Thursday
December 8, 2016

Posts by DrBob222

Total # Posts: 53,750

chemistry
73.67 g is right but I would round that to 74. I don't know that there is a way to "DERVIVE" the formula. That's one of those things you learned in the 4th grade arithmetic class. But here is a common sense approach. If I gave you a basket containing 5 lbs of...
October 7, 2016

chemistry
That's 2 Al for 6e or 1 Al for 3e so that factor should be 2*26.98/6e or 26.98/3e. That doubles the answer. Some books use 96,485 instead of 96,500. Thanks for showing your work. That always makes it easier to find the error.
October 7, 2016

Chemistry
All of the answers for 1 are true but I don't think A is the best one. 2,3,4 are not right.
October 7, 2016

Chemistry
And what is the final temperature of the water?
October 6, 2016

Chemistry
An exothermic reaction has dH - so it must be B or E
October 6, 2016

Chemistry
I would look at D
October 6, 2016

AP Chemistry
I don't know how you're defining the term potential level. The potential to oxidize Cl ion to Cl2 gas is -1.36 v and that for Na ion to Na metal is -2.71 v. The potential of the cell is -1.36 + (-2.71) = -4.07 v. Therefore, you need at least +4.07 v to electrolyzs ...
October 6, 2016

Chemistry
http://wwwchem.uwimona.edu.jm/courses/selrules.html
October 6, 2016

Chemisrty
I have corrected the typo in the equation below. H3C6H5O7(aq) + 3NaHCO3(q)---Na3C6H5O7(aq) + 3H2O(l) + 3CO2(g) 1. mols NaHCO3 = grams/molar mass = 1/84 = 0.0119 Convert mols NaHCO3 to mols H3C6H5O7 using the coefficients in the balanced equation. That's 0.0119 x (1 mol ...
October 6, 2016

Chemistry
I don't know the meaning of 5A----10^20. "in a cobalt 'what' contain 5A---10^20 'what'"?
October 6, 2016

Chemistry
Materials, usually chemical molecules, in which one end of the molecule is positive and the other end is negative.
October 6, 2016

Chemistry
With regard to atomic weight or atomic mass see this. https://www.google.com/search?q=what+unit+is+atomic+mass&ie=utf-8&oe=utf-8 But one mole of the element will weigh that number shown in grams. with regard to the ionic radius of He and H, I don't have an answer. I didn&#...
October 6, 2016

Chemistry
You're ok. I substituted the numbers into equation 2 (with pKa = 5.3 and pH = 5.6
October 5, 2016

Chemistry
I tried that early on. The problem I had is that we have two equations and three unknowns. The unknowns are a, x, and pKa. I don't know how you solve for a in terms of x without involving pKa. So I'm inclined to think your solution is not correct but I don't know ...
October 5, 2016

Chemistry
I checked and you did respond to my question; however, you didn't answer it.
October 5, 2016

Chemistry
CH3COOH = HAc. .....HAc --> H^+ + Ac^- I....0.5.....0......0 C.....-x.....x......x E....0.5-x...x......x Ka = (H^+)(Ac^-)/(HAc) Substitute the E line into Ka expression and solve for H^+ initially in the 10 L. Then (OH^-) = Kw/(H^+) to calculate OH^- Double that. ...
October 5, 2016

Chemistry
All three of these reactions are double replacement. Therefore, all you need to do is to write the reaction and look up each compound to see what state it is. For example, NH4Cl(aq) + AgNO3(aq) → NH4NO3(aq) + AgCl(s) etc.
October 5, 2016

Chemistry
https://www.google.com/search?q=molar+volume+water&ie=utf-8&oe=utf-8
October 5, 2016

Chemistry
You need to look up the solubility of each of the compounds. That will give you the answer since one of them is essentially insoluble.
October 5, 2016

CHEMISTRY PLS HELP
delta T = i*Kf*molality. You know i = 3 from CaCl2. You know Kf (or you can look it up). I THINK it's about 1.9 or so. All you need is the molality. You have the M. Convert this way. Assume you have a liter of solution so the mass of solution is 1000 mL x 1.5 g/mL = 1500 ...
October 5, 2016

byu
See you post above.
October 5, 2016

Chemistry
M = mols/L solution You know M, you know mols, solve for L.
October 5, 2016

Chemistry
Correct. Go to the head of the class.
October 5, 2016

Chemistry
Technically I don't think you can work this problem without knowing the specific gravity of the solution. You can assume that the volume of the solution is the same as the mass (0.1 g = 0.1L as Sandu has done which means you assume the density of the solution is 1.00 g/mL...
October 5, 2016

Chemistry
The solution to this problem hasn't jumped out at me. Will you please check that all of the information from the problem has been posted?
October 5, 2016

chemistry
delta T = Kf*molality Substitute for delta T and Kf and solve for molality. m = mols/kg solvent substitute for m and kg solvent and solve for mols. mols = grams/molar mass Substitute for mol and molar mass and solve for grams glycerin.
October 5, 2016

chemistry
80 g = dish+xtals+H2O -40 g = dish+xtals ------ 40 g = dish+xtals -20 g = xtals ------ 20 g = dish
October 5, 2016

Chemistry
I think you have lucked onto the right answer but not the right reasoning. Two ways to look at it. First way. PV = nRT. V,R,T are constant(k) so pressure = k(n) So more mols the higher P; therefore, we go with water. Second way. Since the balloon is expandable, the end ...
October 4, 2016

Chemistry
You need to do these yourself. What do you not understand about this question? Aqueous solutions that end up with solids usually are pptn reactions. Loss/gain electrons in a reaction are redox reactions. Those that produce water, especially if they are from OH and H containing...
October 4, 2016

Chemistry
Frankly, I don't think you have copied the problem correctly. Where did the 16.042 in your work come from?
October 4, 2016

Chemistry
With some minor variations, all of these stoichiometry problems are alike. Step 1. Write and balance the equation. You have that. Step 2. Convert what you have to mols. That is mols = grams/molar mass = 350g/117 = approx 3 but you need to confirm all of these estimates here ...
October 4, 2016

oops--Chemistry
To clarify, I gave you ppm MgCl2 so ppm Cl^- is twice ppm for the MgCl2 "molecule". Like Scott, I too would consider throwing out the 175 value but as I re-read the question I don't think that is an option.
October 4, 2016

Chemistry
mean M = sum of M/5 = ? Then mean M x molar mass = grams/L. Change that to mg/L and that is ppm.
October 4, 2016

chemistry
Here is my work so far: 212 X 0.831 = 176.172 X 34.2 q = mass metal x specific heat metal x (Tfinal-Tinitial) q = 212 x 0.831 x (125.0-34.2) = ? q gained by water = mass H2O x specific heat H2O x (Tfinal-Tinitial) = ? By the way, I don't like the way you wrote your ...
October 4, 2016

Chemistry
You have 100 mL x 0.1M = 10 millimols HA and 10 mmols KA. ....HA + KOH = KA + H2O I...10....0....10........ add.......x............. C..-x....-x....+x E...10-x..0....10+x Substitute the E line into the Henderson-Hasselalch equation and solve for x = millimols KOH that must be ...
October 4, 2016

Chemistry
Here is the answer I posted yesterday. This information will help you find the answer yourself. If you don't understand something give me the details and I will help you through that part of it. http://www.jiskha.com/display.cgi?id=1475448164
October 3, 2016

Chemistry
Frankly I think this problem is lacking some information. As an estimate this is what I would do. pH at the half way point is 5.0 which means the pKa of HX is 5.0 and that makes Ka = 1E-5. At the eq point you have the hydrolysis of X^- (the anion) as .....X^- + HOH ==> HX...
October 3, 2016

Chemistry
match so the compound is zero charge as in NH4NO3 NH4HCO3 (NH4)2SO4 (NH4)2HOI4 etc.
October 3, 2016

Chemistry
You can read more about standard additions here. https://en.wikipedia.org/wiki/Standard_addition y = mx + b is straight line. m is slope = 0.103 b is the intercept = 0.135 and that will be - if the x intercept. Then solve for x = concentration in ppm. It is unclear in the ...
October 3, 2016

Chemistry
CxHyOz ==> xCO2 + 1/2yH2O Convert g CO2 and g H2O to g C and g H. 0.561 g CO2 x (atomic mass C/molar mass CO2) = grams C. 0.316 g H2O x (2*atomic mass H/molar mass H2O) = grams H. 0.255 - g C - g H = grams O. mols C = grams C/atomic mass C = ? mols H = grams H/atomic mass H...
October 3, 2016

General Chemistry
20 breaths x (500 mL/breath) = ? mL. Now convert mL to m^3. 1 cubic meter = 1E6 mL
October 2, 2016

Chemestry
There are 6.02E23 molecules in 1 mol of MgCl2. Each mols MgCl2 contains 3 ions.
October 2, 2016

Chemistry
2Na + S ==> Na2S mols Na = grams/atomic mass = ? Using the coefficients in the balanced equation, convert mols Na to mols Na2S. That's ?mols Na x (1 mol Na2S/2 mols S)= ?mols Na x 1/2 = ? Then grams Na2S = mols Na2S x molar mass Na2S
October 2, 2016

Chemistry
mols NH3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols NH3 to mols NO. That's ?mols NH3 x (4 mols NO/4 mols NH3) = ?mols NH3 x 1/1 = ? Then grams NO = mols NO x molar mass NO
October 2, 2016

Chemistry
1.In the following chemical reaction, how many grams of the excess reactant are left over when 0.45 moles of Al react with 1.25 moles of Cl2 ? 2Al + 3Cl2 → 2AlCl3 LR = limiting reagent. ER - excess reagent. Actually you work three regular stoichiometry problems here. ...
October 2, 2016

Chemistry
See your post above.
October 2, 2016

AP Chemistry
21.3 g Fe2O3 x (2*atomic mass Fe/molar mass Fe2O3)= ? You don't need the mass of the sample of 12.8 grams. That would be needed only if you wanted % Fe in the sample.
October 2, 2016

Chemistry
Oxidation is the loss of electrons. Reduction is the gain of e.electrons. For 1. Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Zn on left has oxidation state (OS) of 0. Zn on right has(OS) of +2. So that's a loss of 2e which makes Zn to Zn^2+ oxidation. Cu^2+ on the left has ...
October 2, 2016

CHE 111-03L
Half the volume means pressure is increased. An increase in P makes the reaction shift to the side with fewer mols. Fewer mols is on the right. So it shift to the right. By the way, DON'T count the 4X. X is a solid and doesn't enter into this. 2. Removing some X has no...
October 2, 2016

Chemistry
The problem tells you. 30.65 cm^3 = 30.65 cc = 30.65 mL. 1 cc = 1 mL = 1 cubic centimeter = 1 cm^3.
October 2, 2016

Chemistry
If you want this done with equivalents, then mL x M x (molar mass KIO3/6000) = grams KIO3
October 2, 2016

Chemistry
0.01 M in KI is correct. It isn't bad wording; all of the KNO3 stuff is put in there to confuse you.
October 2, 2016

Chem
Yes, x comes from the solution of your ICE table. I didn't check you math but that's what you do.
October 2, 2016

Chem
You're right on target. Solve the equation you've set up. Then % decomp = (2x/8.913)*100 = ?
October 2, 2016

Chemistry
I think you have interpreted correctly IF (that's a big IF) the graph is reading absorbance versus concentration of I^-.
October 2, 2016

Chemistry
What specific evidence from the gold foil experiement led Rutherford to come to each of the following conclusions? I would not have answered as you did. You may mean the same thing I'm writing but I think it's better said. The nucleus occupies very little space in the...
October 2, 2016

chemistry
% w/w = (mass solute/total mass solution)*100 = ? mass solute = 1.60 grams. mass solution = 20.0 + 1.60 = 21.60 grams. Substitute and solve.
October 2, 2016

chemistry
reactants ==> products (dHformation products) - (dHformation reactants) = dH reaction.
October 2, 2016

chemistry
For 4p. n = 4 l = 1 m can be -1, 0, or +1
October 2, 2016

CHEMISTRY
2C2H6 + 7O2 ==> 4CO2 + 6H2O mols C2H6 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C2H6 to mols CO2. That is ?mols C2H6 x (7 mols O2/2 mols C2H6) = ? = ? Now convert mols CO2 to grams. g CO2 = mols CO2 x molar mass CO2 = ?
October 2, 2016

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O mols HCl = grams/molar mass = ? mols Ba(OH)2 = 1/2 that (from the coefficients) Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2 = ?
October 2, 2016

Chemistry
-3.42 kcal/g x (76g/mol) = approx -260 kcal/mol CS2 + 3O2 ==> CO2 + 2SO2 + 260 kcal/mol
October 1, 2016

Chemistry
The problem doesn't tell you the mass of the sample (nor the volume) and density). As is the problem can't be solved.
October 1, 2016

Chemistry
Sn = 0.00383 mols I = 0.01534. The easy way to find the ratio is to divide the smaller number by itself (thereby assuring you will get 1.000), the divide the other number by the same small number. Sn = 0.00383/0.00383 = 1.00 I = 0.01534/0.00383 = 4.005 Then round to whole ...
October 1, 2016

chem
Instead of me working the problem for you and you checking my work, why not show your work and let us check your work. Be happy to do that for you.
October 1, 2016

chemistry
What you have is a saturated solution since there is solid undissolved. A supersaturated solution will be completely dissolved and will in fact, have more dissolved than it normally can hold. If a single crystal of the solid is put into the solution,or if the sides of the ...
October 1, 2016

chemistry
It is still iodine; therefore, physical change.
September 30, 2016

more dump--Physics
Wouldn't it be better if you showed your work and let us check it for accuracy. That way we're checking you instead of you checking us.
September 30, 2016

Chemistry
Sorry to be so long but I had to leave home. The set up for 3c looks ok but I don't get that answer. Check your arithmetic. I get 9+ for an answer.
September 30, 2016

Chemistry
3a isn't correct. I didn't chck the others. It should be 10.7 x(1 mol O2/32g O2) x (2 mols CO2/1 mol O2) x (44 g CO2/mol CO2) = about 29 or so g CO2. Check your factors. The units don't cancel as they should.
September 30, 2016

Chemistry
pA is unchanged. Ptotal is increased. XB is decreased since total mols is increased.
September 30, 2016

Chemistry
yes
September 29, 2016

Chemistry
Why not draw the Lewis dot structure and see which one is not complete? Try drawing the Lewis structure for BF3 and see what you get.
September 29, 2016

Science
I have a very good question too. With no drawing, how in the world do we even know what you are talking about with distances D and H? We need to be mind readers? Some teachers may be able to do that but I'm not one of them.
September 29, 2016

Science
R = R R1 = R/5*5 = R/25 So (R/R1) = (R/R/25) = R*25/R = 25
September 29, 2016

Science
I think both answers are right. Metallic bonds often are higher melting point but they aren't compounds.
September 29, 2016

Chemistry
(n*BE reactants)-(n*BE products) = BE rxn.
September 29, 2016

Organic Chem
Read under "GC Analysis" https://en.wikipedia.org/wiki/Gas_chromatography
September 29, 2016

Chemistry
HCl + KOH ==> KCl + H2O mols KO = M x L = ? Using the coefficients in the balanced equation, convert mols KOH to mols HCl. (That's a 1:1 ratio you see). Then M HCl = mols HCl/L HCl.
September 29, 2016

Biochemistry
I don't think so. I'll look at your work if you post it.
September 29, 2016

Chemistry
Tough to do on this forum. 92U238. The 92 is a subscript on the left of U and the 238 is a superscript on the left of U.
September 29, 2016

Chemistry
How much heat to you need? That's q = mass H2O x specific heat H2O x delta T. q = 1000 x 4.184 x 10 = 41840 J a. (4J/min*cm^2) x (100 cm/1 m) x (100 cm/1m) x # min = 41840. Solve for # min b. C + O2 ==> CO2 + 393,000 J (393,000/12 g C) x #g C = 393,000 Solve for #g C
September 29, 2016

Chemistry
yes and yes. 8HNO3 + 3Cu ==> mols HNO3 initially = M x L = ? mols Cu = grams/atomic mass = ? Now calculate how much HNO3 is need to dissolve that many mols Cu. mols HNO3 remaining unreacted = initial mols HNO3 = mols needed to dissolve the Du = ?
September 29, 2016

Organic Chemistry
I tried drawing that out. I see the heptane and 4-secbutyl but not the 3,6 dimethyl. I looks like 3,5 dimethyl to me.
September 29, 2016

chemistry
Look up H2O going to oxygen
September 28, 2016

Chemistry
C60 + 60 O2 ==> 60CO2 dE = q + w Combustions are done at constant and W = -pdV. 60 mols CO2 come from 60 mols O2 so there no change in volume and no work. Thus dE = q = dH. dH formation would be the reverse; i.e., 60C --> C60 and dHrxn = dHformation C60. We don't ...
September 28, 2016

Chemistry
Do you want concn in M or g/L. I will assume you want molarity = M mols KCN = grams/molar mass KCN = ? Then ?mols/0.052 L = ? mols/L = M KCN. The NaOH just adds 2 mL to the total volume.
September 28, 2016

CHM 1020
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
September 28, 2016

chemistry
Assume you have 100 g sample; then, mols C = 74.27/12 = ? mols H = 7.79/1 = ? mols N = 12.99/14 = ? %O = 100-74.27-7.77-12.99 = 4.95% mols O = 4.95/16 = ? Now find the ratio of these elements to one another, round to whole numbers for the subscripts.
September 28, 2016

chemistry
Note: When the question asks for percent composition of a compound, it means to find the percent of EACH element in the compound.
September 28, 2016

chemistry
1.30M x (71/238) x [119/(119+105)] =?M
September 28, 2016

Chemistry
2. It is a double displacement reaction. Some may call it an acid/base reaction, also, but I think you want the first one. 3. H2CO3 ==> H2O + CO2 is decomposition reaction.
September 28, 2016

Chemistry
I believe you're on the wrong track. This is a hydrolysis equation; i.e., at the equivalence point of an acid/base titration, you are left with the salt and water. The salt hydrolyzes (unless it is the salt of a strong base/strong acid such as NaCl, KCl, KBr etc). ......CN...
September 28, 2016

Chemistry
Kayla M, this is done the same way as the HBr/KOH problem I solved for you earlier in the day. If you don;t understand something let me know what it is, in detail, and I can help you through it but after you've seen the process I'm not inclined to do your homework for ...
September 27, 2016

Chemistry
HC2H3O2 + NaOH ==> NaC2H3O2 + H2O mols acetic acid = M x L = ? Using the coefficients in the balanced equation, convert mols aceit acid to mols NaOH. You can see the ratio is 1:1. Then M NaOH= mols NaOH/L NaOH.You know M and mols, solve for L and convert to mL. 2. KHP + ...
September 27, 2016

Chemistry
See your other post.
September 27, 2016

Chemistry
Left to right in the periodic table the electronegativity (EN) increases. F is the most EN.
September 27, 2016

Chemistry
A is right. B is right. C. I would calculate n for each of the gases. You know partial pressure of each, V, R, & T from the first container. Mols Ne can be calculated from P Ne, V of the second container, R & T. Find total mols, use that with R, & T and total volume to find ...
September 27, 2016

AP Chemistry
I answered this 44 minutes after you posted it the first time. http://www.jiskha.com/display.cgi?id=1475010098
September 27, 2016

Chemistry
NH4^+ + H2O ==> H3O^+ + NH3
September 27, 2016

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