# Posts by DrBob222

Total # Posts: 54,973

science
First, what experiment have you done? Second, are you looking for someone to write your paper for you. We're not inclined to do that.

word problem
C = # children A = # adults ---------------- A + C = 312 9.00A + 3.50C = 1884 Solve these two equations simultaneously for A and C. Post your work if you get stuck.

Chemistry
Check your work. I found 9.52. I used 9.26 for pKa. 14-4.74 = 9.26

Chemistry
See your other post. NH is the base. Remember to change Kb to pKa.

Chemistry
Close but I wouldn't round it off to 4.7.

Chemistry
Use the Henderson-Hasselbalch equation. the salt is the base.

Chemistry 212
Yes, that is right if yu use it correctly. To use it, just substitute 100 for Ao and 50 for A and solve for t which then will be t1/2 Actually it doesn't matter what number you pick for Ao as long as A is 1/2 that. Another way and slightly shorter is to tkae ln 1/2 (which ...

science
It would be nice to know what layers b and d are.

Physical Science
Total R. 1/R = 1/R1 + 1/R2 + 1/R3 Then I = E/R

Chemistry
mols CoBr2 = grams/molar mass = ? Then m - mols/kg solvent.

Chemistry
% = grams solute/100 g solution

Science
https://www.nrdc.org/stories/global-warming-101

Spelling
unspry as in can't get around very well

chemistry
Every four hours means 6 in a 24 hr period so 6 x 10 = 60 mg.

Chemistry
I don't understand the question the way it's worded.

Chemistry
Call CH3COONa = NaAc and HAc is acetic acid; i.e., CHCOOH. It's the Ac^- that is hydrolyzed. .......Ac^- + HOH ==> HAc + OH^- I....0.08..............0.....0 C......-x..............x.....x E....0.08-x............x.....x Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(0.08-x). ...

Chemistry
24 C doesn't sound very cold to me.

CHEMISTY
If we knew the molarity you wanted for the buffer we could calculate it. I suppose not knowing the M you must make it up and measure. So I would take 10 mL of the acetate stock and 10 mL of the acid stock, mix, and add drop wise and with stirring, NaOH until the pH meter reads...

Chemistry
I didn't check out our equation but I don't get that answer. INstread I plugged your answer in to see if it would plate out 1.27 grams, as follows: Coulombs = 0.002528 x 20 x 60 = approx 3 coulombs. 96,485 coulombs will plat out 63.55/2 = 31.775 g Cu so 31.775 x about ...

science
The answer isn't 1. The posts are spaced 2.5 m apart so between the 5th and 15th post there are 9 spaces of 2.5 m each. 9*2.5 - 22.5 m. distance = rate x time. 22.5 = rate x 2.5 seconds. Solve for rate (velocity).

Science
I didn't look up the link Ms. Sue gave but I lived there for almost 60 years. The one nearest me was the Atchafalya Basin. Try pronouncing that name. https://en.wikipedia.org/wiki/Atchafalaya_Basin

SCIENCE CHEMISTRY
And what other information do you have available. You must have some way to calculate atomic masses of O and H. Or is it OK to look those up on the periodic chart.

SCIENCE CHEMISTRY
Please use the same screen name. We halp better if you do that.

Science
And you don't have a clue? Look up the answers for a definition of each

science
Now if we knew what atoms were in area a, b, c, and d we might be able to help you.

bonding types of compounds
I am not impressed with any of the choices but a seems to be the best. By the way, you will get more help and faster help if you tell what you don't understand about your question. Just posting a question and expecting us to answer each and every one is not the way we like...

Science
I agree with resistor.

chemical reactions
a is not true. b is not true. c is confusing to me. d is your best best I think.

Chemistry
.....PtS ==> Pt^2+ + S^2- I....solid....0......0 C....solid....x......x E....solid....x......s Ksp = (Pt^2+)(S^2-) You know Ksp, substitutethe E line into the Ksp expression and solve for x = solubility in mols/L. Convert mols/L to grams/L with grams = mols x molar mass...

chemistry
Unless you have experimental evidence for the value, most of the time we assume it is 1. Often that is far misleading.

Chemistry
E = q + w 117J = -40.1J + (-20.3 J) This doesn't add to 117; I don't understand the problem. Perhaps another tutor can help.

Intermediate Maths
mass = volume x density mass = 2,500 mL x 0.64 g/mL = ?

Chemistry
yes

ap chemistry
Is go nitrogen a different kind of nitrogen? N2 + 2O2 ==> 2NO2

Chemistry
The correct answer is D. https://www.google.com/search?q=percent+fat+in+daily+diet&ie=utf-8&oe=utf-8 To explain further about the cereal box in my pantry, 60 g fat at 9 calories/grams is 540 calories. 540 calories on a 2000 calorie/day diet is (540/2000)*100 = about 27%. D is ...

Chemistry
I agree with your answer to 1 but not two. My cereal box says total fat should not exceed 60 g for 2000 calorie/day diet. That makes your answer look skimpy to me. Note; A gram of fat is about 9 calories; you can work out the percent from that..

Opinion Ques
I agree with Ms. Sue

chemistry
To bad you didn't show how you got that number. I could have looked at it and found the problem. mols CuBr2 = gams/molar mass = ? Then M = mols/0.5L = ?

Chemistry
The HCl was standardized with what? You have NaCO3 and that can't be. Is it NaHCO3 or Na2CO3. If Na2CO3 I must know what was used for the indicator.

chem
You don't need the temperature but you do need Keq unless, as I suspect, the author of the problem wants us to assume that the decomposition is COMPLETE. If that's the case, it is done this way. .......N2H4 ==> N2 + 2H2 I......800......0.....0 C.....-800......800......

Chemistry
k = -.693/t1/2</sub Solve for k, then ln(No/N) = kt. No = 2.40 N = solve for this You know k from above. t = 120 months.

Chemistry
pH = 11.12. Convert to pOH. pH + pOH = pKw = 14 so pOH must be 14-11.12 = 2.88 Convert to OH^- pH = -log(OH^-) (OH^-) = about 0.0012 but that's just a close estimate. You should redo that estimate for a better answer. .......NH3 + HOH ==> NH4^+ + OH^- I......0.1...

Chemistry
In calories. heat lost by 16.2 g steam @ 100 C to condense to liquid is q1 = mass x heat condensation. q1 = 16.2 x 540 cal/g = ? q2 = heat lost with H2O liquid moving from 100 C to 0C. q2 = mass H2O x specific heat x (Tfinal-Tinitial) = 16.2 g x 1 cal/g*C x 100 C = ? Total ...

chemistry
ln(No/N) = kt (c) part. Let No = 100 to start. then N = 50 at end. ln(100/50) = 2.2E-5*t 0.693 = 2.2E-5*t and t = about 30,000 hours but that's just a close estimate. You should get a better answer. Post your work if you have problems.

Chemistry
Your equation isn't balanced and is incorrect. Its diprotic because it has two H atoms that ionize. molecular equations are H2SO3 ==> H^+ + HSO3^- and HSO3^- ==> H^+ + SO3^2- but I think the question is asking just for the first one to show it gives H3O^+. The net ...

Chemistry

Chemistry
Ecell = (-0.0592/2)log Q You know Ecell is 0.024 v Q from the equation you wrote is (?Zn^2+)/(Zn^2+ 0.1) or it may be better to write Q as Q = (x/0.1) and solve for x = ?M Zn^2+ on the right hand side of the equation. Post your work if you get stuck.

math URGENT HELPPPP!
http://mathworld.wolfram.com/TriangularPyramid.html

Chemistry
Just convert grams Mg to mols Mg and you have it. g Mg/min = 1.5/3.0 = 0.5 g Mg/min or 0.5 g/24.3 = approx 0.02 mol Mg/min. or convert at the beginning but it's more work. 6.00/24.3 = approx 0.25 mols Mg initially. 4.50/24.3 = approx 0.19 mols final. (delta mols Mg) = ...

Chemistry
Your 0.5 mol HCl needed and 18.25 g needed are correct but it's the long way of going about it. However, you have no connection between this work and the 37 g/100 that you have in the stock. You can complete your work by mass = volume x density or 18.25 = volume x 1.19 or ...

Chemistry
......AgCl ==> Ag^+ + Cl^- I.....solid.....0......0 C.....solid.....x......x E.....xolid.....x......x NaCl is complely ionized (100%) so ....NaCl ==> Na^+ + Cl^- I...0.1M.....0.......0 C...-0.1....0.1......0.1 E....0......0.1......0.1 Ksp = (Ag^+))Cl^-) Ksp you know. (Ag...

chemistry
It's hard to do on this forum because I can't draw a picture. But I'll try. To be polar we muct have a molecule that is NOT symmetrical in space AND it has polar bonds. Here are some examples. You know you have a polar bond if the electronegativity (EN) between the...

Chemistry
I responded to this same questipin earlier. Look before you leap.

thermodynamic
q = mass x specific heat x (Tfinal-Tinitial)

Chemistry
CaCO3 + H2SO4 ==> CaSO4 + H2O + CO2. CaSO4 is a white ppt and the CO2 will snuff out the match flame. Mg + 2HCl ==> H2 + MgCl2. H2 fizzes and will burn (explode--a minimal one at the mouth of the test tube). Mg reacts with HNO3 to give various compounds depending upon ...

Chemistry
Use the Henderson-Hasselbalch equation. NH3 is the base; NH4Cl is the acid.

@steve--science
Is it ok to mix m and km?

Chemistry
Add up the atomic masses. Fe + S + 4*O + 14*H + 7*O = ?

chemistry check
I'm not sure what's going on. Yes, pH of 0.01M HCl is 2 and you're doing that right on the calculator to get that answer. As for the other. if you want the pOH of a solution, which seems to be another separate problem, you use pH + pOH = pKw pKw is 14 so pOH = 14-...

chemistry
Interesting, I suppose, but I don't see a question. Do you have some proof that Fe2O2 exists. Or would be written better as FeO?. Perhaps you meant Fe2O3.

chemistry
Cu is +2 S is S O is -2. 4*-2 = -8 All compounds add to zero. Cu + S + 4*-2 = 0 2 + S +(-8) = 0 2 + S + -8 = 0 Solve for S. S = 0 - 2 + 8 = ?

Chemisty
Decreasing temperature decreases molecular motion, the molecules strike the sides of the balloon less frequently and with less energy, therefore the pressure is decreased which results in a volume decrease. The reverse takes place when the temperature is increased.

Chemistry
rate = delta (I2)/delta T. rate = (0.4-0.2)/30 min.

Organic Chemistry
Is this NMR? High resolution? I don't know if this will help but here it is. http://www.chemguide.co.uk/analysis/nmr/highres.html

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

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

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.

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