# Posts by DrBob222

Total # Posts: 54,805

Chemistry
.....4A + 3O2 ==> 2A2O3 ..0.5386...x.....0.711 x = 0.711 - 0.5386 = 0.1724 g O2. Convert g O2 to g A2O3. Let A = atomic mass A and O = atomic mass O. 1724 x (2*molar mass A2O3/3 molar mass O) = 0.711. Then 0.1724 x (4A+6O)/6O) = 0.711 Substitute and solve for A. My answer ...

chemistry
HNO2 + KOH ==> KNO2 + H2O mols HNO2 = M x L = ? mols KOH = mols HNO2 from the balanced equation. Then M KOH = mols KOH/L KOH. You know M and mol KOH, solve for L and convert to mL.

Chemistry
right

Chemistry
That's right.

Chemistry
We can't draw structures on this forum but these two links should help you decide. https://terpconnect.umd.edu/~wbreslyn/chemistry/Lewis-Structures/lewis-structure-for-PH3.html https://terpconnect.umd.edu/~wbreslyn/chemistry/Lewis-Structures/lewis-structure-for-SF4.html

chemistry HELP
a. I will call acetate Ac^-. ......Ac^- + HOH ==> HAc ==> OH^- I...0.128.............0......0 C......-x.............x......x E...0.128-x...........x......x Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(0.128-x) Solve for x = (OH^-) and convert to pH. I let mmol sand for ...

Chemistry
You are not given Ksp, That's what you are to calculate. You have g/100 Cr(OH)3. Multiply by 10 gives you g/L. Divide by molar mass to get mols/L. Then plug that into Ksp expression fopr (Cr^3+). That times 3 gives you the (OH^-). Then solve for Ksp. Post your work if you ...

Science
You don't say if the solute is volatile or non-volatile. I assume it is volatile. Since X is used for mole fraction, I will change the unknown compound to Y. mols Y = 2/32 = ? mols CS2 = 100/76 = ? total molsl = ? + ? = ? Then XCS2 = mols CS2/total mols = ? XY</sub) = ...

73. Because this is chemistry you're intimidated. % anything = (mass of that/total mass)*100 %Fe in Fe2O3 = (2*atomic mass Fe/molar mass Fe2O3)*100 = ? Works the same way for Fe3O4. 78. Sorry, I don't understand this one. Neither XYY nor XY makes sense to me. Read that...

Chemistry
Higher temperature causes more molecular motion, more molecules move from the liquid to the vapor state.

chem
PV=nRT Solve for n = number of mols. Don't forget T must be in kelvin.

chem
Right !. Good work. By the way, that equation I wrote is not balanced. It should be 2Cr + 3Cl2 ==>2CrCl3 Obviously you corrected that before you worked the problem.

chem
Find the caps key on your keyboard and use it. This is a limiting reagent (LR) problem. Here is a procedure that will work all of your LR problems. 1. Write and balance the equatin. Cr + 3Cl2 ==> 2CrCl3 2a. Convert grams Cr to mols. mols = grams/atomic mass = ? 2b. Do the ...

Chemistry
I answered this question for you last night. You need to look for our responses before re-posting.

Chemistry
Here is what you need to know. Use this information to make your sentences. The Henderson-Hasselbalch equation is pH = pKa + log (base)/(acid) Knowing what pH you want and the pKa of the acid, calculate (base) and (acid) you need to prepare the pH you want. base is propanoate...

chemistry
I'm not inclined to give you all of these answers. Something is amiss here. Just what do you not understand about all of these. There is WIDE range of chemistry here.

Chemistry
rate = k(N2O5)^1 You know k and (N2O5) solve for rate. Note: I believe you meant (N2O5) = mols/L^-1.

Chemistry
Looks like it to me. (-CH2-CH2-)n

Chemistry
I don't think what you propose will work. HF is a weak acid but most of the H^+ comes from the HCl. Some smaller amount comes from the HF. I would do it this way. (HCl) = 0.05 x (100/400) = ? HCl ==> H^+ + Cl^- so H^+ from this source is approx 0.012M. (HF) initial ix 0...

chemisty
You really need to find the caps key on your keyboard and use it. First, calculate the solubility, S, in the saturated solution of Ca(OH)2. That is ......Ca(OH)2==>Ca^2+ + 2OH^- I.....solid......0.......0 C.....solid......S.......2S E.....solid......S.......2S Plug the E ...

CHF02
Your question needs some serious help. Nothing about the experiment. What about steps 1-5? If you will start at the beginning and write a lucid question someone here will be glad to help.

Chemistry
Diprotic is H2A. It ionizes in two steps. H2A ==> H^+ + HA^- and HA^- ==> H^+ + A^2- The triprotic is H3A and it ionizes in 3 steps.

chemistry
Here is a good site to read about water pollution. Much of the article covers soluble material but there is some on insolubles, also. https://en.wikipedia.org/wiki/Water_pollution#Organic.2C_inorganic_and_macroscopic_contaminants

Chemistry
mols AgNO3 = grams/molar mass = approx 0.3 but you need a better answer than that estimate. Convert mols AgNO3 to mols CaCl2. That means approx 0.3 x (1 mol CaCl2/2 mols AgNO3) = approx 0.15 mol CaCl2. Then M CaCl2 = mols CaCl2/L CaCl2. You have M CaCl2 and mols CaCl2, solve ...

Chemistry
In a NON-buffered solution, it is ....ZnCO3 ==> Zn^2+ + CO3^2- I....solid....0........0 C....solid....S........S E....solid....S........S C....solid....S........S where S is the solubility of ZnCO3. But in a buffered solution, not all of the anion is in the form of CO3^2-. ...

Chemistry
See your post above.

science-MS.SUE PLZ HELP
copper. Element. Pure substance. salt. I assume you mean table salt but there are many salts. It is pure if it is 100% salt, NaCl. It is a compound. Water is a compound. It is a pure substance. Carbon monoxide is a compound and a pure substance. Mud is a mixture. Some parts of...

science
This sounds like you want us to do your research paper. The tutors here are not inclined to do that. But we will be happy to critique what you prepare.

science
I suggest you read about the kinetic molecular theory in your text. In addition, Google that phrase. There is a lot of information on the net.

science
I could but you will remember the information better if you do them yourself. You can find the answers to 3 and 4 if you will Google Archimedes Principle. The answers are quite clear. For 6, all you need to do is to look up the definitions of the answer choices and the correct...

science
I disagree with 3,4,6.

Balancing chemical equations
Cl2 + SO2 + 2H2O ==> H2SO4 + 2HCl

PCB
I wonder if PCB is a subject.5% what? w/w, w/v? I'll assume 5% w/w. That will make it 5 g urea + 95 g H2O. mols urea = grams/molar mass = ? mols H2O = grams/molar mass = ? Total mols = the sume XH2O = mols H2O/total mols. psoln = XH2O*PoH2O Post your work if you get stuck.

Chemistry
Br is -1 on the left; +5 on the right. Loss of 6e. Al is +3 on the left; 0 on the right. Gain of 3e. Multiply the Br half by 1. Multiply the Al half by 2. Then balance the H^+ and H2O Post your work if you get stuck.

Chemistry
0. You haven't asked a question; I assume the problem is to determine the %Sb in the sample. 1. Balance the equation. 2. mols KBrO3 = M x L = ? 3. Using the coefficients in the balanced equation, convert mols KBrO3 to mols Sb^3+ 4. g Sb = mols Sb x atomic mass Sb. 5. %Sb...

Chemistry
Yes, there is only one way the reaction can go but the problem asks for Ecell but doesn't say it is spontaneous. If it doesn't go spontaneously the Ecell is not the same.

Chemistry
You don't show a reaction. Show what you've done and I'll find the error.

Chemistry
Look up the electronegativity of each atom and subtract them. The most polar bond will be the one with the largest difference. Example: for d. C is approximately 2.5 and O is approx 3.5. Diff is 1.0 For C. C approx 2.5 and N approx 3.0 for diff of 0.5 so CO bond is more polar ...

Chemistry
mols = M x L = ?

chemistry
.......BaSO4 ==> Ba^2+ + SO4^2- I......solid......0.......0 C......solid......x.......x E......solid......x.......x But with [HO^+] added, that combines with the SO4^2- to give HSO4^- as this: ......SO4^2- + H^+ ==> HSO4^- and increases the solubility of BaSO4. In other ...

Chemistry
I believe the stability decreases from sulfate to selenate to telurate. I believe that is a matter of size of the central metal ion.

physical chemistry
mols phenolphthalein = grams/molar mass = ? molality = m = mols/kg solvent Then delta T = Kb*m. You have m and Kb, solve for delta T. Then boiling point = 100 + delta T.

Chemistry
L1 x M1 = L2 x M2 15L x 0.3M = L2 x 15M L2 = ?

chemistry
P1V1 = P2V2 Substitute and solve for V2.

chemistry
Use PV = nRT and solve for n = number of mols. Then mols = ? Don't forget to change T to kelvin and use P in atm. Then mols = grams/molar mass. You know mols and grams, solve for molar mass.

Chemistry
The rate is increased and the equilibrium is shifted to the right.

Chemistry
Use PV = nRT and solve for n = mols. Convert mols O2 to mols KClO3 using the coefficients in the balanced equation. then grams KClO3 = mols KClO3 x molar mass KClO3.

Chemistry
There may be a shorter way to do this but off the top of my head here is what I think you need to do. Post your work if you get stuck. .......N2O4 ==> 2NO2 I......0.1........0 C...-0.058*0.1..+0.058*0.1 E......?...........? Solve for Keq which I will call k1. That gives you...

chem
pH + pOH = pKw = 14 = 14 You know pH, and pKw, solve for pOH. Then pOH = -log(OH^-) Solve for OH^- )in mol/L Then M = mols/L. You know M and L, solve for mols Finally, mols = grams/molar mass. You know molar mass and mols, solve for grams.

Science - heat
I agree with both answers.

Chemistry
So what's the problem? You have no data.

Chemistry
Use (P1V1/T1)=(P2V2/T2) Standard conditions are P2 = 760 torr, T = 273 K. Don't forget to change 30 C to K. K = 273 + C

Physcial Science
If the question is to determine the heat absorbed by the metal she must know the specific heat of the iron.

Physical Science
q = mass x specific heat x delta T. For Al: q = 1 g x 0.90 x 5.6 = ? Follow the same process for Fe.

Chemistry
It's Al and not Al2 2Al + 3I2 ==> 2AlI3

Chemistry
This is a limiting reagent (LR) problem. Zn + 2HCl ==> H2 + ZnCl2 mols Zn = grams/atomic mass = ? mols HCl = M x L = ? Using the coefficients in the balanced equation, convert mols Zn to mols H2. Do the same to convert mols HCl to mols H2. More than likely the two values ...

Chemistry
M = mols/L mols = g KCl/molar mass KCl You know mols and you know L, solve for M.

Chemistry
No way of knowing or calculating the Keq. You may mean the expression. That is Keq = (C^2/(A^3)(B^2

Chemistry
2C8H18 + 25O2 ==> 16CO2 + 18H2O mols C8H18 = grams/molar mass = approx 0.5 but that's just an estimate as are all the numbers that follow. mols CO2 produced = approx 0.5 x 16/2 = approx 4. approx g CO2 = mols cO2 x molar mass CO2 = ? This is the theoretical yield (TY)in...

chemistry
q = mcdT q = ? volume = 3.81m x 20.0m x 12.5m = ? m^3 and convert to mL. Since the density is 1.00 g/mL, that will be the mass. dT = Tfinal-Tinitial

Chemistry
In most cases it is the metal but in some cases it is the metal oxide

Chemistry
For 53 mg/mL and you want 100 mL so 53 x 100 = 5300 mg of the salicylate, place in a 100 mL volumetric flask, add water and make to the mark on the volumetric flask. 0.02M FeCl3. That means 0.02 mols/L or 0.002 mols/100 mL. How much is 1 mole? mols = g/molar mass. You know ...

chemistry
According to the site below there is 3-5% lactose in butter milk. https://en.wikipedia.org/wiki/Lactose_content_of_foods As an average if we take 4%, and if we assume that is % w/v, there will be 4 g lactose in 100 mL or 40 g/1000 mL. # mols in 40g is mols = grams/molar mass ...

chemistry
NaOH + HCl ==> NaCl + H2O mols HCl = M x L = ? mols NaOH = mols HCl (from the 1:1 coefficients in the balanced equation) grams NaOH = mols NaoH x molar mass NaOH % NaOH = (g NaOH/g sample)*100 = >

chem
F2 replaces other halogen ions below it. Cl2 replaces halogen ions below it. Br2 replaces halogen ions below it. I2 replaces halogen ions below it. So you know A isn't right. Which one is?

chemistry
Your question says 0.01m which is 0.01 MOLAL. Since you apparently don't know how to use the caps key I suspect you mean 0.01 M (MOLAR) but I'll go with 0.01 m since you ask about 250 g solution. 0.01m means 0.01 mols/kg solvent. How many mols do you have in 250 g? ...

chemistry
Who says Bi2S3 and CuS will not dissolve? In most circumstances they will

biology---Chemistry
More like biology.

Chemistry
mols you need = M x L = ? mols = g/molar mass. You know mols and molar mass, solve for grams. 2. mL1 x M1 = mL2 x M2 mL1 x 12 = etc.

Chemistry
MnO4^- + 8H^+ + 5e ==> 4H2O + Mn^2+

Chemistry
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch7/

Chemistry
How many electrons does Be have?

Chemistry
I answered this below.

Chemistry
What don't you understand about this? The answer is B. A, C, D are true.

Chemistry
Constant T. Use P1V1 = P2V2

Chemistry
What size flask? I will assume 100 mL volumetric flask AND I will assume adding solid NH4Cl does not change the volume. M NH3 = 14.5 x 55 mL/100 mL = ? mols NH4Cl = grams/molar mass = ? M NH4Cl = mols/L pH = pKa + log(base)/(acid) You are given pKb. PKa + pKb = pKw = 14 Post ...

Chemistry
2 is wrong. 1 and 3 are right. 9 is confusing; the answer depends upon how the question is interpreted. If it means the fewest H3O^+ IN SOLUTION the answer is C. If it actually means the fewest H3O^+ PRODUCED then both C and D are right. Neither C nor D PRODUCES a H3O^+.

Chemistry
Al goes into solution; Zn comes out. 2Al + 3ZnSO4 ==> Al2(SO4)3 + 3Zn(s) Atoms balance. Charges balance. 6 electrons lost (2Al ==>2Al^3+ + 6 e) and 6 electrons gained (3Zn^2+ + 6e ==> 2Zn).

Chemistry
Bob Pursley answered this just a day or so ago but I can't find it or I would give you a link. Here is how to do it. First you need to determine the limiting reagent. H2 will require 100 kPa O2 to react completely; you have that much so H2 must be the limiting reagent. ...

chemistry
dG = -RTlnKsp Use 8.314 for R

Chemistry
pH = pKa + log base/acid pH = 4.26 pKa = 4.82 So log A/HA must be negative. Which (A or B) will make it negative?

math
90 - 90(x) = 49.1

math
What's 13.5% of 3 hrs? Convert that to seconds. There are 50 seconds in an hour and 60 seconds in a minute. Post your work if you get stuck.

math
let x = amount in savings 8000-x = amount invested -------------- 0.05x + 0.08(8000-x) = 600 Solve for x and 8000-x

math
960-840 - 120 interest in 3 years. That's \$40/yr So if you had 840 at the end of the first year you must have started with _______?

math
mL1 x %1 = mL2 x %2 60 x 0.12 = mL2 x 8 mL2 is TOTAL. You already had 60. So you must add ______?

math
How much fruit juice is in each? Jackson: 3 gallons x 0.20 = ? Bonanza: 2 gallons x 0.55 = ? Total = ? % juice = (total juice/total gallons)*100 = ?

Chemistry
Look up Sn(s) ==> Sn^2+ + 2e and Pb^2+ + 2e ==> Pb(s) add them to find Ecell. Then dGo = -nFEcell. Post your work if you get stuck.

chemistry
.......Ca(OH)2 ==> Ca^2+ + 2OH^- I......solid........0.......0 C......solid........x.......2x E......solid........x.......2x Ksp = (Ca^2)(OH^-)^2 Substitute the E line into the Ksp expression and solve for (Ca^2+). 2x that will be (OH^-) if you want to know that. The ...

chemistry
Your question is a bit vague but if you're doing an experimental determination for sugar and you have a standard solution, the amount you put into the standard is the "true" concn while the value obtained by your experimental set up is the experimental concn. ...

chem
2Al + 3H2SO4?Al2(SO4)3 + 3H2 mols Al = grams/atomic mass Al. Using the coefficients in the balanced equation, convert mols Al to mols H2SO4. That will be mols Al x 3/2 = mols H2SO4. Now convert mols H2SO4 to grams. grams = mols x molar mass = ? 2. mols Al from above. Convert ...

che
I think this is a flawed problem. The density isn't given and without that one doesn't know the volume of the solution; therefore I don't think an accurate molarity can be calculated. A 37% solution of HCl has a molarity of very close to 12 M and the density is ...

Chemistry HELP!!!URGENT
http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/dope.html Go to Google and type in semiconductors & dopants

chemistry
Monoprotic acids have only one H and that goes with the OH of a base to form water. To form an acid salt you need another H ion. Example: Acetic acid, HAc, reacts with NaOH to form a salt + H2O. HAc + NaOH ==> NaAc (sodium acetate) + H2O but you've used the only H in ...

Chemistry
Your guess is wrong. If the solution is unsaturated you will LESS Ca^2+ and LESS SO4^2-. The saturated solution will have dissolved more of each ion.

chemistry
You will have Na2SO4 solid, Na^+(aq), SO4^2-(aq), H2O(l)n H2O(g)

CHEMISTRY
Vrms = sqrt(3RT/M) 3 = 3 R = 8.314 T = temperature M = molar mass All you needed to do is to go to google and type in rms speed molecules.

CHEMISTRY
rms = sqrt (3RT/M) where M is molar mass.

chemisrty
Aw C'mon. P is pressure in atm, R is the gas constant in L and atm, T is kelvin temperature. This is just a rearrangement of PV = nRT.

chemisrty
P*molar mass = density*RT density will be in g/L.

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