Wednesday
February 10, 2016

Posts by DrBob222

Total # Posts: 51,344

Chemistry
I don't know enough about how you separated this mixture to answer. I may be able to help if you type in the entire procedure.
September 23, 2015

chemistry
Is that 15.6% w/w or w/v? I will assume w/v. 15.6 % (w/v) means 15.6 g protein/100 mL. So in 240 mL you will have 15.6 g protein x (240/100) = ? g protein.
September 23, 2015

chemistry
See your post above.
September 23, 2015

chemistry
See your other posts.
September 23, 2015

Chemistry
If it did not react with the water, standing would allow much of the volatile substance to escape. You could heat the water to remove move of it since gases are less soluble in hot water than cold water.
September 23, 2015

college chemistry
I responded to this in detail at your first post. You need to go back and check for answers before posting again.
September 23, 2015

Chemistry
Decrease by 68.2% means amount remaining is 100-68.2 = ? = At 1/(A)t - 1/(A)o = kt
September 23, 2015

Chemisty
I don't go along with the "to completely neutralize this sample" since this is a redo reaction and not an acid/base reaction. But I know what you mean. mols KMnO4 = M x L = ? mols H2O2 = mols KMnO4 x (5/2) = ? That = mols in the 25 mL H2O2 and that times 40 = ...
September 23, 2015

chemistry
You should get a second opinion but I believe the answer is skim milk. However, I'm not an organic chemist.
September 23, 2015

Chemistry
I believe you are confused with the formula. speed of light = frequency x wavelength 3E8 m/s = 6.10E14*wavelength
September 23, 2015

Attention Connections Academy students!!!
I think the message here is good; i.e., give your teacher(s) a chance to help. I would have felt better; however, if the person posting this message had used better grammar and had checked out the facts. We sometimes give answers but most of the time we give tips/hints/or web ...
September 23, 2015

college chemistry
mass P2O5 = mass MgNH4PO4.6H2O x (molar mass P2O5/2*molar mass MgNH4PO4) = ? %P2O5 = (mass P2O5)/mass sample)*100 = ?
September 23, 2015

Chemistry
You started off very good but messed up a few times before the end. 1. You had 400 mL of the solution (200 mL HCl + 200 mL NaOH = 400 mL) and that is 400 grams solution. 2. I note you carry out the molar masses to the nth degree, then use 4.20 for specific heat. This isn't...
September 23, 2015

Chemistry
mass = volume x density or volume = mass/density You know the mass and density, solve for volume, then volume = (length side)^3, Plug in the volume, take the cube root, and you have the length of the side.
September 23, 2015

Chemistry
At = 0.019 x 0.25 = ? (If 75% decomposes it must leave 25%). Ao = 0.019 You know k. Plug into the equation and solve for t. I get 143.5 s and that rounds to 140 s to 2 s.f. (dictated by 0.019)
September 23, 2015

Chemistry 102
delta T = i*Kf*molality i = 2.7 k = 1.86 molality = mols/kg solution. mols = 6.60/molar mass MgCl2 and kg solvent = 0.110 Finally, 0-delta T = new freezing point.
September 23, 2015

Chemistry
% w/w = (mass solute/mass solution). You don't have the mass of the solution nor do you have a way of determining it. For molarity. mols solute = grams solut/molar mass solute. Then M = mols/L solution = mols solute/0.1 L = ?
September 23, 2015

Chemistry
mols sucrose in 1.76E24 molecules = molecules/6.02E23 = ? Then grams = mols x molar mass = ? I didn't check the math on a through c but the method is right.
September 23, 2015

Chemistry
You are absolutely right. Good work.
September 23, 2015

AP Chemistry
I agree with your answers to B, C, D. I'm inclined to choose 3 for A since that has more to do with surface area than 4.
September 23, 2015

Chemistry
Take a 100 g sample which gives you 40.00 g C 6.67 g H 53.33 O Convert to mols. 40.00/atomic mass C = ? 6.67/atomic mass H = ? 53.33/atomic mass O = ? Now find the ratio of thre elements to one another with the smallest number being 1.000. The easy way to do that is to divide ...
September 23, 2015

Chemistry
How many moles of ammonium ions and how many moles of sulfate ions are contaiuned in a 0.400 mile sample of (NH4)2SO4 0.400 mol (NH4)2SO4 x [2 mols NH4^+/1 mol (NH4)2SO4] = ? 0.400 mol (NH4)2SO4 x [1 mol SO4^2-/1 mol (NH4)2SO4] = ? Referring to the 0.400 mole sample of (NH4)...
September 23, 2015

chemistry
Is this before or after the disproportionation. Before: (Fe^3+) =- 0.05 x 3/28 = ? (Fe^2+) = 0.05 x 25/28 = ? or more simply, it is [(0.05 x 3/25)/(0.05 x 25/28)] or just 3/25 = ?
September 23, 2015

chemistry
We don't have any way of knowing what you are working on.
September 23, 2015

chemistry
How many mols do you want? That's M x L = ? Convert mols to grams. grams = mols x molar mass.
September 23, 2015

chemistry
See your other post.
September 23, 2015

chemistry
mols CaO = grams/molar mass = ? mols SO2 = use PV = nRT to determine the initial amount of SO2 and the final amount of SO2, subtract final - initial to find mols SO2 used. Convert mol USED of SO2 to mols CaSO3 formed, then g CaSO3 = mols CaSO3 x molar mass CaSO3. I think the 8...
September 23, 2015

Chemistry
I don't see a chemical reaction so I'll assume one. 2KI + Pb^2+ ==> PbI2 + 2K^+. 8 mols KI x (1 mol PbI2/2 mols KI) = 8 x 1/2 = ?
September 23, 2015

Chemistry
Copper(II) chlorate has the formula of Cu(ClO3)2. mols Cu(ClO3)2 = M x L = ? mols Cu(II) ion = mols Cu(ClO3)2 since there is 1 mol Cu ions in 1 mol Cu(ClO3)2. The problem doesn't ask but how many mols chlorate (ClO3)^- do you have. You will have twice as many as there are ...
September 22, 2015

Chemistry
1) a. Write and balance the equation which you have. b. mols base Ca(OH)2 = grams/molar mass = ? c. Using the coefficients in the balanced equation, convert mols base to mols acid. d. Now convert mols acid to grams = mols acid x molar mass acid.
September 22, 2015

Half-Life
ln(No/N) = kt No = 100 N = 10 k from the problem t = ? solve for this.
September 22, 2015

Gr 12 chemistry
Look at the equation. 1 mol I2 will produce 2 mols HI; therefore, 0.530 mols HI will require 1/2 that of I2.
September 22, 2015

Chemistry
If you mix the solids nothing happens. If you mix the solutions nothing happens.
September 22, 2015

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Specific heat H2O = 1 cal/g*C
September 22, 2015

chemistry
mols B2H6 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols B2H6 to mols NaBH4. Now convert mols NaBH4 to volume with M = mols/L solution. You know M and mols, solve for L solution and convert to mL.
September 21, 2015

chemistry
From the question I assume we know that O2 is the limiting reagent and butane is the excess reagent. mols butane = grams/molar mass = ? mols O2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols O2 to mols butane. That will give you the mols ...
September 21, 2015

Biology/ Chemistry
How many mols do you want? That's M x L = mols = ? How many grams is that? That's g = mols x molar mass = ?
September 21, 2015

Chemistry
I would put this on a piece of graph paper, plot % vs density. You can look at it and tell that it must be just about 70%.
September 21, 2015

Chemistry
How much heat do you get from the 7.47 g C6H6 if you get 3.27E6 J from 1 mol C6H6 (78 grams)? That's 3.27E6 J x (7.47/78) = ? = q Then q = mass H2O x specific heat H2O x (Tfinal-Tinitial) I would convert kg H2O to g and use specific heat as 4.184 J/g*C and solve for Tfinal...
September 21, 2015

Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)
September 21, 2015

oops typo---Chemistry 2
See the ( and I meant *. Using dH and dS calculate dGf for A, B, C, then dGrxn = (n*dGf products) - (n*dGf reactants)
September 21, 2015

Chemistry 2
Using dH and dS calculate dGf for A, B, C, then dGrxn = (n*dGf products) - (n(dGf reactants)
September 21, 2015

Chem
copper(I) iodide cobalt(II) fluoride
September 21, 2015

Chemistry
1. 4.5 years x (1 decade/10 years) = ? decades. 3. 18,165 g x (1 hg/100 g) = ? hg 5. 0.874 g x (100 cg/g)
September 21, 2015

honors chem
You're right, you must use Avogadro's number but I don't understand the question.
September 21, 2015

Chemistry
Write balanced equations for the combustion of ethane and ethene. I have 2C2H6 + 7O2 ==> 4CO2 + 6H2O C2H4 + 3O2 ==> 2CO2 + 2H2O Use PV = nRT and solve for mols of the ethane + mols ethene. Let X = mols ethane and Y = mols ethene Then X + Y = mols from above. This is ...
September 21, 2015

Chemistry
No temperature is listed in the problem but usually this is at room T; therefore, the only gas is O2.
September 21, 2015

Chemistry
You have 454 g camphor. mass %O in camphor is 10.24% so 454 x 0.1024 = ? g O
September 21, 2015

AP Chemistry
HCl + NaOH ==> NaCl + H2O How many mols HCl used for the titration? That's mols HCl = M x L = ? How many mols for NaOH. That must be the same as mols HCl. So you have that many mols NaOH in 75 mL, and (NaOH) = mols/L = ? All of that business about 350 mL, 6M, unknown ...
September 20, 2015

CHEMISTRY
From this step, Using 1 amu = 1.6605E-27 kg I got (0.0010114u)(1.6605e^-27kg) =3.1565365e^-15kg I don't believe this math is correct. Estimate 1E-3*1.7E-27 = about 1.7E-30
September 20, 2015

CHEMISTRY
I didn't look at all of it but 1 amu = 1.6605E-27 kg
September 20, 2015

Chemistry
k = 0.693/t1/2 ln(No/N) = kt No = 100 (but you can start with any number you wish but with any other starting value you must calculate percentage differently. N = ? k from above time = from the problem Solve for N and since you started with 100 that is the percent remaining ...
September 20, 2015

Chemistry
What about them?
September 20, 2015

AP Chemistry
I agree with you from the choices given but I would choose temperature first if given that choice.
September 20, 2015

Chemistry
mols KMnO4 = M x L = ? Using the coefficients in the balanced equation, convert mols KMnO4 to mols Fe(II). Convert mols Fe(II) to grams Fe. g = mols x atomic mass Fe. %Fe = (mass Fe/mass sample)*100 = ?
September 20, 2015

chem
incomplete question.
September 20, 2015

chemistry
Where are you with this one? Convert mass CO2 to mass C. Convert mass H2O to mass H(atoms). 1.0g - mass C - mass H = mass O Convert g C to mols. Convert g H to mols Convert g O to mols. Find the ratio for the empirical formula. Then (emprical formula) x number = molar mass. ...
September 20, 2015

Chemistry
mols Fe2O = grams/molar mass = ? mols Fe = twice that since there are two mols Fe in each mole of Fe2O3. Then %Fe = (mass Fe/mass sample)*100 = ?
September 20, 2015

chemistry
WO3 + 3H2 ==> 3H2O + W mols WO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols WO3 to mols H2O. Now convert mols H2O to grams H2O. This is the theoretical yield (TY). The actual yield (AY) is given in the problem as 9.60 grams (since ...
September 20, 2015

chemistry
https://www.youtube.com/watch?v=zbXqpZHX7wM
September 20, 2015

science
http://www.kemix.com.au/Laboratory-preparation-of-chloroform-from-ethanol
September 20, 2015

science
2,3-dimethyl what?
September 20, 2015

Chemistry help
Follow the template for the UF6 problem.
September 20, 2015

Chemistry problem
2.14 mol CF4 x (4 mol F/1 mol CF4) x (1 mol UF6/6 mol F) = ? mol UF6.
September 20, 2015

Chemistry
1 lb = 453.6 grams. volume = mass/density. Plug in mass and density and solve for volume for each. Subtract the two to find how much more
September 19, 2015

Chemistry Help!
Thank you for letting me know.
September 19, 2015

Chemistry Help!
1. Write and balance the equation. 2. Convert g C2H4O to mols. mols = grams/molar mass. 3. Using the coefficients in the balanced equation, convert mols C2H4O to mols H2O. 4. Now convert mols H2O to grams. g = mols x molar mass.
September 19, 2015

Science
I suggest you give the link from left to right but leave a space somewhere in the link; i.e., if you want to give the link of Jiskha.com write it this way. J iskha. com and I think it will post that way. Then someone here can copy that as the URL, remove the spaces, and get ...
September 19, 2015

chemistry
See the similar problem by han below and use the same format to solve your problem. Post your work if you get stuck.
September 19, 2015

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
September 19, 2015

chem
By the way, you need to learn to use the caps key when needed. You have CO and Cl2 going to cobalt chloride. How many mols do you have at equilibrium? That's PV = nRT. You know R, T, V, and Total P, solve for total n. Then ...........CO + Cl2 ==> COCl2 I..........1.0..1...
September 19, 2015

AP Chemistry
1 H2(g) yIelds 2H(g) Delta H = 436 kJ/mol 2 F2(g) yields 2F(g) DeltaH = 158 kJ/mol 3 H(g) + F(g) yields HF(g) DeltaH = -568 kJ/mol Calculate deltaH for: H2(g) + F2(g) yields 2 HF(g) Bold face I have numbered the equations. Add eqn 1 to eqn 2 and add twice the equation 3. That ...
September 19, 2015

CHEMISTRY !!! HELP !
If you know the answer let me see it and I'll see if I can work around to the answer; otherwise, this last looks ok to me.
September 19, 2015

CHEMISTRY !!! HELP !
So how did you do it? Show your work; probably I can find the error. Did you try this? k1 = (H^+)(HM^-)/(H2M) k2 = (H^+)(M^2-)/(HM^-) so k1*k2 = (H^+)^2(HM^-)(M^2-)/(HM^-)(H2M) Cancel the HM^- in numerator and denominator, substitute the numbers for the others and solve for (H...
September 19, 2015

CHEMISTRY !!! HELP !
I'm sure you know to use the HH equation. So what's the trouble? Not know which k to use. Or something else.
September 19, 2015

chemistry(ch1001)
I don't agree with all of your numbers but most are close, anyway, and I don't think it will make much difference in the empirical formula. I don't know what else you want. Apparently you didn't type in the entire problem since it says nothing about the molar ...
September 19, 2015

chemistry
well, am I every embarrassed to make a simple freshman mistake. You are absolutely right and I am way way wrong. Yes, Keq = (Br^-)^2/(Br2) (0.012)^2/(0.063) = 0.00228 so Qc>K, the rxn will proceed to the left so the equilibrium should be written as ........Br2 ==> 2Br...
September 19, 2015

chemistry
...............Br2 ==> 2Br I............0.063....0.012 First you must determine which way the reaction will proceed; i.e., to the left or to the right. Qc = (Br2)/(Br)^2 = 0.063/(0.012)^2 = about 440 and kc = 0.0011 so Qc is larger which means Br2 is too high and Br is too ...
September 19, 2015

Chemistry
You can go to this site and determine the order. I don't believe second order is correct. https://en.wikipedia.org/wiki/Reaction_rate_constant#Units I would do this as if it were a stoichiometry problem. Calculate the rate for each. For example, for #1 (O2), it is 0.4 x (9...
September 19, 2015

chemistry
We can't draw structures on this forum. You name this with the longest chain. What do you think that is? And don't answer 6.
September 19, 2015

college algebra
Isn't that (9395.59/yr) x (1 yr/52 weeks) = ?
September 18, 2015

chemistry
I recommend that you look at the first graph shown and pick out some height, note the temperature, then compare that with the boiling point or the freeziang point of the material in the question. That will let you decide if it is a solid, liquid, or gas. The question isn't...
September 18, 2015

Chemistry
This is a limiting reagent (LR) problem. mols Mg = 10.2/24.3 = about 0.42 but you need a more accurate answer. mols O2 = 11.8/32 = about 0.37 and 2 mols MgO/1 mol O2 = about 0.42/2 = about 0.21 and you have that much O2. Therefore, Mg must the LR. mols Mg = 0.42 mols MgO ...
September 18, 2015

Chemistry
It's hard to explain in writing but here goes. 19.3 inches x factor = ? cm So your only problem is two fold; i.e., 1. you must know the factor. You show it in this case as 1 inch = 2.54 cm 2. Decide which way to turn the factor; i.e. as (2.54 cm/1 in) or (1 in/2.54 cm). So...
September 18, 2015

Chemistry
John, look at the same question by anon above (several questions above). I think I have solution shown there is you can decide how many of these heights the problem is asking for.
September 18, 2015

Chemistry
I'm not sure how it relates to this question either. After re-reading the question I don't know that it's so straight forward either. Here is a link that talks about atmospheric temperature. https://en.wikipedia.org/wiki/Atmospheric_temperature However, if they don...
September 18, 2015

Chemistry
What is your problem with this question? It seems straight forward to me.
September 18, 2015

Chemistry
That looks ok to me but I would add a % sign after -1.5. Also, since you show that as an absolute value in your formula I would think the answer to be +; however, in chemistry I always keep the - sign. That is, I would remove the absolute sign in the equation. Follow what you...
September 18, 2015

Chemistry
q = 63,000 x 80 = ?
September 18, 2015

organic chem
I don't see a question here.
September 18, 2015

Chemistry
c1v1 = c2v2 0.500*x = 0.125*45 Solve for x = volume of the 0.500 M stuff you have. Pipet that amount into a 45 mL volumetric flask and make to the mark with DI water. Yes, I know 45 mL volumetric flasks are not common. Neither are 11.25 mL pipets.
September 18, 2015

Chemistry
I assume you are asking for the mass of the Cu since you already have the mass of the water. [mass Cu x specific heat Cu x (Tfinal-Tinitial)] + [mass H2O x specific heat H2o x (Tfinal-Tinitial)] = 0 Substitute the numbers and solve for mass Cu metal.
September 17, 2015

Chemistry
http://www.jiskha.com/display.cgi?id=1442317973
September 17, 2015

Organic Chemistry
mols conjugate base = grams/molar mass = ? 1 mol conjugate base aspirin = 1 mol HCl. M HCl = mols HCl/L HCl You know M and you know L HCl, solve for mols and compare mols HCl with mols conjugate base.
September 17, 2015

Chemistry
That looks good to me. Good work.
September 17, 2015

Chemistry
I get 6E-3/2.9E-7 = 2E4
September 16, 2015

Chemistry
mols C2H6O = grams/molar mass = ? mols C atoms is twice that since there are two mols C atoms/mol C2H6O.
September 16, 2015

Chemisrty
6.02E23 atoms P weigh 32.097 grams. So 6.14E21 atoms will weigh .....?
September 16, 2015

Chemistry
mass Hg = volume x density = ? 200.59 g Hg contains 6.02E23 atoms Hg. So ? g Hg will have ...... atoms Hg.
September 16, 2015

Chemistry
Note this doesn't add to 100% but I'll assume it does. I don't think that will change the formula. Take 100 g sample to give you 74.0 g C 8.65 g H 17.3 g N Convert to mols. 74/12 = ? 8.65/1 = ? 17.3/14 = ? Find the ratio of these numbers with the smallest being 1....
September 16, 2015

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