Saturday
July 23, 2016

Posts by DrBob222

Total # Posts: 52,747

chemistry help
mols Na2S2O3.5H2O = grams/molar mass = ? Then M = mols/L.
January 17, 2016

chemistry
mols KMnO4 = grams KMnO4/molar mass KMnO4. M KMnO4 = mols/L Here is the redox part of the reaction and I've balanced that part. You can finish it but the redox part is all that matters. 5Fe^2+ + MnO4^- --> 5Fe^3+ + Mn^2+ mols KMnO4 used = M x L = ? Using the ...
January 17, 2016

chemistry
What do you mean by "characterize"? It is a double salt, it has both ionic and covalent bonds, etc.
January 17, 2016

help fast i need help with a bunsh
Yes, 5/15 = 1/3
January 15, 2016

Chemistry
Would you believe LiCN Li-CN is ionic. C---N is covalent.
January 15, 2016

Chemistry
This is a Limiting Reagent (LR) problem. You know that because amounts are given for BOTH reactants. 1. Write and balance the equation. 2. Convert HBr to mols. mols = grams/molar mass = ? 3. Convert NaOH to mols. mols = grams/molar mass = ? 4. Using the coefficients in the ...
January 15, 2016

Chemistry 101
I would convert feet to cm and mm to cm, then volume = L x W x H = ? density = g/volume in cc.
January 15, 2016

Chemistry
test post?
January 15, 2016

chemistry
Here is a curve for binding energy. Those at the top of the curve have the largest B.E. https://www.google.com/search?q=binding+energy+curve&tbm=isch&imgil=3jjg_qtRsd4lSM%253A%253B8zoG9NlsrjSDlM%253Bhttp%25253A%25252F%25252Fhyperphysics.phy-astr.gsu.edu%25252Fhbase%...
January 15, 2016

Chemistry
mols HNO3 = M x L = ? mols LiOH = M x L = ? mols LiOH - mols HNO3 = mols LiOH in excess. Then (OH^-) = mols excess OH/total volume in L.
January 15, 2016

chemistry
This is about 3 chapters of work. How much do you know how to do on your own? Explain what you do and don't understand.
January 14, 2016

Chemistry
Take a 100 g sample which gives you 69.9 g Fe 30.1 g O mols Fe = grams/atomic mass = ? mols O = grams/atomic mass = ? Now determine the ratio of one element to the other with the smallest being no less than 1.00. The easy way to do that is to divide both numbers by the ...
January 14, 2016

Chemistry
The answer by John suggests that it is the result of each atom having such a small mass (they do) but I assume your question is why are the masses not whole numbers. That's because the value in the periodic table are the averages of all of the different isotopes of the ...
January 14, 2016

Chemistry
CH4 + 2O2 ==> CO2 + H2O dHrxn = (n*dHformation products) - (dHformation reactants) = ? = q for 1 mol CH4. volume of house = 3000cm*3000cm*300cn = ? cc. mols air = ?cc/22,400 = ? How many Joules (or kJ) do you need to heat the house. That's q needed = mols air x specific...
January 14, 2016

chemistry
Use the Henderson-Hasselbalch equation.
January 14, 2016

Chemistry
See my response @ Jan 13 @ 5:25 P.M.
January 13, 2016

Science help....
What air and where in the balloon.
January 13, 2016

Chemistry
Most books now show Fe3O4 as FeO*Fe2O3 (a mixture of Fe(II) and Fe(III) but that shouldn't change any of the calculations. I would have reported 8.54 kg also.
January 13, 2016

Chemistry
It should. 11.8 kg x (3*55.847/231.539) = ? Did you use 0.7236 for the factor (72.36%)?
January 13, 2016

CHEMISTRY
mols C = grams/atomic mass = ? mols H = grams/atomic mass = ? Now find the ratio of the two elements to each other with the smaller number being no less than 1.00. The easy way to do is to divide BOTH numbers by the same small number,then multiply both numbers by any number to...
January 13, 2016

Chem - pH curve
Here is a link with MANY titration curves. Scroll down to the Na2CO3 plus HCl curve and that will be the one you want. http://www.chemguide.co.uk/physical/acidbaseeqia/phcurves.html
January 13, 2016

Chemistry
Ba(NO3)2 + Na2SO4 ==> BaSO4 + 2NaNO3 a. Gravimetric analysis depends upon almost none of the solid dissolving; adding and excess of Na2SO4 is adding a common ion (sulfate ion) which decreases the solubility of the BaSO4. b. mols BaSO4 = grams/molar mass BaSO4 = ? mols Ba(...
January 13, 2016

chemistry
Notice that as you proceed from low to high atomic numbers, the number of neutrons in the nucleus increases faster than the number of protons. Therefore, the high atomic number elements have too many neutrons so the probability is higher to get rid of neutron by converting ...
January 13, 2016

Chemistry Chemical Reactions pls help <3
This is a limiting reagent (LR) problem. mols AgNO3 = grams/molar mass = ? mols CaCl2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols AgNO3 to mols AgCl. Do the same to convert mols CaCl2 to mols AgCl. It is likely the two values for mols ...
January 13, 2016

Chemistry
CH4 + 2O2 ==> CO2 + 2H2O mols CH4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CH4 to mols O2. Then g O2 = mols O2 x molar mass O2 = ?
January 13, 2016

Chemistry
I never heard of a mutualism bond.
January 13, 2016

stoichiometry
For every 100 mol NH3 used 100 mols NO formed at 100% yield. At 70% yield it will form only 70 mols NO. Then 100 molos NH3 initially - 70 mols used = 30 moles left over to be recycled.
January 13, 2016

Chemistry
I think all look ok except I would think Hg is a metallic bond since Hg is a metal. The others look ok. In my book almost nothing is PURE ionic or PURE covalent.
January 13, 2016

chemistry
You must be kidding? 1. Secure tank. 2. Fill tank with water. 3. Unscrew the lid on the jar of Na2CO3. 4. Remove some Na2CO3 5. Sprinkle in tank etc etc. I'm sure you didn't want this but that's what the question asks.
January 13, 2016

Science
50 g sample of ice. -30 C initial T 0 C final T q = mass ice x specific heat solid ice x (Tfinal-Tinitial) = ? To melt the ice at zero to water at zero. q = mass ice x heat fusion ice = ?
January 13, 2016

Chemistry
There are 6.02E23 molecules in 18 g H2O (1 mol). 36 grams is 2 mols.
January 13, 2016

chemistry
Balance the equation. Then use the coefficients in the balanced equation to convert mols NaHCO3 to mols CO2. Finally, convert mols CO2 to grams by g = mols x molar mass.
January 12, 2016

chemistry
Josh, did you proof your problem? You can calculate the original (acid) and (base) this way. pH = pKa2 + log base/acid 7.2 = 7.2 + log base/acid 0 = log b/a 1 = b/a is equation 1 equation 2 is a + b = 0.05 Solve those two equations simultaneously and A = B = 0.025M The buffer ...
January 12, 2016

Chemistry
If you start with neutral S and make a sulfide ion (S^2-) out of it, do you add or lose electrons?
January 12, 2016

chemistry
If the copper sulfate is in solution, this is it. Zn(s) + CuSO4(aq) ==> ZnSO4(aq) + Cu(s) The Zn displaces the Cu^2+ ion.
January 12, 2016

chemistry
H2 + Cl2 ==> 2HCl Since these are gases one may use L (volume) as if the volume were mols. 0.5 L HCl x (1 mol H2/2 mols HCl) = 0.5 x 1/2 = ?
January 12, 2016

Chemistry
2KNO3 ==> 2KNO2 + O2
January 12, 2016

chemistry
First there is no such thing as calcium(iii) oxycarbonate. Ditto for calcium(iv) oxide. CaCO3 + 2HCl ==> H2O + CO2 + CaCl2 mols CaCO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaO. Convert mols CaO to grams CaO by ...
January 12, 2016

Chemistry
Look up the atomic mass of Al and weight exactly that amount of Al on an analytical balance.
January 11, 2016

chemistry
Ivan, Anthony, Juan, we prefer you not change screen names. We can help you better if you keep the same name when you post. %Na = (atomic mass Na/molar mass NaHCO3)&100 = ?
January 11, 2016

chemistry
Technically, I don't think it can be done because I think the problem is misstated. You don't mix solids with 1 L H2O; when making molar solution you use mols and add enough WATER TO MAKE A TOTAL VOLUME OF 1 L. But the think the intent of the problem is to answer as ...
January 11, 2016

Chemistry
a.) How many grams of Hydrogen will be contained in a 100.000 g sample of magnesium hydroxide.? mols MgIOH)2 = grams/molar mass = ? Then mols H ATOMS (not molecules) will be twice that since there are two H atoms per mol Mg(OH)2. Then grams H ATOMS will be g = mols x atomic ...
January 11, 2016

Chem
Would you believe 44.009 grams/mol or the molar mass is 44.009.
January 11, 2016

Chemistry
The percent composition in these problems means to calculate the percent of each element versus the entire compound. It works this way. Suppose you have 10 lbs apples and 5 pounds oranges. What is %apples and %os. %apples = (weight apples/total weight)*100 = (10/15)*100 = 66....
January 11, 2016

Chemistry
Yes. When a reaction gives off heat it is said to be exothermic and the enthalpy of the reaction is negative.
January 11, 2016

Chemistry
The reaction of Mg with oxygen of the air produces heat. It takes more energy to produce white light than red light.
January 11, 2016

@ Damon--math/ chemistry
Already on it. :-)
January 11, 2016

math/ chemistry
Solubility MgF2 = 1.72E-3 g/100 mL. The molar mass is closer to 62.3 than to 62. mols = g/molar mass = 1.72E-3/62.3 = 2.76E-5 mols amd that is in 100 mL; therefore, M = 2.76E-5 mols/0.1L = 2.76E-4. .......MgF2 ==> Mg^2+ + 2F^- I......solid....0........0 C......solid....x...
January 11, 2016

chemistry
It isn't clear what you want? I assume that is you want the specific heat of the metal. Here is your work. = (20g)(c)(x-165)+(125(8.8-5(4.18) Just a change or two. 1. Make that = 0. 2. x is 8.8. If the final T is 8.8, that is not only the final T for the water but also the...
January 11, 2016

Chemistry
The easy way to do this is to solve the Rydberg equation using n1 = 1 and n2 = 7 and a second time for n1 = 6 and n2 = 7. That gives you the range from the shortest wavelength to the longest wavelength, then compare these with the electromagnetic chart to see what range of the...
January 11, 2016

Chemistry
My response above gave only the flame test possibilities. If you mean by "emission spectrum test" the use of a spectroscope or spectrograph instrument, then there are no problems. One can detect and identify as many as about 60 elements with such an instrument and ...
January 10, 2016

Chemistry
Sometimes yes, sometimes no. It all depends upon which elements are to be identified. For example, a mixture of Na and K. The Na yellow flames is so bright that it masks the lavender/purple of the K; however, if you see the Na test, a blue cobalt glass (just a square of glass ...
January 10, 2016

Chemistry
Because some other element may have a line at the same wavelength. So we use TWO lines minimum since an interfering element USUALLY doesn't have a second interfering line. In saying this however, bear in mind that element A may be interfered with at the primary line with ...
January 10, 2016

Chemistry-Dr.Bob
What you say may be right but I believe a better answer is that chemical rxns carried out in an open container do so at constant pressure. The enthalpy, qp is delta H. Energy carried out at constant volume, (in a bomb), qv measured delta E.
January 10, 2016

Chemestry
huh? What about proofing your questions before posting.
January 10, 2016

chemistry
I noticed you used different screen names of Gerry and Bob. It helps us help you better if you stick with the same name.
January 10, 2016

chemistry
Yes, mols = grams/molar mass. By the way, it doesn't matter whether the gas is at STP or any other pressure/temperature combinations, the fact is that 3.59 g is so many moles regardless of the pressure/temperature.
January 10, 2016

Chemistry
Yes, as long as the pressure/temperature of the CH4 is the same as the CO2 being produced.
January 10, 2016

chemistry
units = grams/formula mass mols = grams/molar mass molecules in what? 1 mol of anything contains 6.02E23 of that material.
January 10, 2016

chemistry
mols NO = grams/molar mass 1 mol contains 6.02E23 molecules. So calculate molecules in that many moles.
January 10, 2016

chemistry
See you NO problem.
January 10, 2016

chemistry
See you NO and NH3 problem above.
January 10, 2016

chemistry
How many mols Ar do you have? Since 1 mole contains 6.02E23 atoms, then 6.2E24 atoms of Ar will be 6.2E24/6.02E23 = # moles of Ar atoms. Then since 1 mol Ar weighs 39.9 g, the your # mols will weigh what?
January 10, 2016

stoichiometry
1. You need to find the arrow key(s) and use them. --> is the way to do it. 2. It is better to give a problem with numbers because it makes it easier to explain. In this case mols Fe will be twice the mols Fe2O3. That's what the coefficients in the balanced equation ...
January 10, 2016

Chemistry
No but why can't you do this? You NEVER have to write an equation and ask if it's balanced. You count the atoms and see. I cuont 2C on th left and 2 on the right. I count 4 H on the left and 3 on the right so it isn't balanced. This isn't part of the question ...
January 10, 2016

To Divao ----chemistry
You need to learn where the caps key is and use it. m stands for molality; M stands for molarity. Which do you mean?
January 10, 2016

Chemistry
Your question is about as clear as mud. You should learn how to ask a question. I assume, put into plain English, you have 7E-5 mols CaCl2 and 7E-5 mols Na2SO4, how much BaSO4 is produced. The answer is none. You can't produce BaSO4 unless barium ion is reacted with a ...
January 9, 2016

Chemistry
See my response above to a later post.
January 9, 2016

Chemistry
If the half life was 13 minutes, then 26 minutes is two half lives so you will have just 1/4 (1/2 x 1/2) o 12.5 grams. Here is the way all of these are done. k = 0.693/t1/2 = 0.693/13 = 0.0533 Then ln(No/N) = kt ln(50/N) = 0.0533(26) ln(50/N) = 1.386 50/N = 4 N = 50/4 = 12.5
January 9, 2016

chemistry
The usual case is for the boiling points to be different. I looked up the ortho, meta, and para isomers of toluic acid (methyl benzoic acid). p is 274 C o is 260 C m is 263 C
January 9, 2016

Chemistry
pKa = 3.74 Use the Henderson-Hasselbalch equation. pH = pKa + log base/acid 4.00 = 3.74 + log (HCOONa)/0.1 Solve for (HCOONa).
January 9, 2016

Chemistry
You may work this problem using the Henderson-Hasselbalch equation. Technically that uss concentration of base and acid but you may also use mols and the answer comes out the same. I use mols although concentration is supposed to be substituted. millimols HAc = mL x M = 50 x 0...
January 9, 2016

Chemistry
2C4H10 + 13O2 ==> 8CO2 + 10H2O How much CO2 will you get from 3 mols C4H10. That's 3 x (8/2) = 12. How much CO2 will you get from 12 mols O2? That's 12 x (8/13) - 7.4 The answers are different so you will have some C4H10 left over. All of the O2 will be used.
January 9, 2016

Chemistry
dG = -RTlnK
January 9, 2016

science
I think your question needs clarification. Do you want to know the age of the dog in dog years or do you want to know the age of the dog in human years?
January 8, 2016

Chemistry
Bob P set up the chemistry part. What you are having trouble with is the math. No, you don't put zero for q. You don't need to solve for q. The heat lost by one material + the heat gained by the other material must = to zero and that's the way Bob P set up the ...
January 8, 2016

Chemistry
Jennifer, Bob P set it up for you. All you need to do is to solve for Tf (and look up specific heats).
January 8, 2016

chemistry
Pick a number. Any number you choose will be correct because you didn't specify how much (NH3)3PO4 you have. I assume you means for 1 molecule. There are 3N, 9H, 1P and 4O for a total of 17 per molecule.
January 8, 2016

Chemistry
A limiting reagent problem. 2AgNO3 + Cu ==> Cu(NO3)2 + 2Ag mols Cu = grams/atomic mass = ? mols AgNO3 = grams/molar mass = ? Using the coefficients in the balanced equation: Convert mols Cu to mols Ag Convert mols AgNO3 to mols Ag The smaller number wins; i.e., if AgNO3 is ...
January 8, 2016

Chemistry-Dr.Bob, I need you!!!!
I don't agree with either answer. q from H2O = 200*4.184(5.98) = ? q from calorimeter = 100*5.98 Total q for 0.1 mols is the sum of the two above. Then q/mol = sum/0.1 = ? I get about 55 kJ/mol
January 8, 2016

chemistry
Pb(NO3)2 + 2HCl ==> PbCl2 + 2HNO3 Assuming you meant 0.1M and not 0.1m, millimols Pb(NO3)2 = mL x M = ? millimols HCl = mL x M = ? Determine the limiting reagent and you should see that to be HCl so that means you heave 10 millimols Pb(NO3)2 excess. Convert to mols, then ...
January 8, 2016

Chemistry
What do you mean by "results are attached"? Are those the answers in the key or your answers. Check you typo. H2SO3- should be HSO3^-. ..........NaHSO3 ==> Na^+ + HSO3^- I..........0.05.......0......0 C........-0.05.......0.05....0.05 E..........0.........0.05.......
January 7, 2016

CHM 105
mols CH3COOH = mols NaOH = M x L = ? grams CH3COOH = mols CH3COOH x molar mass CH3COOH % w/w = (mass CH3COOH/mass sample)*100 = ?
January 6, 2016

Chemistry
BeCl2 is a polar compound and is soluble in water. There is no such compound as H-C=C-H. If you mean ethylene (H2-C=C-H2) it is hardly soluble. If you mean acetylene (HCtripleCH) it is slightly soluble but neither are polar.
January 6, 2016

Chemistry
If you have trouble with a problem like this with "reasoning it out", I suggest you assign numbers. Perhaps something like this. Say A = 100 g and is twice B which makes B 50 g. Check that. Specific heat A = 1. B is 2x A so B is 2. Check that. Initial T A = 100; ...
January 6, 2016

Chemistry
You would have done better to post the problem. It's harder to explain in words and not numbers. mols MgCl2 = grams MgCl2/molar mass MgCl2. Then there is 1 mol Mg atoms in 1 mol MgCl2. That is, the number of mols Mg atoms will be the same as the mols MgCl2.
January 6, 2016

Chemistry
CCl4 is the highEST boiling point which means CCl4 should be at the top. CH4 has the lowest b.p. so it should be at the bottom. CH4.....(CHCl3/CH3Cl).....CCl4. So place CHCl3 and CH3Cl in the proper order to make it increasing b.p. from CH4 to CCl4.
January 6, 2016

Chemistry
Try this. The higher boiling point often is the compound with the higher molar mass.
January 6, 2016

Chemistry
There are 6.02E23 atoms in 1 mol. mols Cl2 = 1.2E24/6.02E23 = ? grams = mols x molar mass = ?
January 6, 2016

Chemistry:normal notation plz help
Is that the last electron, the single electron, the outside electron. I assume it's the single electron. Go through each one this way. 19K = 1s2 2s2 2p6 3s2 3p6 4s1 For the 4s1 electron, n = 4 so it can't be K. Also note that s electrons have l = 0; another reason it ...
January 6, 2016

Chemistry
Cu(OH)2 ==> Cu^2+ + 2OH^- i. Adding HCl. The H^+ reacts with the OH^- to produce H2O (H^+ + OH^- => H2O), the OH^- is reduced and that shifts the equilibrium to the right (to increase the OH) which means the solubility is increased. ii. Cu(NO3)2 ==> Cu^2+ + 2NO3^2- ...
January 3, 2016

Chemistry
1. First, balance the Fe/MnO4 equation but correct it first. The part that matters is 5Fe^2+ + MnO4^- ==> 5Fe^3+ + Mn^2+. a. Millimols MnO4 used = M x mL = 12.08 x 0.200 = approx 2.4. Using the coefficients in the balanced equation, convert mmols MnO4 to mmols Fe. That'...
January 3, 2016

chemistry
You need to explain what the direct and indirect methods are.
January 3, 2016

chemistry
Adding a common ion to an insoluble salt decreases the solubility of the salt. Cl from the HCl is the common ion (to Cl in AgCl).
January 3, 2016

chemistry
lead nitrate is soluble. The white ppt formed with NH3 is Pb(OH)2. NH3 + H2O ==> NH4^+ + OH^- Pb^2+ + 2OH^- ==> Pb(OH)2
January 3, 2016

Chemistry
Of course there are but doesn't it all depend upon what you want it to do? For example, it is very good at measuring the masses of groups of atoms but not very good at measuring the boiling point or freezing point of a material.
December 29, 2015

chemistry
How much of the stock solution do you need to prepare? Then mols you need = M x L = ? Then mol = grams/molar mass. You know molar mass of the material and mols, solve for grams.
December 29, 2015

Chemistry
I assume methyl benzene will dissolve sulfur. Dissolve, filter and the iron filings stay in the filter paper. Let the filtrate sit and the solvent evaporates leaving the S behind.
December 29, 2015

chemistry
Your question isn't clear to me. The amount of water necessary to dissolve 10g of the compound is 100 x (10/6.8) = ? but that isn't what is needed to crystallize.
December 29, 2015

chemistry
How much do you need to prepare? mols needed = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
December 29, 2015

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