Saturday
July 26, 2014

Posts by DrBob222


Total # Posts: 43,174

chemistry
I think I would try converting concn and time to change in rate and plot change in rate vs concn.

Chemistry Please Help!!!
http://chem-net.blogspot.com/2011/11/lewis-electron-dot-structures-simple_16.html

Chemistry Please Help!!!
This looks like it's down your alley. https://answers.yahoo.com/question/index?qid=20100302133652AAnVmL6 We can't draw structures on this forum. If I can find a lewis dot sturcture the nitride ion I will post as another link.

chemistry
mols HCl = M x L = ? mols NaOH = mols HCl M NaOH = mols NaOH/L NaOH. You know mols and M, solve for L and convert to mL.

chemistry
Surely you have a graph, a chart, a table, that gives you the solubility of these compounds at this temperature.

Chemistry
right.

Chemistry
mols KOH = M x L = ? mols H3PO4 = 1/3 mols KOH (look at the coefficients in the equation). M H3PO4 = mols H3PO4/L H3PO4.

chemistry
Use the Arrhenius equation.

Chemistry
Yes, you need M S2O3^- but surely you have more places than that in the answer.And I wouldn't think 14 mL is close enough. I would think something like four places(that is 14.22 mL). Also I think you have a typo; I believe the first equation after Ksp is not right.That sho...

Chemistry
How much of this can you do on your own? Where are you stuck?

Chemistry
In an enthalpy experiment total heat = (mass H2O x specific heat H2O x delta T) + Ccal x (delta T) I may misunderstand the question but I don't think you subtract the heat capacity of the calorimeter.

chem
q = mass Cu x heat vaporization

chemistry
m = mols/kg solvent 0.375 = mols/0.570 = ? Solve for mols. Then mol = grams/molar mass You have mol and molar mass, solve for grams.

CHEMISTRY (PLEASE HELP)
If your blank is larger than the sample by that amount I suspect contamination o the blank.

chemistry
2Zn + O2 ==> 2ZnO mols Zn = grams/molar mass = ? Convert mols Zn to mols ZnO Then g ZnO = mols ZnO x molar mass ZnO. This is the theoretical yield (TY). The actual yield (AY) is 242. %yield = (AY/TY)*100 = ?

chemistry
Use the Henderson-Hasselbalch equation.

chemistry
How do you define a 3:4 solution of KCl?

chemistry
1%........4%.........6% |...3.....|.....2....| An easy way to see this which I learned from Mathmate. So you take 2 parts of the 1% and 3 parts of the 6% to make 4%. So for 100 g you take 40g of the 1% and 60g of the 6% to make 100 g of 4%.

Chemistry
The usual things like misreading thermometers, invalid calculations, poor lab technique and all of the other errors likely to be made by a student. Mg may have not been pure, student may not have removed the oxide layer from the Mg ribbon, heat flow into or out of the calorime...

Chemistry
Na is right. The others are not. Na2SO3 is a salt and when it dissolves the SO3^2- hydrolyzes. Na2SO3 ==> 2Na^+ + SO3^2- 1.17M.....2*1.17...1.17 .......SO3^2- + HOH --> HSO3^- + OH^- I......1.17..............0........0 C.......-x...............x........x E.....1.17-x.......

chemistry
And the question is?

Chemistry
A complete calculation can be obtained at https://www.google.com/search?q=calculate+M+ions+in+H3PO4&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb and click on the Chapter 7 pdf file document. They use 5.0M H3PO4 and not 0.2 but the process i...

chemistry 185
You have two equations. pH = pK2for H3PO4 + log (base)/(acid) 7.4 = pK2 + log b/a solve for b/a and that's one equation. The second one is acid + base = molarity of solution. Since you want 9g/L and that x 12L you want that many grams in the 12L. Convert that to M. Then so...

chemistry
This doesn't look too complicated. Where is your trouble? I would choose A and D.

Chemistry
Then I have no idea what the question means. The delta Hformation Mg is zero. For anything else with Mg there must be some kind of reaction.

Chemistry
I assume you mean Mg to MgO. How will you burn Mg under water?

Chemistry
It means weigh out 12g glacial acaetic acetic acid. The density of glacial acetic acid is about 1.05g/mL and the stuff is about 99.5% pure so if you pipet 11.4 mL that will weigh 12g. However, I don't think you will find a pipet with the volume 11.4 mL. If the 12 g doesn&#...

Honors Chemistry
q = mc*delta T q = heat = 72,400J m = 752g c = specific heat = ? dT = 9.95 Solve for c.

chem
ascorbic acid is C6H8O6. mols ascorbic acid in 100 g is mol = grams/molar mass = 100/176.12 = ? There are 6 C atoms/mol acid, 8 H atoms/mol acid, and 6 O atoms/mol acid. mols C is 6x that. mols H is 8x that. mols O is 6x that.

chem
See your other post above.

science
I can't find anything on the web that gives a rate of solution for caster sugar. But all sites agree that caster sugar dissolves quickly.

chemistry
Sure. If the experimental value is less than the actual value the percent error is negative. If the experimental value is larger than the actual value the percent error is positive. But most (at least many) people use the absolute value of the error when reporting in which cas...

Chemistry
Sorry but I don't understand the question.

Chemistry
The pure element is zero. All elements in their standard state are zero.

statistics

Chemistry
NOPE. T is not 2.3, that's delta T for the experiment. The initial T is 23.1 so that must be the T of the methane when it's added to the bomb or 294.25K and that gives n = 0.0112 or about 11.2 millimoles.

Chemistry
I don't know the context of the problem but your 979 kJ/mol appears to be right if you have the number of significant figures correct. Does the problem say anything about "about 10.0 millimoles" methane? You have P, V, R, and T and you can calculate n. If I can c...

chemistry clearly step by step
I agree the problem makes no sense. I have brought this up before to Ken; m stands for molal while M sands for molar.

Chemistry
How much 2.5M HNO3. CaO + 2HNO3 => Ca(NO3)2 + H2O This is an acid/base reaction but in terms of the several types I think you are looking for double displacement.

Chemistry
I think I remember that dH I found on the web was 890 kJ/mol for dHcomb. I used that to calculate how much CH4 I had to start with and that's when I discovered you probably made a typo with that 10.0 mols you posted then. This problem is q for combustion is 4.319 kJ/mol x ...

Chemistry
I thought I did this for you a couple days ago and found you made a typo on the moles (instead of millimoles) CH4. What's giving you trouble?

chemistry
Why are you having trouble with this? pH = -log(H^+) Plug in pH, solve for H and use that and the last equation to solve for OH, then compare. (H^+)(OH^-) = Kw = 1E-14.

chemistry
dHrxn = (n*dHproducts) - (n*dHreactants) dSrxn = (n*dSproducts) - (n*dSreactants) Then dGrxn = dHrxn - TdSrxn If dGrxn is - the products are favored. Show your work if you gets stuck.

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

chemistry
See your posts above.

chemistry
See your post above.

chemistry step by step for me. Thank a lot
Is that 2m HNO3 or 2M HNO3?

math
4^8 = 6.5536E4 6.5536E4*8 = ?

chemistry
The acid is one of the pair with more H. The base is the one of the pair with fewer H. You name it; it can be a solvent.

chemistry
5.4% v/v means 5.4 mL/100 mL so in 435 mL solution there will be 5.4 x (435/100) = ? or (x/435)*100 = 5.4%

chemistry
Yes. That should be 10g solute.

chemistry
4% m/v means 4g solute/100 mL solution. So in 250 mL you would have 4 x 250/100 = ? Or another way is (x/250 mL)*100 = 4%

chemistry
a. Nope, that won't do it. M = mols/L solution. mols = grams/molar mass 335 mL = 0.335 L b. I'm confused by the question since HCl is a gas and not a liquid. So we need the density of the solution if that's what it is.

chemistry
I see your post below.

chemistry
You're right, it's probably wrong. If you will post the problem and your work I'll find the trouble.

chemistry
I assume all are gases. I assume initial H2O is 0. Initial (NO) = 0.100/2 = 0.050M Initial (H2) = 0.200/2 = 0.100M Initial (N2) = 0.0800/2 = 0.0400M ........2NO + 2H2 ==> N2 + 2H2O I......0.05...0.10....0.04..0 C......-2x....-2x....+x....+2x E...0.05-2x.0.10-2x.0.04+x..2x A...

chemistry
This is a bit out of my league but here is what I found on the web. There are other sites if you Google structure factor. structure factor

chemistry
1 amu = 1.6605E-24g

Math
698 miles x (1 gallon/18 miles) x (4 pts/gallon) = ?

Science
I assume the 30 degrees is the angle to the normal; also I assume you are neglecting the effects of the container holding the honey. n1*sin 30 = n2*sin 19.5 n1 is 1 for air. Solve for n2.

Chemistry
Didn't Bob Pursley do this for you? http://www.jiskha.com/display.cgi?id=1405592944

Science
The refractive index and whether the medium is more or less dense

Math
What's the problem? What's the question? You want a formula for what?

science
http://www.wisegeek.com/what-is-cardiovascular-homeostasis.htm http://www.mhhe.com/biosci/genbio/maderbiology/supp/homeo.html http://www.ehow.com/about_6326540_cardiovascular-system-maintain-homeostasis_.html

Chemistry
I assume your 0.907 is from 4.319kJ/C x (2.1C) = 9.07 kJ/10 mol = 0.907 kJ/mol. But you must correct for the wire and I don't think you've done that. The equation is CH4 + 2O2 ==> CO2 + 2H2O + heat When they say thermochemical reaction they may want dH = -? since it...

chemistry
2Na + Cl2 ==> 2NaCl Convert mols Na t mols NaCl. That's 3.0 mols Na x (2 mols NaCl/2 mols Na) = 3 mols NaCl g NaCl = mols NaCl x molar mass NaCl = about 175g (estimated). That is the theoretical yield(TY). The actual yield (AY) is 145.8. Note that the TY above is estima...

Science
KE = 1/2(m)(v^2) KE = 1/2 * 60 * 3^2 = ?

Chemistry
Don't you have some information about the increase in temperature?

math
let x = time it takes to walk home. (3/4)*x = 18 Solve for x.

math
Ms Sue gave you the answer worked out. If you want to do it algebraically, let x = the number, Then (x^4) + 4 = 26*10 Solve for x.

math
b = Bob's age now t = Tom's age now -------------- age now is b = 3t age in 12 years for t is t+12 = 15 Therefore, t now is 3 (that's 15-12 = 3) b age now is 3*3 = 9

Math
Is my face red. Circumference, which is what you want, is pi*diameter. I, unfortunately, gave you the formula for the area of a circle. Bad! I get an "F" for the day.

Math
If the diameter of the wheel is 45 cm then the radius is 45/2 = 22.5 cm and the circumference is pi*r^2. When the wheel makes one full revolution it will have traveled the circumference of the wheel.

math
One side is now 4*3 = 12 and the other side is 3*3 = 9 so the new perimeter must be 12+12+9+9 = ? The original perimeter is 3+3+3+3 = ? Now compare.

Chemistry
I assume you men 270 molal. 270 m means 270 mol/kg solvent. g NaCl = 270 x 58.5 (apprx) = estimated 16000 g (you need to go through the entire problem and redo the math; I've estimated all of these numbers. The mass of the solution is 1000 g solvent + 16000 g NaCl = about ...

CHEMISTRY
1)If we dissolve 0.03 mols HF in 1L H2O, we have prepared a solution that is 0.03M in HF. However, since HF is a weak acid, it dissociates(partly) in solution to HF + H2O ==> H3O^+ + F^- and the HF present as the molecule is decreased to 0.027M. 2) Any amount of HF in any a...

CHEMISTRY
For the second question and increase in the forward direction increases OH in the HPO4 rxn and that decreases pH. For the CO3^2- rxn the increase in the forward rxn decreases pH because H3O^+ is being used. For the initial post I don't know what you're asking.

math
Would that be 20*21/2 ?

chemistry
[275 mL/(725+275)] x 100 if you want it is %volume.

Science
I don't buy A. For example, I might observe that my clothes are wet and explain by saying I walked home in the rain. However I could have gotten wet by taking a shower with my clothes on. So I don't think just any explanation can go with just any observation.

Chemistry
I think the easy way to do b is to convert everything to millimols and use that to construct an ICE table. I think this way is easier than converting everything to final M. mmols HBz = mL x M = 250 x 0.125 = 31.25 mmols Bz^ = 250 x 0.147 = 36.75 mmols HCl added = 15.3 ...........

Chemistry
Are you sure about part a? I think an error is starting with 0.45M formic acid. Wouldn't you need to start with more formic acid to end up with 0.45M? If you used the HH equation for part b you should have come up with 3.64 and you're a long way from that. I used 3.75 ...

Chemistry
I thought we did all this yesterday. You worked the formula on your own and I showed you how to do the molar mass and molecular formula.

Chemistry
The procedure looks ok but the numbers don't.You must be punching the wrong buttons. The 0.00485 is really 0.004855 and I would round that to 0.00486 M (and that's M and not m) = 0.000198 x 1.92 = 0.000381 and molar mass is 0.242/0.000381 = ? Check my work.

Chemistry
You're right so far. 5.41E6 J = 5.41E3 kJ. molar mass Glauber's salt is 322 so here is what you have. 322 g salt absorbs 74.4 kJ. So how many g will it take to absorb 5.41E3 kJ. That will be 322 x (5.41E3 kJ/74.4 kJ) = ? g of the salt.

Chemistry
q = mass air(in g) x specific heat air x delta T Solve for q (which is delta H) Convert to g of the salt to give that delta H.

Chemistry
Glacial acetic acid is about 17.5M mL1 x %1 = mL2 x %2 mL1 x 17.5 = 120 mL x 25% mL 1 = ?

Chemistry
10% by volume means 10mL ethanol/100 mL solution. You want 150 mL so 10 mL ethanol x (150/100) = ? mL ethanol required.

chemistry
mols NaOH = M x L = ? mols vinegar = mols NaOH M vinegar = mols vinegar/L vinegar = ?

chemistry
You may be thinking that the double bond makes it a trigonal planar structure but when ethylene (with double bonds) is polymerized the double bond is broken and polyethylene consists of single bonds and that makes it tetrahedral. :-)

Chemistry
heat lost by Fe + heat gained by H2O = 0 [mass Fe x specific heat Fe x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute the numbers and solve for Tfinal H2O You may need to look up specific heat Fe and H2O if they aren't given in the p...

Chemistry
Nope. Liquid CAN'T be right. If you pour 100 mL water into a 100 mL container it is filled. If you pour the same volume f 100 mL water into a 500 mL container is will NOT be filled. So liquid can't be right. The answer of liquid is NOT using common sense. You KNOW the ...

Chemistry
I really wonder about this science bug with some. Many questions, like this one, is just common sense. Think this through and you'll have the answer. If you pour 100 mL water(a liquid) into a 100 mL beaker will it fill it? Will that same 100 mL water fill a 500 mL containe...

science
http://www.webelements.com/ Scroll down the table to find these elements and compare with the elements above them.

chemistry
mL1 x %1 = mL2 x %2 350 x 15 = mL x 9

Chemistry
121J/c/313 = ? J/g*C

Science
I believe the answer is B. Here is an example of weighing by difference and why it is a good method. Let's assume we know the mass of can accurately as 10g and a tennis ball accurately as 5 g. Now we use a scale in which we can't adjust the zero. Let's suppose at r...

CHEM
I'm assuming that 6.0m is a typo and you meant 6.0M.(There is a difference). mL1 x M1 = mL2 = M2 mL1 x 6.0M = 110 mL x 0.500M

Chemistry
A factor converts any unit to any other unit. The factor used depends upon which unit you have and which unit you want. For example. A. There are 10 mm to 1 cm so the conversion factor is 10mm/1cm or you can write it the other way as 1 cm/10mm. 8.43 cm x factor = ? mm Now we d...

Chemistry
No, if pi = MRT then M = pi/RT M = 0.00543/(0.08205*301) = about 0.000220M or mols/L. M = mols/L mols = M x L = 0.000220*1.37L = about 0.000301 mols = grams/molar mass or molar mass = grams/mols = 0.325/0.000301 = ? Note, however, that even if what you proposed were correct th...

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