia.org/wiki/Effective_nuclear_charge#Calculating_the_effective_nuclear_charge

chemistry
You may be ok by now but all you need to do is to substitute HF and KF. There is no reaction. (KF) = 0.05 x (100/300) = ? (HF) = 0.05 x (200/300) = ? Then HF goes in for the acid concn and KF goes in for the base concn. Actually, there is an easier way to do it I think. Work w...

chemistry
Why not show your work with the HH equation and let me find the error.

college chemistry
millimols BOH = 25 mL x 0.1M = 2.5 millimols HCl = 5.25 mL x 0.1M = 0.515 ..........BOH + HCl ==> BCl + H2O I.........2.5....0.......0......0 added.........0.515............... C......-0.515..-0.515...+0.515 E...... 1.985....0.......0.515 I would substitute the E line into ...

chemistry
I would rank from low to high as N2, HCl, H2O, MgF2 but you should confirm that. Look on Google and check the boiling points.

Chemistry
(NH4)2S ==> 2NH4^+ + S^2- So (NH4)2S = 0.200 That means NH4^+ must be twice that and S^2- is the same as (NH4)2S

chemistry
C'mon. Find the caps key and use it. Oxidation is the loss of electrons. Hint: Fe is zero on the left and +3 on the right. Ag is +1 on the left and zero on the right. so which lost electrons?

physical science
Ozone absorbs most of the UV light from the sun; thus, ozone effectively blocks the UV-B rays from striking the earth.

physical science
To keep UV rays from damaging the skin and eyes.

Chemistry
See this table for ionization energy. http://www.lenntech.com/periodic-chart-elements/ionization-energy.htm

chemistry
Only one because all of the bond lengths are the same. We can't draw the actual structures so we draw several "resonance structures" and all of us understand that the "real" bond structure is an average of all those we have drawn but isn't any one o...

CAN ANYONE HELP?
I'm trying but I can help until I identify the problem. So stick with me and we'll get there. Don't blow by questions away.

Chem
You don't help yourself by changing screen names. I answered this question earlier.

Chemistry help
If dStotal is +, the reaction is spontaneous.

Chemistry help
dH surroundings = -dH/T dStotal = dH surroundings + dH system (in the problem)

Chemistry quick question
No, I'm not going to do your work for you; however, I'll assume that you don't know how to write the formulas. For magnesium chloride. The symbol for magnesium is Mg. The symbol for chloride is Cl. So you look up the valence of Mg and it is +2. If you don't hav...

Chemistry quick question
Do you mean that you don't understand why magnesium chloride is MgCl2 or silver nitrate is AgNO3?

Chemistry quick question
What's the problem here? What do you not understand about these?

Science (chemistry)
I suppose you could do these if you knew how to do the MgCl2, AgNO3 etc.

AP CHEM
There are some rules and that governs weak and strong electrolytes. By definition, a strong acid is one that ionizes 100%. A strong base is one that ionizes 100%. A weak acid or weak base ionize only partially; i.e., less than 100% (such as acetic acid etc). A solute that is c...

Chemistry
I don't know how accurate these are to be but as a first approximation they are as follows: Note that ........H2A ==> H^+ + HA^- and ........HA^- ==> H^+ + A^2- If you calculate H^+ from k1 (both acids) you obtain about 3.16E-4. That comes from k1 = (x)(x)/(0.1-x). S...

Chem- Ideal Gas Law
This is a limiting reagent (LR) problem. CaCO3 + 2HCl ==> H2O + CO2 + CaCl2 mols CaCO3 = grams/molar mass mols CO2 = mols CaCO3 (from the coefficients in the balanced equation). mols HCl = M x L = ? mols CO2 = 1/2 that (do the coefficient thing again.) The values for mols C...

Chemistry 12
side reactions for one.

Chemistry-Gases
2H2 + O2 ==> 2H2O mols H2 = grams/molar mass = about 8 but you need to calculate that as well as all of the other values that follow. mols O2 = about 4.8. What is the limiting reagent? I think that's H2 and it will produce about 8 mols H2O. How much O2 will be used. Tha...

Chemistry-Gases
Zn + 2HCl ==> H2 + ZnCl2 Use PV = nRT and solve for n = number of mols H2 at the conditions listed. Convert mols H2 to mols Zn, then g Zn = mols Zn x atomic mass Zn. b) Convert mols H2 to mols HCl, then M HCl = mols HCl/L HCl. Solve for L and convert to mL.

Chemistry
Grace, this is one of several you've posted. Most are more or less the same. Rather than piece meal all of this out,and get one answer at a time, tell me what your problem is with these questions and learn how to do them yourself.

Chemistry
Mg(OH)2(s) ==> Mg^2+(aq) + 2OH^-(aq) I don't know how your prof wants to show the water. Usually it is shown as H2O and placed OVER the arrow but sometimes as H2O as if it were a reactant. The only problem doing it that way is the equation then isn't balanced.

Chemistry
You may not be able to post for a few days but I think you can read responses. Here is how you do this problem. You want 7.30g Ni. 96,485 coulombs will deposit 58.7g/2 or 29.35g Ni. so you will need 96,485 coulombs x (7.35/29.35) = approx 24,000 coulombs but that's an esti...

Chemisty
0.027 volts = -(0.05916/2)log(x/0.1) Solve for x.

chemistry
Cu^2+ comes out before H^+ at the negative electrode. But I think the 1.23 occurs before 1.09.

Chemistry
H2O(aq) + H2O(aq) ==> H3O^+(aq) + OH^-(aq)

Chemistry
mols Ba(OH)2 = M x L = ? mols OH^- = twice that of Ba(OH)2

chemistry
Use (p1v1/t1) = (p2v2/t2)

chemistry
4Fe + 3O2 ==> 2Fe2O3 0.50 mol Fe x (2 mol Fe2O3/4 mol Fe) = 0.50 mol Fe x (2/4) = ? mol Fe2O3.

Chemistry
You only need the definitions. Here they are. 1. Oxidation is the loss of electrons. 2. Reduction is the gain of electrons 3. The material oxidized is the reducing agent. 4. The material reduced is the oxidizing agent. Zn is 0 on left and +2 on the right. H is +1 on the left a...

chemistry
Mg + what acid? HCL? Mg + 2HCl --> H2 + MgCl2 mols H2 = grams/molar mass Use the coefficients in the balanced equation to convert mols H2 to mols Mg. Now use mols Mg and convert to grams. g = mols Mg x atomic mass Mg.

Chemistry
Use the Arrhenius equation. k = Ae^-[Ea/(RT)]

chemistry
Do you have a question?

Chem
mmols NH3 = mL x M = 75.0 x 0.200 = 15.0 mmols HNO3 = 28.0 x 0.500 = 14.0 .......NH3 + HNO3 ==> NH4NO3 I......15.0....0........0 add...........14.0....... C.....-14.0..-14.0.....+14.0 E.......1.0.....0......+14.0 So you are 1.0 mmol away from the equivalence point. Basicall...

Chemistry
Separate the two half reactions. Na ==> Na^+ and H^+ ==> H2 Balance the atoms (so we're comparing apples with apples when we start the electron loss and gain). Na is ok. 2H^+ ==> H2 Do them one at at time. Na ==> Na^+ + e Next do the other one. 2H^+ + 2e ==>...

chem
That's the way you are supposed to do follow ups. I always check to see if there is a follow up. I think al of the volunteers do that although the time it takes us to get back varies according to how busy we are and how much time we have to spend answering questions. Hope ...

chem
I see you gave me all of one minute before typing your same problem.

chem
I posted the answer only a few minutes after you posted the restriction. How fast do you think I can type. Patience, please.

Chemistry
Hg(ClO3)2 + Na2S ==> HgS + 2NaClO3 mols Hg(ClO3)2 = grams/molar mass = ? mols Na2S = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Hg(ClO3)2 to mols HgS. Do the same to convert mols Na2S to mols HgS. It is likely these two values will no...

Chemistry
The HH equation is much easier but here is the other. (NH3) = 0.40M (NH4Cl) = (NH4^+) = (Cl^-) = mols/L = 0.1mol/0.500L = 0.2M ...........NH3 + HOH ==> NH4^+ + OH^- I........0.40..........0.20.......0 C..........-x.............x.......x E.........0.40-x.......9,.20+x....x K...

Chemistry
This is a buffer problem. Use the Henderson-Hasselbalch equation.

chemistry
Assuming the only ingredients could be decomposed to give oxygen (and nothing else) then oxygen driven off must have been 8.9-4.9 = ? Then mol = grams/molar mass.

chemistry
Yes, your reasoning is flawless and your calculations are superb EXCEPT that you have only two significant figures in 7.1; therefore, you may not have more than 2 s.f. in the answer. So 0.086903 would become 0.087 rounded to 2 s.f. If you omitted a zero on 7.1 than you would b...

Chemistry URGENT/DR BOB
What valve is the problem talking about? Where is it connected. What does it do. There must be more to the problem than what you've written.

chemistry
1. mols P = grams/molar mass 2. Convert mols P to mols P4O10 using the coefficients in the balanced equation. 3. Convert mols P4O10 to g. g = mols x molar mass.

Chemistry
HCl + KOH ==> KCl + H2L mols KOH = grams/molar mass mols KOH = mols HCl from the 1:1 ratio (coefficients) in the balanced equation. Then M HCl = mols HCl/L HCl. You know mols and M, solve for L and convert to mL.

Chemistry URGENT
Not only are you confused, surely you didn't post all of the question. You need to rephrase the question so that it is clear.

Chem 1
delta E = delta H + work 7785 = q + (-346) Solve for q. Then q = mass x specific heat x (Tfinal-Tinitial) You know q, mass, Tfinal and Tinitial. Solve for sp. h. .

Chemistry
mols K2Cr2O7 = grams/molar mass Then M = mols/L solution. You can use this information to calculate the concn of the Fe^2+ in the 10.00 mL sample of unknown ferrous solution BUT you won't now the concn of the original without knowing what the original volume was.

chemistry
Ba(OH)2 + 2HNO3 ==> Ba(NO3)2 + 2H2O mols HNO3 = M x L = ? mols Ba(OH)2 = 1/2 that from the coefficients in the balanced equation. Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2. YOu know mols and L, solve for M.

Chemistry
Two stoichiometry problems; one for Cu(OH)2 to CuSO4 and one for Cu(OH)2 to NaOH. Stoichiometry problems, for the most part, are worked the same way. Step 1. Convert what you have (100 g Cu(OH)2 to mols. mols = grams/molar mass = ? Step 2. Convert mols Cu(OH)2 to mols NaOH. Yo...

chemistry
mols CO2 grams/molar mass CO2 = about 7.7 = mols C. mols H2O = grams/molar mass H2O = 138/18 = about 7.7 so mols H atoms is twice that or about 15.4 Now find the ratio. The easy way is to divide everything by the smaller numbr C = 7.7/7.7 = 1.00 H = 15.4/7.7 = 2.00 So empirica...

Chemistry
C6H12O6 ==> 3C2H4O2

Chemistry
I disagree that the half reaction method is easier in all circumstances; in fact, I think it is harder to do them this way for these three than straight trial and error. Let me illustrate on the last one. Here is what I do. C2H6O + O2 ==> CO2 + H2O I look and see 2C on the ...

High school AP chem
mols Mn(OH)2 = grams/molar mass =? Then M Mn(OH)2 = mols/0.1L = ? . Let's call this y because I don't have a calculator with me. ........Mn(OH)2 ==> Mn^2+ + 2OH^- I.......solid.......0........0 C......solid........y........2y E.......solid.......y........2y Ksp = (M...

chemistry
Oxidation is the loss of electrons. Reduction is the gain of electrons. Zn is +2 on the left and +2 on the right. H is +1 on the left and +1 on the right. O is -2 on the left and -2 on the right. Cl is -1 on the left and -1 on the right. Anything change? nope. So nothing is ox...

chem Help
Substitute the equilibrium concentrations into the Kc expression and solve for Kc. Use this below. ...........N2 + O2 ==> 2NO I.......0.200..0.200....0.800 C.........+x...+x.......-2x E.....0.200+x..0.200+x...0.800-2x Substitute the E line into Kc expression along with the ...

Chem
mols Mn(OH)2 = grams/molar mass = approx 3E-6 but this is an estimate. You should recalculate this and all that follows. Then M = mols/L = about 3E-6/0.1L = about 3E-5. ...........Mn(OH)2 ==> Mn^2 + 2OH^- I..........solid........0.......0 C..........solid........x.......2x ...

Chemistry !
See your other post.

Chem Please Help
.........A <==> 2B I......2.30M.....0 C........-x......2x E......2.30-x....2x Kc = 5.04E-6 = (B)^2/A Substitute the E line into Kc expression I have above and solve for x. Then 2x = (B)

Chem 2 help
0.800 mol/2.00L = 0.400M ........2SO3 <==> 2SO2 + O2 I.....0.400M........0.....0 C.......-2x........2x.....x E.....0400-2x......2x.....x x = O2 = 0.140mol/2.00L = 0.07M Then 2x = 0.140M = (SO2) and 0.400-0.140 = 0.26M = (SO3) Substitute these into the Kc expression and s...

Chemistry - Solubility
I must confess I don't understand this at all.

chemistry
I guess A is one atom, B is another atom, what's n. Perhaps the number of B atoms? Or is that supposed to stand for the number of unpaired electrons?

chemistry
what's abn mean?

chemistry
qwater = mass H2O x specific heat H2O x (Tfinal-Tinitial) Note: Tfinal-Tinitial = delta T = 10.20 C.

Chemistry
I can't type this in the format you want because the site won't handle it. So n1 will be a and n2 will be b. 1/wavelength = R(1/a^2 - 1/b^2) n1 = a = 1. 1^2 = 1 n2 = b = 3. b^2 = 9 1/wavelength = R(1/1 - 1/9). R = 1.0973E7 wavelength will be in meters. Then E = hc/wave...

Chemistry
2NaN3 ==> 2Na + 3N2 mols N2 gas = grams/molar mass = x mols N2 Using the coefficients in the balanced equation, convert mols N2 to mols NaN3. That's x mols N2*(2 mols NaN3/3 mols N2) = x mols N2*(2/3) = ? mols NaN3. Then ? mols NaN3 x molar mass NaN3 = grams NaN3.

Chemistry
Same process + a little more from the NaN3 problem above. Find mols aspirin produced by 100 g salicylic acid, convert to grams aspirin, and that is the theoretical yield. Then % yield = (actual yield/theoretical yield)*100 = ?

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