Friday
July 31, 2015

Posts by DrBob222


Total # Posts: 49,593

what changes?--Chemistry

July 30, 2015

chemistry
Surely you don't mean 0.01 g/mL density. I might believe 1.01. Steps to follow after you know the density. mass solution = 1000 mL x density = ? mass solution - 10 g H2SO4 = ? g H2O Then mols H2SO4 = 10/molar mass = ? mols H2O = grams/molar mass = ? XH2SO4 = mols H2SO4/...
July 30, 2015

Chem
I'm not sure what you want when you say describe. Heat will flow from the 59 C metal to the 25 C water. The metal will cool; the H2O will warm. The final T of both will be less then 59 and greater than 25 You can calculate the final T of both by substituting and solving ...
July 30, 2015

Physical sciences
You need to provide more details. This seems to just part of the problem.
July 30, 2015

Chemistry
Carbonate is -2 so Ag must be +1 each.
July 29, 2015

Chemistry
I responded at the original post. I was busy answered those million questions posted by Mindy so it took a little while to get back to your question.
July 28, 2015

Chemistry
See this link. http://www.jiskha.com/display.cgi?id=1438134034
July 28, 2015

Chemistry
So show what you did and I shall be happy to check it for you. First, however, look at the previous problem. This problem is actually the same as the previous problem but worked twice in the same problem. Have you identified the limiting reagent?
July 28, 2015

Chemistry
I don't buy Paula's answer.
July 28, 2015

Chemistry
mols CCl4 is correct at 104. Now you want to go to step 2 and convert mols CCl4 to mols CS2. That is done this way using the coefficients in the balanced equation. 104 mols CCl4 x (1 mol CS2/1 mol CCl4) = ?
July 28, 2015

Chemistry
The problem tells you the reactants and products. Copy those down, then balance it. CS2 + 3Cl2 ==> CCl4 + S2Cl2 Then the problem part. 16 kg = 16,000 g mols CCl4 = grams CCl4/molar mass CCl4 = ? Using the coefficients in the balanced eaquation, convert mols CCl4 to mols CS2...
July 28, 2015

Chemistry
I did the same thing as Enrique with initial (H2) = 0.510; (I2) = 0.173; (HI) = 0, did the set up and my final concentrations are not close to any numbers listed. You know the negative numbers can't be right.
July 28, 2015

Chemistry
I don't think so. 4.65 g H2 x (1 mol/2g) x (1/4.55L) = not 0.0037 or perhaps I've misinterpreted your work. And what's with the - signs?
July 28, 2015

Chemistry
Actually, I think Enrique is talking about the first equilibrium. After that, you will need to set up a second one with the added 1.25 M I2 and run through a second set of calculations. Post your work as far as you can get and explain what you don't understand if you get ...
July 28, 2015

chemistry
PV = nRT
July 28, 2015

chemistry
No. I see P1 of 567 and V1 of 136. On the right I see 421 and all of those are in the right place. Where did the 183 come from? That's what you're solving for and is the answer. The way you have it set up there is no unknown and I have no idea how you ended up with 4,...
July 28, 2015

chemistry
P1V1 = P2V2. You can use this because T is constant. However, since T is given, you can use (P1V1/T1) = (P2V2/T2) and come out with the same answer.
July 28, 2015

chemistry
Always start with a balanced equation. You have that. Convert 54.92 g KNO3 to mols. mol = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KNO3 (what you have) to mols of what you want (mols O2). Then convert that to volume using PV = nRT. ...
July 28, 2015

chemistry
PV = nRT and solve for V in L.
July 28, 2015

chemistry
I would use (P1/T1) = (P2/T2), substitute and solve for T2. P1 = 1.248 atm T1 = 273 + 24.8 = ? P2 = 2.410 atm T2 = ? We don't need to worry about V because that doesn't change.
July 28, 2015

chemistry
No expressions given. But that's just a little algebra. I'll be glad to check you work.
July 28, 2015

chemistry
0.731 atm x (760 mm/1 atm) = ? Note how the atm unit cancels (the unit you don't want) so the answer comes out in mm (the unit you want to keep).
July 28, 2015

chemistry
The general gas law of PV = nRT can be modified to P*molar mass = density*RT. You can also work it the long way. PV = nRT and solve for n to find mols. Use 1L for volume. Then n = grams/molar mass. You know n and molar mass, solve for grams and that will be g/L since you used ...
July 28, 2015

chemistry
(P1V1/T1) = (P2V2/T2) T must be in kelvin.
July 28, 2015

Chemistry
(V1/T1) = (V2/T2) Remember T must be in kelvin.
July 28, 2015

Chemistry
The easy way to do this is to recognize that volume is proportional to mols of gas at the same T and P or (n1/v1) = (n2/v2) but an equally easy, but more work is to assume some value for T (any convenient numbers will work) and use PV = nRT, substitute the numbers and solve ...
July 28, 2015

Chemistry
Correct. Good work.
July 28, 2015

Chemistry
Do you know that STP stands for standard temperature and pressure. Standard T is 273 K and standard pressure is 1 atmosphere. Use (P1V2/T1) = (P2V2/T2) Don't forget to change degrees C to kelvin. Post your work if you run into trouble.
July 28, 2015

Chemistry
See your previous posts. Same formula, different numbers and different unknown.
July 28, 2015

Chemistry
See your water post just before this. Same formula, different numbers. Post your work if you get stuck or don't understand something.
July 28, 2015

Chemistry
No. What did you multiply? mass H2O = 550 g. specific heat H2O = 4.184 J/g*C Tfinal = 18 C Tinitial = 12 C
July 28, 2015

Chemistry
q = joules needed = mass H2O x specific heat H2O x (Tfinal-Tinitial)
July 28, 2015

chemistry
Your first post was answered. You need to look for the answer before posting a duplicate.
July 28, 2015

science
The water will float on the unknown liquid.
July 28, 2015

organic chemistry
I don't understand the problem. There is a cis-2-pentene and a trans-2 pentene. If the H atoms are on the same side it is cis and if they are on the opposite sides trans. Read about it here. https://en.wikipedia.org/wiki/Pentene
July 28, 2015

science
https://www.google.com/search?q=isa+relationshii&ie=utf-8&oe=utf-8
July 28, 2015

Nat Sci
I think you are right. Tectonic plates are the actual plates themselves while plate tectonics is the science (or the name of the science) of the process.
July 27, 2015

science
I agree with San.
July 27, 2015

Chemistry
You really don't know from the way the problem is stated; however, I assume the problem means "if the exact amount of reagents are mixed to produce the 2.89 g Ag2C4O4 and neither reagent is left". 2AgNO3 + Na2CrO4 ==> Ag2CrO4 + 2NaNO3. mols Ag2CrO4 = grams/...
July 27, 2015

chemistry
You want how many mols? That's M x L = mols. Then mols = grams/molar mass. YOu know mols and molar mass, solve for grams.
July 27, 2015

science
http://www.physics.org/article-questions.asp?id=65
July 27, 2015

Chemestry
1. Ca has a oxidation state of +2 on the left and zero on the right. Na is zero on the left and +1 on the right. Oxidation is the loss of electrons; reduction is the gain of electrons. Which lost and which gained and you have the answer. 2. What's your problem with this ...
July 27, 2015

chemistry
H2SO4 + 2NaOH ==> 2H2O + Na2SO4 mols NaOH = M x L = ? Using the coefficients in the balanced equation, convert mols NaOH to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols ad M, solve for L. Convert to cm^3 if needed.
July 27, 2015

m.e.i.pampore
The titration of a weak acid and strong base gives a pH at the equivalence point of between 8 and 10. The k1 for oxalic acid is fairly strong but hard to separate from k2. So you want an indicator that will change about 8-10. Phenolphthalein is suitable for that.
July 27, 2015

chemistry
How many mols is 3.50 g KI? That's mols = grams/molar mass = 3.5/approx 366 = approx 0.021 mols. You want to dilute the 5.95 to what volume? The new concentration of the 5.95M solution will be 5.95 x (0.047/y) = ? where y is the volume to which it is diluted but you don&#...
July 26, 2015

organic chemistry
http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Valence_Bond_Theory/Resonance/Delocalization_of_Electrons
July 26, 2015

Chemistry
Some sites to choose from. Read, read, read. https://www.google.com/search?q=errors+in+colorimetry&ie=utf-8&oe=utf-8
July 26, 2015

Chemistry
mols Mn = grams/atomic mass mols C = grams/atomic mass Now find the ratio to each other with the smallest being 1.00. The easy way to do that is to divide the smaller number by itself (which makes it 1.00), the divide the other number by the same small number. Round to whole ...
July 25, 2015

Chemistry
mols NaOH = grams/molar mass = ? Then M = molarity = mols/L solution. You know mols and L, solve for M. That will be the OH^- since NaOH is a strong electrolyte. Convert to H^+ (H3O^+) with (H^+)(OH^-) = Kw = 1E-14 You know Kw and OH, solve for H..
July 25, 2015

informatic
Do you want a flow chart or a conversion chart?
July 25, 2015

chemistry
L is liters (or litres), not lt. 1 mole of a gas occupies 22.4 L at STP. So how many moles do you have? That's 5.8 L x (1 mol/22.4 L) = approx 0.25 but you need a more accurate answer than that. Then mols = grams/molar mass. You have mols and grams, solve for molar mass.
July 25, 2015

org chem
One reason is that glycerol boils close to 300 C and that is much higher than water. Boiling points would be much hard to obtain if they were above 100 and water was used. Oil is a good alternative for both melting and boiling point determinations.
July 25, 2015

Chem
q1 = heat needed to heat ice at -24 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tf is zero and Ti is -24 q2 = heat needed to change solid ice at zero to liquid water at zero. q2 = mass ice x heat fusion. q3 = heat needed to heat water at zero to ...
July 24, 2015

chemistry
5.469 g = mass MgSO4 + xH2O -2.671 g = mass MgSO4 -------------- 2.798 g = mass H2O mols MgSO4 = 2.671/molar mass = ? mols H2O = 2.798/molar mass H2O = ? Now find the ratio for 1 mol MgSO4. The easy way to do that is to divide mols MgSO4 by itself (which automatically gives ...
July 23, 2015

chem 101
2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols H2SO4 = M x L = ? Using the coefficients in the balanced equation, convert mols H2SO4 to mols NaOH. That's mols H2SO4 x (2 mols NaOH/1 ml H2SO4) = ? Then M NaOH = mols NaOH/L NaOH. YOu know M NaOH and mols NaOH, solve for L NaOH and ...
July 23, 2015

science: chemistry
HC2H3O2 = HAc moles HAc = M x L = 2.6 x 1 = 2.6 Let x = mols OH to be added. ..........HAc + OH^- --> Ac^- + H2O I.........2.6....0.......0.......0 add..............x............... C.........-x....-x.......x.......x E.........2.6-x..0.......x.......x I don't know what ...
July 23, 2015

science: chemistry
Convert 47.4 g C2H4NH3Cl to mols. mols = grams/molar mass = ?. Since that is in 1 L solution, that will be the molarity. This is the acid. You have 0.68 M solution of C2H4NH2 which is the base. Substitute into the Henderson-Hasselbalch equation, and solve for pH.
July 23, 2015

chemistry
I'm inclined to think gravimetric analysis would be better. Six grams is measured easily and accurately as is 100 mL. In most cases colorimetric analysis works best for dilute solutions; therefore, any small error in measurement would be magnified when converted to the ...
July 23, 2015

chem
right. and I tried to get 0.08206 out of 1/273 but no matter how hard I tried it wouldn't work. But 22.4/273 = 0.08205 or 22.404/273 = 0.08206 which is the number usually quoted. I expect a mathematician will tell me that 22.404 is a lot of s.f. that probably don't ...
July 22, 2015

chem
I think there is an extra 273 (on the left side) in this solution that doesn't belong there. PV = nRT n = PV/RT n = 1.2*5.25/(0.08206*299) n = 0.26
July 22, 2015

Chemistry
ln(k2/k1) = Ea(1/T1 - 1/T2)/R ln(1.5E-3/3.46E-5) = 195000(1/308 - 1/T2)/8.314 Solve for T2.
July 22, 2015

Chemistry
When the object is of irregular shape; ie., can't be measured with length, width, height.
July 22, 2015

Chemistry
KOH + HCl ==>H2O + KCl mols HCl = M x L = ? mols KOH = M x L = ? mols HCl = mols KOH so the reaction is exactly neutralized and mols H2O prduced is 0.009. q rxn = mass solution x specific heat solution x delta T The problem doesn't say what the density is; I assume we ...
July 22, 2015

Chemistry
heat capacity = specific heat x g = ? That's 0.14 J/g*C x 83 g = ? J/C
July 21, 2015

Chemistry
q = mass Zn x sp.h. Zn x (Tf-Ti) Substitute and solve for mass Zn.
July 21, 2015

Chemistry
heat lost by Cu + heat gained by Fe = 0 [mass Cu x specific heat Cu x (Tf-Ti)] + [mass Fe x specific heat Fe x (Tf-Ti) = 0 Substitute and solve for mass Fe Post your work if you get stuck.
July 21, 2015

Chemistry
q1 = heat needed to warm ice at -5.2 C to zero. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tf is zero and Ti is -5.2. q2 = heat needed to change phase from solid ice at zero to liquid water at zero. q2 = mass ice x heat fusion q3 = heat needed to warm liquid ...
July 21, 2015

New delhi
20% mens 20g amino acid in 100 g solution. mols amino acid = grams/molar mass. You don't say what amino acid it is so look it up and use the molar mass. Then use density to convert 100 g solution to volume. Finally, substitute into M = mols/L solution. Post your work if ...
July 21, 2015

Chemistry
Write the Arrhenius equation for me then show what you have substituted for each symbol.
July 21, 2015

Chemistry
Substitute into the Arrhenius equation.
July 21, 2015

Math
I agree with 15.
July 21, 2015

Chem
I didn't go through the math but assume all of that is ok then the total q needed is 40711 J. Frankly that doesn't look right to me because the step making steam at 100 is higher than that I think. Look up the heat of combustion of gasoline--I've said that three ...
July 21, 2015

Chem
I think you meant it correcly but said it wrong. You want to replace the 1.86 with 2.01.
July 21, 2015

Chem
1.86 is the molal freezing point constant for water. Google "specific heat steam" without the quotation marks to find the specific heat steam. In fact, with a little bit of digging you probably could find pieces of this problem worked somewhere on Google.
July 21, 2015

Chem
450x4.184(100)188280 I don't know what this is. It isn't anywhere in the above. It should be 450 x 4.184 x (100-21) = ? if it's the heat needed to raise the temperature of the water from 21 to 100. 450x4.184(110-100)= 18828 I assume this is supposed to be the heat...
July 21, 2015

typo--Chem
I made a typo on your "cup" line. Here is the correct copy. The 100 C should be 110 C. 47(110-21)=4183 This is the heat needed to raise the T of the cup from 21 to 100.
July 21, 2015

Chem
As I said before, this is a multi-step problem. What you're doing is calculating how much heat is needed for each of the steps in getting Cu from 21 to 110 and in getting the water and the cup from 21 to 110. The next part of the problem then is to calculate the amount of...
July 21, 2015

Chem
The part you have is ok but you've posted only part of what you need. First, I assume that 21O C and 110O C are 21o C and 110o C. Now you have Cu wire + water as a system. You need to calculate q for the copper wire and add to q from the water and add to q for the cup and ...
July 21, 2015

Chem
See your previous post under Cynthia.
July 21, 2015

Chemistry II
CpxmassxTf-Ti (2.06)(275)(0-(-25))=14162.5 This step is perfect. Good work! 333J/100x14162.5 = 47161.125 I don't understand this step. You should be melting all 275 g of the ice so it should be 333 J/g x 275 g = ? J for the melting step. Now you want to raise the ...
July 21, 2015

Chemistry II
We prefer you stick to the same screen name. This is a many step problem. How much have you done and exactly what do you not understand.
July 21, 2015

Chemistry
No. I suggest you look up the Arrhenius equation and use it. Where is Ea? Where is R? Which R will you use? You have T1 and T2 right but no where in the Arrhenius equation do you take ln (1/T1 - 1/T2)
July 21, 2015

Chemistry
We like for you not to use multiple screen names. Use the Arrhenius equation. Use k1 = k1 or choose any convenient number (like 1). Then k2 = 2k1 or twice the number you choose (use 2 if you used k1 = 1) Remember to use K for temperature.
July 21, 2015

Chem
Almost but not quite. You changed by ln 100/33 to ln 0.1/0.33 and that's the error. You divided by 100 so ln 100/33 or ln 1.00/0.33 would be right. Again, that ln 0.100/0.33 gives you a negative number and that gives a negative time which obviously can't be right. ln(1...
July 21, 2015

Chem
Still no. You still did not calculate k. k = 0.693/t1/2 t1/2 from the problem is 24 seconds. k = 0.693/24 = ? Then substitute k into the ln(No/N) = kt formula and solve for t in seconds.
July 21, 2015

also---Chem
Also you know that a negative time makes no sense.
July 21, 2015

Chem
No. You never calculated k.
July 21, 2015

Chem
k = 0.693/t1/2 Substitute k into the below equation. ln(No/N) = kt No = 100% N = 33% k from above Solve for t = time in seconds.
July 21, 2015

Hindu Vidyapeeth
mols HNO3 = grams/molar mass = ? M HNO3 = mols HNO3/L solution = ? Approximately 2 M but that's an estimate.
July 21, 2015

Chemistry
I don't think there is a clear answer. First, a colorimetric measurement is difficult to do on a SOLID sample (reflectance perhaps) so we might be persuaded to choose gravimetric analysis. On the other hand, if there isn't enough sample to weigh accurately (say 1E-15 g...
July 21, 2015

chemistry
delta T = i*Kf*m i is the van't Hoff factor which is 4 for Na3PO4, 2 for NaCl, 3 for MgCl2(you made a typo here), 1 for C6H12O6 and 1 for CH3COOH. Example for Na3PO4. delta T = 4*1.86*0.1 = ? For NaCl: delta T = 2*1.86*0.35 = ? Then freezing point = 0 - delta T = ? So ...
July 20, 2015

Chemistry
mols NiCl2 = M x L = ? mols NaOH = 2 x mols NiCl2. M NaOH = mols NaOH/L NaOH. You know mols and M NaOH, solve for L and convert to mL.
July 20, 2015

GT
A. Expansion work (or PV work) is work = -p(v final-v initial) If p is zero, the PV work must be zero since any number x zero is zero. B. Substitute the numbers into -p(v final - v initial). p is 1.5 for B and 2.8 for C. Delta V is 89.3 - 26.7 = ? mL and change that to L. Work...
July 20, 2015

chemistry
p of gas C = nRT/V. Substitute and solve for pressure of gas C. Then Ptotal = pA + pB + pC = about 1.35 atm.
July 20, 2015

Science
When I read the question it says "the following processes" but then (a) is a statement and not a process. We know PV = k
July 20, 2015

Science
Part of this question appears to be missing.
July 20, 2015

Chemistry
H2SO4 + 2KOH ==> K2SO4 + 2H2O mols KOH = M x L = ? Using the coefficients in the balanced equation, convert mols KOH to mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4.
July 20, 2015

Chemistry
It takes 540 calories to change 1 g H2O from liquid to steam at 100 C. 540 cal/g x #g = 5400 cal. Solve for #g
July 20, 2015

chemistry
heat lost by warm water + heat gained by cold water = 0 [mass warm water x specific heat H2O x (Tfinal-Tintial)] + [mass cool water x speicif heat H2O x (Tfinal-Tinitial)] \ 0 Substitute and solve for Tfinal.
July 20, 2015

org chem
We can't draw diagrams on this forum; I suggest you Google these four substances and you can get pictures/structural formulas there. If you have access to a model kit you can makes these out of ball and stick pieces and sometimes that helps you see the three dimensional ...
July 20, 2015

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