Wednesday
April 1, 2015

Posts by DrBob222


Total # Posts: 48,035

Chemistry
:-). Difficult for some, yes. Dull? Never.
January 17, 2015

Chemistry
I'm a chemist and I would tell you that you're in for an exciting course; however, not every one feels that way about chemistry. Instead you must wait and see for yourself. There is some that you can memorize and if you can memorize things easily you can make it ...
January 17, 2015

Chemistry
#1. We are here to help. #2. I have no idea why you think there is an attitude problem. I'm sorry I couldn't answer your question exactly but as I stated I simply don't understand the question completely. I hoped that whatever I posted would trigger a response from...
January 17, 2015

Chemistry
I see you still think changing names helps. Here is what I think. I believe you are to calculate the pH of various solutions from pH 1 to pH 13 but I don't understand the phrase "pH titration". And I don't know how the volume fits in. I can show you how to do...
January 17, 2015

Chemistry
Would you check your problem please? Usually titration curves are done with pH vs volume. One then chooses volumes to make the curve.
January 17, 2015

Chemistry
Charlotte, Maddie, Quincy et al. I have answered this below. Changing screen names is confusing. you get better results if we can keep can follow you. Changing screen names doesn't get your questions answered any faster; in fact, it may slow the answers.
January 17, 2015

Chemistry
I have already answered this below. You may repost here if you have a follow up; it will be easier to find here than below.
January 17, 2015

Chemistry
I can't decipher what you have because of the spacing and extra lines. Do this. Write the atomic number FIRST, then the element symbol, then the mass number. For example, Radon 222 would be written as 86Rn222; the alpha particle (He nucleus) is 2He4, etc. I think you may ...
January 17, 2015

chemistry
Will you please check your post. I'm have a problem with the "higher" part. I was under the impression that C 14 content DECREASED with time, not increased.
January 17, 2015

Chemistry
Citric acid has three ionization constants; i.e., k1, k2, and k3. pK1 = 3.13 pK2 = 4.76 pK3 = 6.39 Your tables may not agree exactly; use the numbers in your text/notes. The pH you want in the solution should be as close as possible to one of the pKa values; therefore, I would...
January 17, 2015

Chemistry
Personally I think you are out of luck on someone doing this for you. Standardization of the NaOH is a chapter in itself followed by another chapter on reading the buret, preparing the buret, how to standardize the pH meter, etc. Surely you already know how to do the basics; ...
January 17, 2015

Chemistry
Distribution coefficients = Ko/a so large K values occur as the result of higher solubility in the organic phase than in the aqueous phase. In contrast, lower K values result from a higher concentration in the aqueous phase than in the organic phase. Therefore, ......can you ...
January 17, 2015

Chemistry
I would point out that a 37% w/w solution has a density of 1.19 so I wonder if you have incorrectly labeled it as v/v. It makes little difference which is true, if you don't give a volume of the hcl solution used there is no way to calculate the final concentration.
January 17, 2015

Chemistry
I don't believe the pH is absolutely necessary; however, if it is wouldn't it be pH = pKa for TRIS. Since these are equal amounts of equal concentrations then (base) = (acid) and pH = pKa + log 1 = pKa. Prepare the base by the following: mols TRIS base = M x L = 0.100 ...
January 16, 2015

Chemistry
It's a redox (oxidation-reduction) reaction and it requires an acid solution. H2SO4 usually is the acid used because HCl has complications with the chloride ion.
January 16, 2015

chemistry
2Na + Cl2 ==> 2NaCl 5.5 mols Na x (2 mols NaCl/2 mols Na) = 5.5 mols Na x 2/2 = 5.5 mols NaCl. Convert to grams. g = mols x atomic mass.
January 16, 2015

chemistry
K2CO3 + 2HNO3 --> 2KNO3 + H2CO3 then the H2CO3 decomposes as H2CO3 --> H2O + CO2 I would name that first reaction as double replacement.(some call it double displacement). Usually this reaction is written all at once as K2CO3 + 2HNO3 ==> 2KNO3 + H2O + CO2 and that ...
January 16, 2015

Science
yes
January 16, 2015

chemistry
volume of water to be removed is 5000 cm x 2500 cm x 3.2 cm = approx 4E7 cc Convert to ? L Then 5.0 L/sec x #sec = ? L. Sole for #sec.
January 16, 2015

clarify--SCIENCE
Please proof your post and make changes to make it make sense. What's AgNOS? "required 26.50 mL and Ag of AgNO3 = 0.008700g" makes no sense at all.
January 16, 2015

clarify--Chemistry - PLEASE HELP!!!
Is all 5.0 g N2O transferred to to the whipped cream container? And what is the volume of the balloon?
January 15, 2015

Chemistry
Devron is correct; this is a combustion reaction/problem.
January 15, 2015

Chemistry
T is constant so we don't need to worry about that so let's just use 300 K for it. The reaction is 2C2H2 + 5O2 ==> 4CO2 + 2H2O For the larger 7 L tank filled with O2 at a pressure of 145, what is n? Use PV = nRT and calculate n = number of moles O2. Now use the ...
January 15, 2015

CHEMISTRY
And how many books do you want me to write about these topics? If you will tell me what your trouble is in answering these I shall be glad to help you through them. What is the sticking point of each?
January 15, 2015

chemistry
Pb(NO3)2 + 2KI ==> PbI2 + 2KNO3 mols KI = grams/molar mass = ? mols PbI2 = 1/2 mols KI mass PbI2 = mols PbI2 x molar mass PbI2
January 15, 2015

Chemistry
No H bonds in CH4. NH3 is the answer.
January 15, 2015

Chemistry
Use the conversion factor. 10,000 m x (1.09 yds/1 m) = ?
January 14, 2015

Chemistry
Jefferson, what trouble are you having with limiting reagent problems. When you've worked one you've worked 98% of them. Devron showed you how to do one just a short time ago and I went through one in detail with you last night.
January 14, 2015

Chemistry
Very good. I would offer these thoughts (not suggestions). First I looked up the molar mass of Na2CO3 and obtained 105.989 but we may not have used the same sets of numbers. Second, the number of significant figures you have used is not consistent. If that 1.234 is ok then you...
January 14, 2015

Chemistry
Yes, 2 is the first equivalence point See this graph. Note the first equivalence point is HUGE compared to the third.https://www.google.com/search?q=image+H3PO4+and+NaOH&tbm=isch&tbo=u&source=univ&sa=X&ei=HCG3VJTBFJGTNuGXguAI&ved=0CCIQsAQ&biw=1024&bih=609#imgdii=_&imgrc=...
January 14, 2015

chemistry
Damon showed you how to work the problem a short way. The answer to your question is yes, it is 3*95 = ?
January 14, 2015

Chemistry
91 what? (P1V1/T1) = (P2V2/T2)
January 14, 2015

science Help
B, C and D are pure made up ridiculous answers.
January 14, 2015

Science
So half of it will be gone in 6 hours. Another half of it will be gone in 12 hours. You started with 2g. At the end of 6 hrs there will be 1 g. At the end of 12 hours there will be 1/2 g left? right?
January 14, 2015

Science
I think C is right. Speed is a scalar quantity(number only); i.e., magnitude but no direction. Velocity is a vector quantity; i.e., a magnitude with a direction.
January 14, 2015

Science
I don't think so.
January 14, 2015

Science
I agree with both.
January 14, 2015

Chemistry
This is a limiting reagent problem just like the ones that Devron worked for you this morning. 2C8H18 + 25O2 ==> 16CO2 + 18H2O That should get you started. Step 1. convert grams to mols. mols = grams/molar mass Step 2. Using the coefficients in the balanced equation, ...
January 14, 2015

Science
Radiatioin can travel through space. Conduction travels through solids and to some extent liquids.
January 14, 2015

Chemistry
Then you don't understand the question because that equation tells you everything you ever wanted to know and then some. Here is what it says. It tells you that if 4 mols Fe reacts with 3 mols O2 it will produce 2 mols Fe2O3 and 1652 kJ of heat. So the first question is 4 ...
January 13, 2015

Chemistry
I would like to add here that you had the right idea if you had followed through. Your statement that ClO is losing O is ok but since it is LOSING O is must be reduced. Gaining O is oxidation. Of course if O is nowhere in the oxidation it's tough to use that as a ...
January 13, 2015

science
When I do work, like running 1 mile in less than 4 minutes, you see heavy breathing, faster breathing, sweating, much higher heart rate, muscles tired, etc. So the work I expend in running that mile shows up as increased CO2 in the air, faster metabolism, aching muscles, etc. ...
January 13, 2015

Chemistry
IO3^- + 5I^- + 6H^+ ==> 3H2O + 3I2 I2 + 2S2O3^2- ==> SrO5^2- + 2I^- Check those equations; I'm trying to remember it instead of working it out. mol IO3^- = M x L = 0.0214 x 0.010 = ? 1 mol IO3^- = 3 mols I2 1 mol I2 = 2 mols S2O3^- Therefore, 1 mol IO3^- = 6 mols ...
January 13, 2015

chemistry
76.7g PCl3 x 0.832 = ?g PCl5
January 13, 2015

Chemistry
2 Mg (s) + O2 (g) -> 2 MgO (s) Mg on the left must go to Mg on the right but the Mg on the right is an ion. It has a charge of 2+; therefore, 2Mg --> 2Mg^2+ + 4e O2 + 4e ==> 2O^2-
January 13, 2015

Chemistry
Tell me what the problem is with this.
January 13, 2015

chemistry
Lewis, I don't have the slightest idea what you're talking about. Please clarify.
January 13, 2015

chemistry
You're assuming the Kool-Aid drink is pure sugar. Then grams sucrose = molarity x liters x molar mass = 0.346 x 0.200 x 342 = ? g sucrose.
January 12, 2015

Chemistry
H2 + 1/2 O2 = H2O Look up the delta Ho formation for water and change the sign in the table. That will give you H2O ==> H2 + 1/2 O2 in kJ/mol
January 12, 2015

Chemistry
This is a limiting reagent (LR) problem because amounts are given for BOTH reactants. You need to find the arrow key and use it; otherwise we don't know where the reactants end and the products start. 2Mg(s) + O2(g) 2MgO(s) mols Mg = grams/molar mass mols O2 = grams/molar ...
January 12, 2015

DrBob222 my previous question
Here's a link. You can respond here if you wish. http://www.jiskha.com/display.cgi?id=1421108421
January 12, 2015

DrBob222 my previous question
Let me look. I will answer there.
January 12, 2015

Chemistry
q diamond = mass diamond x specific heat diamond x delta T q H2O = mcdT
January 12, 2015

chemistry Drbobz222
In the equation for that process we had 2AgNO3 + CaCl2 ==> 2AgCl + Ca(NO3)2 You convert anything to anything using the coefficients in the balanced equation. Let's just suppose you had 0.1 mol CaCl2 (I don't remember the numbers) so we want to convert 0.1 mol CaCl2 ...
January 12, 2015

Chemistry
You have a limiting reagent (LR) problem here because amounts are given for BOTH reactants. NaOH + HCl ==> NaCl + H2O mols NaOH = grams/molar mass= ? mols HCl ==> grams/molar mass = ? Using the coefficients in the balanced equation, convert mols NaOH to mols NaCl. Do the...
January 12, 2015

chemistry check my answer
And I didn't get the link posted but here it is. http://www.jiskha.com/display.cgi?id=1421101733 I get almost 257 but the number if have is 0.25644 L which I would round to 0.256. I don't know what atomic mass you used for Ca. I went back and checked and used 40.078 ...
January 12, 2015

chemistry check my answer
And I didn't get the link posted but here it is. http://www.jiskha.com/display.cgi?id=1421101733 I get almost 257 but the number if have is 0.25644 L which I would round to 0.256. I don't know what atomic mass you used for Ca. I went back and checked and used 40.078 ...
January 12, 2015

chemistry check my answer
ok. I found it and I'm copying it here. However, I don't see an answer.
January 12, 2015

chemistry check my answer
Yes. Can you give me a link? I don't think you can post a link so look at the link and give me the time and date in the line. I can find it that way. Also the name/author.
January 12, 2015

chemistry check my answer
Almost. It's 0.19?. Don't throw that last digit away. You have three places in the volume and three places in the molarity; therefore, you're allowed three places in the answer. You're throwing a perfectly good number so you should keep it. I have 0.1949538 ...
January 12, 2015

chemistry check my answer
The problem states 17.5 mL H2SO4 and not 32.5. The 32.5 mL is volume NaOH in the problem. If I replace the first 32.5 with 17.6 your set up is right. Then multiply 17.6 x 0.180 x 2/32.5 I don't get 0.36 but I do get the right answer. You may be punching it in on the ...
January 12, 2015

chemistry check my answer
I don't think so. Did I post the wrong instructions? If you will post your work I will look at it.
January 12, 2015

Chemistry
dGorxn = (n*dGo products) - (n*dGo reactants
January 12, 2015

chemistry am i right
right.
January 12, 2015

chemistry
How did you convert mols AgNO3 to mols AgCl?
January 12, 2015

chemistry
You use the coefficients in the balanced equation to convert anything you wish. For CaCl2 to mols AgCl it is ?mols CaCl2 x (2 mols AgCl/1 mol CaCl2) = ?mols CaCl2 x 2/1 = ?mols AgCl.
January 12, 2015

chemistry
You have a limiting reagent problem here. You know that because amounts are give for BOTH of the reactants. 2AgNO3 + CaCl2 ==> 2AgCl(s) + Ca(NO3)2 mols AgNO3 = M x L = ? mols CaCl2 = M x L = ? Using the coefficients in the balanced equation, convert mols AgNO3 to mols AgCl...
January 12, 2015

chemistry
molecular: Ca(OH)2(aq) + 2HNO3(aq) ==> Ca(NO3)2(aq) + 2H2O(l) ionic: Ca^2+(aq) + 2OH^-(aq) + 2H^+(aq) + 2NO3^-(aq) ==> Ca^2+(aq) + 2NO3^-(aq) + 2H2O(l) NET ionic: Just cancel the ions that are common to both sides to leave 2H^+(aq) + 2OH^-(aq) ==> 2H2O(l)
January 12, 2015

Chemistry
Refer to your skillet problem.
January 12, 2015

Chemistry
q = heat removed = mass Fe x specific heat Fe x (Tfinal-Tinitial)
January 12, 2015

chemistry
mols ZnCO3 = grams/molar mass Then M = mols/L solution You know M and mols, solve for L.
January 12, 2015

Math
I don't think so.
January 12, 2015

chemistry
Ca + 2HCl --> CaCl2 + H2 mols Ca = grams/atomic mass mols HCl = twice that since 1 mol Ca = 2 mols HCl Then M HCl = mols HCl/L HCl and this can be arranged to L HCl = mols HCl/M HCl which let's you solve for L HCl.
January 12, 2015

chemistry
You made a typo: that's Sr(NO3)2 Molecular: Li2SO4(aq) + Sr(NO3)2(aq) ==> SrSO4(s) + 2LiNO3(aq) ionic: 2Li^+(aq) + SO4^2-(aq) + Sr^2+(aq) + 2 NO3^-(aq) ==> SrSO4(s) + 2Li^+(aq) + 2NO3^-(aq) NET ionic: Just cancel the ions common to both sides to leave you with Sr^2+(...
January 12, 2015

chemistry
M is the molarity. L is liters. I should have used the cap L and not the lower case l. There is no accepted abbreviation for molar mass.
January 12, 2015

chemistry
2HNO3 + Ca(OH)2 ==> Ca(NO3)2 + 2H2O mols Ca(OH)2 = M x l = ? mols HNO3 = twice mols Ca(OH)2 [Note the coefficients in the balanced equation] M HNO3 = mols HNO3/L HNO3 = ?
January 12, 2015

Chemistry
H2SO4 + 2NaOH ==> Na2SO4 + 2H2O mols H2SO4 = M x L = ? mols NaOH = twice that of H2SO4.[Note the coefficients in the balanced equation.] M NaOH = mols NaOH/L NaOH
January 12, 2015

Chemistry
You need to find the arrow key and use it. Without an arrow how do we tell the reactants from the products. Fortunately I know where it is but in the future remember this tip. dHrxn is -1267 kJ and that is for 4*17 = 68g NH3. YOu want to know dH for 7 g NH3. That's -1267 ...
January 12, 2015

Chemistry
q1 = heat needed to raise T of solid ice at -1.383 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice; i.e., change phase from solid to liquid. q2 = mass ice x heat fusion q3 = heat needed to raise T of liquid water from zero C to 85....
January 12, 2015

Chemistry
I'm assuming the indicator was something in the acid range, say change pH about 4 to 5 which would mean CO3^2- was titrated all the way to H2O and CO2. K2CO3.xH2O + 2HCl ==> H2O + CO2 + xH2O _ 2KCl mols HCl. Subtract from each other and take the average. That's 9.2 ...
January 12, 2015

Chemistry
What indicator did you use?
January 12, 2015

chemistry
I have seen that algebraic method. I've even used it a few times but by an large it's more trouble than it's worth. I don't like it that much. For these simple equations (the above one is a simple one) it takes less than half a minute. If I used the algebraic ...
January 12, 2015

chemistry
No yours is not right. You have 9 Fe on the left and only 2 on the right. You have 2Al on the left and 4 on the right. The oxygen atoms don't balance wither. Try this. 3Fe3O4 + 8Al ==> 4Al2O3 + 9Fe I ALWAYS check these things to make sure they are right. Follow me. 9 Fe...
January 12, 2015

Chemistry
I would convert 30.50 kg to grams. mols HCl = grams/molar mass Then M = mols/L Since HCl is 100% ionized, (H^+) = (HCl) and pH = -log(H^+) Then pH + pOH = pKw = 14. Use this to calculate pOH. Finally, pOH = -log(OH^-) and calculate OH^-.
January 12, 2015

ap chemistry
mass dehydrated sample is mass sample + container after heating - mass sample + container before heating
January 12, 2015

chem
I don't agree with the equation because you can't isolate CaO. It immediately reacts with H2O to form CaOH)2 as I've indicated in the equation below. However, none of that changes the stoichiometry of the equation and 1 mol Ca still produces 1 mol H2 gas. Ca + 2H2O...
January 12, 2015

chemistry
55.5 mols/L
January 12, 2015

Chemistry (Acid-Base)
Look up the density of water at 25C and use that to calculate the mass of 1000 mL. Ifound density at 25 C = 0.99705 g/mL; therefore 1000 mL has a mass of 997.05g.Then mols H2O = grams/molar mass = 997.05/18.015 = about 55.35 M
January 12, 2015

Chemistry (Acid-Base)
I must confess that I've never heard the term "protonation constant" used. Logic tells me this might be the reciprocal of Ka, the dissociation constant but I don't know that. Can you shed some light? If we can define what the protonation constant is I can help.
January 12, 2015

Science
http://en.wikipedia.org/wiki/Tide
January 12, 2015

chemistry
Al2O3. mols Al2O3 = grams/molar mass = ? Since there are two Al atoms in a molecule of Al2O3, twice that will be mols Al. Then remember that 1 mol of Al contains 5.02E23 atoms Al.
January 11, 2015

Chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. Fe3O4 + 2C ==> 2CO2 + 3Fe mols Fe3O4 = grams/molar mass = ? mols C = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe3O4 to mols Fe. Do ...
January 11, 2015

chemistry college
This is a direct relationship and I think that is easier to use here than going through the p = KcC or C = KpP. 0.169 g/100 x (43,000/760) = ?
January 11, 2015

Chemistry
First, note that you can't throw all of those numbers after 0.0049 away. You have 4 places in 0.4835 and you should have AT LEAST 4 in the answer. I usually carry one more place and round at the end. Ca^2+ + EDTA ==> Complex mols EDTA = mols CaCO3 Then M EDTA = mols/L ...
January 11, 2015

Chemistry
http://www.jiskha.com/display.cgi?id=1421013794
January 11, 2015

Chemistry
3 x that for K 1 x that for P 4 x that for O
January 11, 2015

chemistry
28000 = mass ice x heat fusion. Subsitute heat fusion in calories/g and solve for mass of ice in grams.
January 11, 2015

Chemistry
When gases are involved one may use stoichiometry as if volume = mols. 800 cc O3 x (3 mols O2/2 mols O3) = 800 x 3/2 = ? cc O2
January 11, 2015

chemistry
.........N2(g) + 3 H2(g) ⇀↽> 2 NH3(g) E.......3.1M......0.8M..........x K = 5.2E-5 = (NH3O^2/(N2)(H2)^3 Plug the equilibrium numbers into Keq and solve for (NH3) in mol/L. Convert to mols in 10 L and convert that to grams.
January 11, 2015

CHEM
What's your problem. Write the Keq expression, substitute the equilibrium numbers in the problem, and solve for Keq. If you still can't do it explain fully what you don't understand.
January 11, 2015

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