Monday
August 29, 2016

Posts by DrBob222

Total # Posts: 52,871

Chemistry 101
Same answer I gave you yesterday.
January 20, 2016

Chemistry-Dr. Bob
I don't understand how you obtained this value for work. P is 1 atm (STP) and delta V is 1L. Right?
January 20, 2016

Chemistry- Dr.Bob
When I convert 12 psi to atmosphere I don't get your value but something closer to 0.8. Making that change makes the other answers change but the procedure looks ok. I check the calculation for the first one and it is ok (except for P). I didn't check the math for the ...
January 20, 2016

Chemistry 105
If that is 23 g (and not 23.0 or 23.00 etc), then the sum of 23 + 0.022 = 23
January 20, 2016

Chemistry
........HNO2 ==> H^+ + NO2^- I.......0.02.....0......0 C......-6e-4....6e-4...6e-4 E........you fill in.
January 20, 2016

Chemistry
What about it?
January 20, 2016

chemistry
Use the Clausius-Clapeyron equation but you will need the heat of vaporization.
January 20, 2016

Chemistry
It's LeChatelier's Principle. If a reagent is added to a system at equilibrium the reaction will shift so as to undo what we've done to it. So if you add water, it will shift so as to use up the water you've added. Since H2O is on the right the rxn will shift ...
January 20, 2016

Chemistry- Dr.Bob!
Start out with PV = nRT, plug in the numbers and solve for n = number of mols of air. Correct for 20% O2 and go from there. Post your work if you get stuck.
January 20, 2016

Chemistry
I agree with Scott.
January 19, 2016

Chemistry
Why don't you show the math so we will know what is confusing you instead of us guessing at the problem. Here is the chemistry. .........N2 + 3H2 ==> 2NH3 I.......0.1...0.1......0.1 C.......-x....-3x......2x E......0.1-x..0.1-3x...2x Kc = 0.04 = (NH3)^2/(N2)(H2)^3
January 19, 2016

Chemistry
4Al + 3O2 ==> 2Al2O3 mols Al = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Al to mols Al2O3. Finally, convert mols Al2O3 to grams. g = mols x molar mass = ?
January 19, 2016

Chemistry
The English is not too good, all of the information is not included, and you are using too many screen names. Anitta, Angelica, Marley, to name just three.
January 19, 2016

@ Bob Pursley
I think the answer to that is 10 mL.
January 18, 2016

chemistry
mols NaCl = M x L = 0.25 x 0.01 = ? g NaCl in the dish is mols x molar mass = ? and that's the amount in the dish after evaporation of the water.
January 18, 2016

chemistry
You can balance the entire equation if you wish but the only part that matter is the redox part. Here is that part. 5C2O4^2- + 2MnO4^-==>2Mn^2+ + 10CO2 mols KMnO4 = M x L = ? Using the coefficients in the balanced equation, convert mols KMnO4 to molsl Na2C2O4. Then grams ...
January 18, 2016

Chemistry 101
mass crown - 2,650 grams. volume crown = 145 mL density = m/v = 2,650/145 = 18.3 g/mL. It isn't pure Au.
January 18, 2016

Physical sciences
You need to learn to do these yourself. potassium bromide sodium carbonate iron(II) sulfate chromium(III) chloride.
January 18, 2016

chemistry 110
2HNO3 + Sr(OH)2 ==> Sr(NO3)2 + 2H2O mols Sr(OH)2 = M x L = ? Using the coefficients in the balanced equation, convert mols Sr(OH)2 to mols HNO3. Then M HNO3 = mols/L. You know mols and M HNO3, solve for L (and convert to mL if needed).
January 18, 2016

chemistry
I don't think the problem is made up to be a REAL problem. SCxOy is the compound. 8.99 g Sc used. 8.99-3.56 = 5.43 g O used. Total mass ScxOy = 8.99+5.43 = 14.42 %O = (5.43/14.42)*100 = ? but in REAL Sc2O3 the %O is 34.8%.
January 18, 2016

chemistry
You don't have any units for the coefficients so I don't know where you are but the formula to use is (dL/L)= k*dT So plug in dL and L in the proper units and the 25 and solve for dT. Knowing it is 20 at the end calculate the initial T.
January 18, 2016

Chemistry
Large Kb means large OH so pH will be high.
January 17, 2016

chemistry help plz
mols KMnO4 = grams/molar mass M = mols/L. 5Fe^2+ + MnO4^- ==> 5Fe^3+ + Mn^2+ mols KMnO4 used = M x L. You don't show L KMnO4. Without that you can't finish the problem.
January 17, 2016

chem
Zn + 2HCl ==> H2 + ZnCl2 mols HCl used = M x L = ? Using the coefficients in the balanced equation, convert mols HCl to mols Zn. Then mols Zn = grams Zn/atomic mass Zn. You know atomic mass and mols Zn, solve for grams Zn.
January 17, 2016

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

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