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Posts by DrBob222

Total # Posts: 54,502

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

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 ...

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 ...

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

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...

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

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 ...

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...

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

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

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

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

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. ...

Chemistry
See your post above.

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.

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 ...

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...

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.

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

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.

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

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

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

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...

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.

chemistry
reactants ==> products (dHformation products) - (dHformation reactants) = dH reaction.

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

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 = ?

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 = ?

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

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.

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 ...

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.

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 ...

chemistry
It is still iodine; therefore, physical change.

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.

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.

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.

Chemistry
pA is unchanged. Ptotal is increased. XB is decreased since total mols is increased.

Chemistry
yes

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.

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.

Science
R = R R1 = R/5*5 = R/25 So (R/R1) = (R/R/25) = R*25/R = 25

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

Chemistry
(n*BE reactants)-(n*BE products) = BE rxn.

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

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.

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

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.

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

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 = ?

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.

chemistry
Look up H2O going to oxygen

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 ...

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.

CHM 1020
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

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.

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

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

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.

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...

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 ...

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 + ...

Chemistry
See your other post.

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

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 ...

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

Chemistry
NH4^+ + H2O ==> H3O^+ + NH3

Chemistry
But that isn't ferrous ammonium sulfate. The correct formula is Fe(NH4)2(SO4)2. IN YOUR COMPOUND, (NH4)^+ is 0.360 so (SO4)^2- = 0.360 x (3 mols SO4/2 mols NH4) = 0.360 x 3/2 = ?

Chemistry
Look at your post below under Taylor. This is the same kind of problem. By the way we prefer that you use the same screen name on Jiskha. We can help you better that way.

too many typos---AP Chemistry
I made several typos. Here is the corrected. -3226.7 = [7*-393.5)+(3*-285.8)] - [dHbenzoic acid)-0] I get 385.2 kJ but a NEGATIVE sign. Check that.

AP Chemistry
dHrxn = (n*dH products) - (n*dH reactants) -3226.7 kJ = [(3*-393.5)+(3*-385.8)] - [(1*dHbenzoic acid) - (0)] and solvle for dHbenzoic acid.

Chemistry
HBr + KOH ==> KBr + H2O mols KOH = M x L = 1.569 x 0.51 approx 0.8. mols HBr = 0.8 (look at the coefficients in the balanced equation; 1 mol HBr to 1 mol KOH.) M HBr = mols HBr/L HBr = approx 0.8/0.635 = approx 12.6M mols HBr initially = 0.8 mols KOH added with 141 mL = M x...

AP Chemistry
A multistep problem. q1 = heat needed to raise T ice from -50 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to change solid ice at zero C to liquid water at zero C. q2 = mass ice x heat fusion ice. q3 = heat needed to raise T of liquid H2O ...

chemistry
NaCl BeF2 KI What's the problem here? What do you not understand about this? The periodic table almost TELLS you what to write.

Chem
Stoichiometry 101. 2CH4 + 2NH3 + 3O2 --> 2HCN + 6H2O What mass of NH3 is required for the synthesis of 1.5 × 105 kg of HCN if the reaction has a 97.5% yield? mols HCN = 150,000g/molar mass HCN = ? Using the coefficients in the balanced equation, convert mols HCN to ...

Chem
See your other post.

chemistry
5.75 g CuSO4.5H2O ==> CuSO4 + 5H2O 5.75 g x 0.36 = ? g H2O in 5.75 g CuSO4.5H2O

Chemistry
Maria--I tried to find your initial post and my response but failed. Here is what I remember about it. This is the most head scratching question I've seen in my career. The I^- is oxidized to IO3^- so you can write that half reaction easily. It is I^- + 3H2O ==> IO3...

Chemisty
2H2 + O2 ==> 2H2O mols H2 = grams/molar mass H2 = ? mols H2 x 1 = mols H2O grams H2O = mols H2O x molar mass H2O

chemistry
Lyman Series is from n = ? to n = 1; therefore, for 4th line, that is n = 5 to n = 1. E = 2.180E-18(1/1^2 - 1/5^2) = ?

chemistry
right

Chemistry
I wouldn't worry about the volume. p*molar mass = density*RT You know P, molar mass, density,and R.Solve for T (in kelvin).

Chemistry
Why not post the complete problem?

Chemistry
OK. I'm going with the flow. ...Ag(OH)2 + 2HBr ==> AgBr + 2H2O mols Ag(OH)3 = grams/molar mass = ? initial mols HBr = M x L = ? mols HBr used = 2*mols Ag(OH)2 mols HBr remaining = initial mols - mols used = ? Then M HBr left = mols/L and pH = -log (HBr) = ?

Ap Chemistry
Convert pKa to Ka. pKa - -log Ka Let's call saccharin just HS. M HS = grams/molar mass which I've estimated to be about 0.03 but you need a closer answer than that. .....HS ==> H^+ + S^- I..0.03.....0.....0 C....-x.....x.....x E..0.03-x...x.....x Substitute the E ...

Chemistry
It would have been so much easier if you had shown your work; then I could have found your error. First, you didn't balanced the equation. 2Na2O2 + 2CO2 ==> O2 + 2Na2CO3 mols Na2O2 = grams/molar mass = ? I have approx 0.3 but that's just an estimate. Use PV = nRT ...

Chemistry
For the metal.

Chemistry
What are your results in? grams nitrate? if so, then g N = g nitrate x (atomic mass N/molar mass NO3^-)

Chemistry
IO3^- + 3H2O ==> IO3^- + 6e + 6H^+ O3 + 2H^+ +2e ==> O2 + H2O --------------------------- You can get the molecular equation by multiplying equn 1 by 1 and eqn 2 by 3, then cancel ions common to both sides and you end up with this. 3O3 + I^- ==> 3O2 + IO3^-

biology
There is a C2H4 and a C2H6 but there is no neutral C2H5 atom. If it is C2H5^- then it is polar.

Chemistry
CuSO4(aq) + K2CO3(aq) ==> CuCO3(s) + K2SO4(aq)

CHEMISTRY HELP
I don't understand the question with your use of symbols. M stands for molarity but I think you mean molar mass NH3 is 17. I have no idea what M(NH3)= 8.5 g means nor H n(NH3) formed = 5 mol.

Chemistry (Help!)
See your post above.

chemistry
phex = Xhex*Pohex ppen = Xpen*Popen eqn1 Then Xpen = 1-Xhex eqn2 phex + ppen = 252 Substitute and solve these two equations for Xhex and Xpen. I worked through them and got about 0.4 for pentane and about 0.6 for hexane. Post your work if you get stuck.

chemistry
Sounds like a math problem to me. The way I read it, there is an excess moisture content of 10% so the $40/ton is reduced by $4/ton to make it $36/ton. It cost $1.00/100 lb or $20.00/ton for shipping [$1.00 x (2000 lbs/100 lb)] and 10% of the $20.00 is $2.00/ton so 40-4-2 = $...

Chemistry
The atomic mass of an element is the weighted average of the mass of all of the isotopes. 63(0.5) + 65(0.3) + 67(0.2) = ?

chemistry
CaC2O4 = 0.253 g 0.253 x (molar mass K2C2O4.H2O/molar mass CaC2O4) = ? g K2C2O4.H2O

chemistry
q needed to heat the water is q = mass H2O x specific heat H2O x (Tfinal-Tinitial). Note that if you use specific heat listed you must change 110 kg H2O to grams. 1 lb x (? J needed/2.2E7 J/lb) = lbs oil needed. Convert to kg oil.

Chem
1 g carbohydrate = 4 kcal 5.9 g x (3500/100) = ?g glucose. 4 kcal/g x ?g glucose = ?

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