Tuesday
July 29, 2014

Posts by DrBob222


Total # Posts: 43,217

MAth
4+sqrt(4+x^2)=x sqrt(4+x^2) = x-4 square both sides 4+x^2 = x^2-8x+16 You can finish.

CHEMISTRY
I'm not sure I agree completely with what you posted but do you have a question here?

Chemistry
I don't have the solubility tables nor do I have them memorized. I suspect you have either a graph or a table that gives you some of that information. If you will post that perhaps we can help.

chemistry
pH = 3.45 3.45 = -log(H^+) (H^+) = approx 3.55E-4. ...........HA ==> H^+ + A^- I.........0.1.....0.....0 C..........-x.....x.....x E.........0.1-x...x.....x where x = 3.55E-4 Substitute that into Ka expression and solve for Ka.

chemistry
The equation is wrong. 24.0 what? 0.982 what? KClO2 is not right. Straighten this out, watch for typos, perhaps we can help.

chemistry
Use PV = nRT and substitute the SECOND set of numbers to fine the NEW number of mols.

Chemistry
Did you get a definitive answer to the SO2/O2/SO3 question?

Chemistry
HCl + NaOH ==> NaCl + H2O millimols NaOH = 15 x 0.1 = 1.5 mmols HCl = 25 x 0.1 = 2.5 Excess HCl = 2.5-1.5 = 1 (HCl) = (H^+) = 1 mmol/40 mL = ? Convert to pH.

check answer
I believe that's right; or 500*sin(35)

Chemistry
I don't get it. It appears to me that any number one chooses can go there. Without O2 along with SO2 there is no way to establish equilibrium for SO2 alone or for O2 alone.

Chemistry
2C4H10 + 13O2 ==> 8CO2 + 10H2O 24.643 initial mass -24.592 after using -------- 00.051g mass butane used. mols butane = grams/molar mass = estimated 0.00088 but you need to get a more accurate figures. Using the coefficients in the balanced equation, convert mols butane to ...

chemistry 2
dSrxn = (n*dSproducts) - (n*dSreactants)

Chemistry
mols Mg = g/atomic mass = 5.2/24.3 = about 0.21 but you need a more accurate figure. mols HCl = L x M = 0.4 x 1M = about 0.4 Convert mols Mg to mols H2 = about 2 x (1 mol H2/1 mol Mg) = about 0.21 mol H2 Convert mols HCl to mols H2. That's 0.4 x (1 mol H2/2 mols HCl) = abo...

Chemistry
First, there is no way for me to know if these titrations have reached the equivalence point since the concn is unknown; however, I suspect what you really want to know is the concn of the unknown material Ba(OH)2 + 2HCl ==> 2H2O + BaCl2 mols Ba(OH)2 = M x L = 0.0217 x 0.05...

Chemistry
Do we start from scratch or do we have KNO3 to begin with? To start from scratch, take 25 mL 1M HNO3 and add to 25 mL 1M KOH. Evaporate to near dryness, place in a drying oven and leave until dry. Pure dry KNO3 is the result.

Chemistry
You don't say but I assume A and B are gases. total mols = mols A + mols B X(A) = mol fraction A = mols A/total mols. XB = mols fraction B = mols B/total mols pA = XA*Ptotal pB = XB*Ptotal

Chemistry
I agree.

Chemistry
I did, too.

Chemistry
That's right.

Chemistry
nope. E is true.

Math Personal Finance
doubled in ?? years.

Math Personal Finance
2000 x 0.10/4 = interest at end of quarter 1. Then 2000 + interest = total and I'll call that a. Then a x 0.10/4 = interest earned in quarter 2. interest + a = total at end of quarter 2 and I'll call that b. Continue for 3rd and 4th quarters.

Math Personal Finance
It will earn 0.55 x 4000 = ? annually. ? x 2.5 years = total interest earned. 4000 + interest earned = balance at maturity.

engineeering
You don't have a question here. And you can make your post much simpler if you don't write the underscore marks. We know C656H1707O756N11S where the subscripts are.

oops--Chemistry
I made a typo in that cubic equation. 4x^3-6.68E-7x^2+1.67E-8x-1.04E-10 = 0

Chemistry
It's close but not right. 1.67E-7 = (2x)^2(x)/(0.025-2x)^2 is what you started with and that's correct. Your error was in expanding the denominator. 1.67E-7 = 4x^3/(6.25E-4 -0.1x +4x^2) The next step is to multiply 1.67E-7 x the denominator, then collect the terms in d...

chemistry
See your post above which Bob Pursley answered.

chemistry
I can tell you how to do it if you can tell me how you get a concn of anything less than zero. I can see (OH^-) = 1 x 10^-80 but that is still more than zero. Not by much I'll grant you, but still more than zero.

chemisrty
5 is the answer. 5.5 to 3.5 the solution has become more acid by pH of 2 and since this is a log term (pH = -log(H^+) that's more acidic by a factor of 100. So OH must have decreased by a factor of 100.

chemistry
I think you meant this for the equation. I followed with the next two lines showing acid, base, conj acid, conj base. I think if you type the equatiion right you will see the answer. Also you need to restructure the answers to get them right. CO(NH2)2 + HOH ==> CONH2NH3^+ +...

chemisrty
Yes. Very good.

chemistry
mols KOH = grams/molar mass Then (KOH) = mols KOH/L solution Then (OH^-) = (KOH) since KOH is a strong electrolyte and dissociates completely. I would then do pOH = -log(OH^-) and follow with pH + pOH = pKw = 14 and solve for pH.

Chemistry/physics
What's the trouble here? Change 12.65 eV to joules = KE and solve for v. m = approx 9.11E-31 kg but you should confirm that since my memory isn't all that good any more.

science
I think 0.400 m/dm3 meant 0.400 mols/dm3 = 0.400 M.

chemistry
I don't see a question here.

chemistry
How many mols do you want? That's M x L = 0.400 x 0.500 = ? Then mols = g/molar mass. You know molar mass and mols, solve for mols.

chemistry
I'll show you how to do a and I expect you can do the rest but I can help you through them if necessary. Call benzoic acid HBz. ..........HBz ==> H^+ + Bz^- I.........1.0M....0......0 C..........-x.....x......x E........1.0-x....x......x Then 6.3E-5 = (x)(x)/(1.0-x) You...

Chemistry
250 x 0.82 = estimated 205 g starting FeS2. Convert 205 g to mols = about 2 mol but you should confirm that. Then mols H2SO4 = 2 mols FeS2 x (8 mols SO2/2 mol FeS2) x 0.95 x (2 mol SO3/2 SO2) x 0.90 x (1 mol H2SO4/1 mol SO3) x 0.90= mols H2SO4. Convert to grams.

Chemistry
M H2S2 initially = 0.0125/0.5 = 0.025M ............2H2S ==> 2H2 + S2 I...........0.025.....0.....0 C............-2x......2x.....x E.........0.025-2x....2x.....x Substitute the E line into the Kc expression and solve for x.

physical science
You mean it isn't obvious that I think the answer is concentrated?

physical science
I think the word that goes there is "concentrated" solution; however, dilute could be right under the right circumstances as well as saturated and unsaturated. I think the question could have been stated better.

Chemistry
Benzoate ion hydrolyzes in water to form a solution that is not neutral. If we call the benzoate ion Bz^-, then .........Bz^- + HOH ==> HBz + OH^- I........1.0..............0.....0 C........-x..............x.....x E.......1-x..............x......x Kb for Bz^- = (Kw/Ka for H...

chemistry
mols HAsc = 5/molar mass = approx 0.03 but you need to do it more accurately. ........HAsc ==> H^+ + Asc^- I......0.03......0......0 C.......-x.......x.......x E......0.03-x....x......x Substitute the E line into Ka expression for HAsc and solve for x, then convert to pH.

Chemistry
An organic acid is R-COOH where R stands for any organic group. A is an ester B is an alcohol etc.

chemistry
http://en.wikipedia.org/wiki/Cis%E2%80%93trans_isomerism

Chemistry
See your post above.

chemistry
6.3E1 mL or 6.3 x 10^1 mL To write any number in sci notation. place the decimal after the first digit, then count the places from the decimal to the end of the number and write "x 10^n" or "x 10^-n" where n stands for the number of places you counted. It i...

Science
Just for clarity; yes for A and yes for B.

Science
yes.

Science
pH + pOH = pKw = 14. You know pH and pKw, solve for pOH. Then pOH = -log(OH^-)

chemisty
Remember the definitions. Oxidation is the loss of electrons. So Cu goes from +1 to zero and iron goes from zero to +2. Which loses electrons?

Chemistry
The titration is a 1:1 titration of KHP and KOH. KOH + KHP ==> H2O + K2P mols KHP = grams/molar mass mols KOH = mols KHP (look at the coefficients in the balanced equation; they are 1:1) M KOH = mols KOH/L KOH

Chemistry
There is nothing wrong with Damon's response but I do these slightly differently. Chemistry thinks in mols. So we ask ourselves "How many mols do I need?" That's mols = M x L = 0.1 x 0.500 = 0.05 Then mols = grams/molar mass 0.05 = g/36.5 and solve for g = 36...

Chemistry
I worked this for you below.

chemistry
3 is a synthesis.

chemistry
2NI3 ==> N2 + 3I2 I looked up the enthalpy for this and found it to be -290 kJ/mol. Therefore, 10 g would be -290 kJ x (10/2*molar mass NI3) = ?

Science - chemistry
Use the Henderson-Hasselbalch equation. millimols HCOOH = mL x M = 100 x 0.05 = 5 ......HCOOH + NaOH ==> HCOONa + H2O I.......5.......0........0........0 add.............x................ C.......-x.....-x........+x E.......5-x......0........x x = base 5-x = acid Substitute...

Science - chemistry
See your other post. mmols HCOOH = mL x M = estimated 5.4 mmols NaOH = mL x M = estd 5.4 ......HCOOH + NaOH ==> HCOONa + H2O I.......5.4.....0........0.......0 add............5.4............... C.......-5.4..-5.4.....5.4........ E.......0.......0.......5.4 So this is not a ...

Help Chemistry
All you will ever need to know about redox and balancing. http://www.chemteam.info/Redox/Redox.html

Science
The free energy is such that the reaction is spontaneous for iron to be oxidized to iron(II) with HCl but not to iron(III). In fact, if any iron(III) were formed the thermodynamics are such that it would be reduced to iron(II) immediately with the excess iron therre initially....

Chemistry
Is that a typo for KOH? KOH + HA ==> KA + H2O mols KOH = M x L = ? Then mols KOH = mols HA since the coefficients are 1:1. mols HA = grams/molar mass. You know mols and grams, solve for molar mass.

Chemistry
I'll do the Ca(OH)2 but the process is the same for LiOH. Ca(OH)2 + 2HCl ==> 2H2O + CaCl2 step 1. Write and balance the equation. step 2. Convert what you have, in this case Ca(OH)2), to mols. mols = M x L = 0.600 x 0.050 = 0.03 mols Ca(OH)2. step 3. Using the coefficie...

chemistry - please help
As far as I know there is no general formula for solubility of solutes in solvents. I think you must find the solubility in tables or by experimentation.

Chemistry
Refer to your question above for Ca(OH)2 and HCl.

Chemistry
See your other post.

Chemistry
a and d; formula unit

science 1 question!!!
http://www.ask.com/question/how-are-valley-glaciers-and-continental-glaciers-different

chemistry---كيمياء
mols K from KCl = M x L = ?. volume = 0.1L mols K from K2SO4 = M x L x 2 = ? volume = 0.2L M K after mixing is total mols K/total volume in L.

Chemistry
Look up the delta H formation for the materials in your text/notes. Then dH rxn = (n*dHo formation products) - (n*dHo formation reactants)

Chemistry
...........HA --> H^+ + A^- I.........0.01....0......0 C..........-x.....x......x E........0.01-x...x......x Ka = 1E-6 = (H^+)(A^-)/(HA) Substitute the E line into Ka expression and solve for x = (H^+).

chemistry
............2IBr ==> I2 + Br2 I........ 0.0124......0....0 C...........-2x.......x....x E........0.0124-2x....x....x Keq = 4.13E-5 = (I2)(Br)2/(IBr)^2 Substitute the E line into Keq expression and solve for x = (Br)2 = (I2)

Chemistry
The procedure is right and it appears you have substituted correctly but I didn't go through the math. It's a little easier if you use (P1V1/T1) = (P2V2/T2) and you get the answer in one math operation instead of two.

Chemistry
I have trouble following what you've done. The first part where you end up with 1081.67 mL is not right for two reasons. 1. The formula should be V1/T1 = V2/T2 2. You didn't convert T to kelvin. The second calculation you did is correct.

chemistry
Please don't post in all caps. It makes the question difficult to read. 0.1 mol NO2 and 0.2 mol N2O4. So you have 0.1 mol N from NO2 = 0.05 mol N2 from NO2. You have 2*0.2 = 0.4 mol N2 from N2O4. Total is 0.4 + 0.05 = ?

chemistry
See the S8 and NO2/N2O4 problems.

chemistry
I don't know what a wave point is. 1 mol C atoms is 12 grams and that contains 6.02E23 atoms C.

chemistry
1 mol NaOH = 40 grams and that contains 6.02E23 molecules NaOH.

chemistry
You need to find the caps key on your computer and use it. mols S in 9.8 kg H2SO4 = grams/molar mass = 9800/molar mass H2SO4 = estimated 100 8S ==> S8 100 mol S x (1 mol S8/8 mol S)

chemistry
See your other post above.

Chemistry
To do what? Is that a combustion reaction or something different. If combustion it will be (CH3)2CHCH2OH + 6O2 ==> 5H2O + 4CO2 Use the coefficients in the balanced equation to convert mols isopropyl alcohol to mols O2. That will be 3.5 mol isop x (6 mols O2/1 mol isop) = 3....

chemistry
XO2 = 0.68 pO2 = XO2 x Ptotal

Chemistry
Your set up is right. This is a common ion problem and the effect of the CoBr2 (Br is the common ion) DECREASES the solubility of CuBr as you would predict from LeChatelier's Principle. CoBr2 is a soluble salt and dissociates at 100% to CoBr2 --> Co^2+ + 2Br^- ............

Science
Did you look at these? https://www.google.com/search?q=alpha-1+antitrypsin+deficiency%3F&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb

chem
mass = volume x density

Chemistry
right

Chemistry
Note the correct spelling of celsius. mols C10H8 = grams/molar mass = 7.58/molar mass C10H8 = ? Then molality = m = mols/kg solvent m = mols from above/0.120 = ? Then delta T = Kb*m. You know Kb and m, solve for delta T, then add that to the normal boiling point of benzene in ...

chemistry
You can't follow the instructions?

chemistry
Please don't write in all caps. It makes the question difficult to read. mols NaCl = grams/molar mass Change mL to L. Then M = mols/L solution.

science
First, I'm not a biologist and I suggest you confirm these. From what I can find on the web I think 1,2,3,5,and 6 are correct. I'm wondering if an alternate choice in 4 is leaves and an alternate choice in 7 is chloroplasts. If so I would consider reversing the answers...

not complete---science
no chart

chemistry
For H^+, e is in n = 8 so the follwing transitions can occur. n = 8 to n = 7 8 to 6 8 to 5 8 to 4 8 to 3 8 to 2 and 8 to 1; then n = 7 to n = 6 7 to 5 7 to 4 7 to 3 7 to 2 and 7 to 1; then n = 6 to n = 5 6 to 4 6 to 3 6 to 2 and 6 to 1 You get the idea here. Do the same for th...

Chemistry
2KOH + H2SO4 --> K2SO4 + 2H2O mols KOH = M x L = estimated 0.01964 and it will react with 1/2*(0.01964) = estd 0.00982 mols H2SO4. How much H2SO4 do you have? That's M x L = estd 0.0139 so you have more than enough H2SO4 to exactly neutralize it. That means an excess of...

chemistry
mols CaCl2 = grams/molar mass M = mols CaCl2/L soln

Chemistry
I think you're right about A. Wouldn't you need to work to make KE into PE? C. To evaporate H2O you must add heat so that must be endo. D. If you burn a piece of wood that is combustion. It gets hot, right? So that must be? E. When water freezes it is exothermic. No, I...

Chemistry
And you think what? and why?

Chemistry
Under some circumstances the last one COULD be right but I agree with your answer. I obtained 32.5 L of the gas at STP and most reactions will occur if there is an excess of reagent and the conditions are right.

Chemistry
I think the problem is this. I believe you have calculated N for N2O5 correctly. That's N2O5 LEFT. Then 1-N = mols N2O5 that decomposed to form O2, take 1/2 that and convert to V using PV = nRT If I do that I obtain 6.76 which rounds to 6.8L. I don't remember but I may...

Chemistry
I agree with all of the answers given by Bob Pursley. The correct choice from your list is #8. You haven't entered the correct choice; i.e., 8.

Chemistry
(HCHO) = (H2) = (CO) = 1 mol/2L = 0.5 M add (HCHO) = 2/2 = 1.0M add (CO) = 1/2 = 0.5M ..........HCHO(g) --> H2(g) + CO(g) E........0.5M........0.5M.....0.5M add.......1.0M..........0......0.5M Substitute the E line into Kc expression and calculate Kc. #2. a. Since the syste...

chemistry
Take enough solution to have 1 mol total. That means you have 0.15mol H2SO4 and 0.85 mol H2O. Convert H2O to grams which is 0.85 x (18 g H2O/mol H2O) = approx 15 Then m = mol/kg solvent m = 0.15/0.015 = ? estimated.

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