# Posts by DrBob222

Total # Posts: 54,773

Organic chemistry
The melting point of a mixture is lower than the melting point of either pure compound.

analytical chemistry
I assume you mean ppmw (ppm by mass and not by volume) So mass H2O in that 1 L is 1000 g and that added to the 0.361 gives you a mass of solution of 1000.361g. 0.361g x (1E6/1000.361) = ? ppmw and you round that off to three significant figures and you get the same answer as ...

Chemistry
http://chemicals.etacude.com/c/more/cuso4.html

Chem
(V1/T1) = (V2/T2)

Chem
Actually HF is approximately 50% ionic/50% co-valent character. In fact, Linus Pauling, when he developed his electronegativity scale (F = 4.0 arbitrarily), I understand that he used 50% for HF

Math for Ms. Sue
I believe any number one chooses (over two) will be the correct number of pizzas to buy; the problem doesn't say there can't be any pieces left over. So anything over 2 pizzas will, in my opinion be right. 2 pizzas will give 16 slices and 16/14 = 1+. So each student ...

@ Reiny & Steve--Math - check answer
As well as for the tutors. :-)

chemistry
30 x (atomic mass Fe/molar mass FeSO4) = ?

College Chemistry
mols MgCl2 = grams/molar mass = ? M MgCl2 = mols MgCl2/L = ? Technically, there isn't any MgCl2 since all of it is ionized completely; however, I think the spirit of the question is to give the concentration of the salt, MgCl2. You will have 2.39E-4 g Mg ^2+ there and that...

chem
Your best bet is to get a 250 mL beaker that is marked every 25 mL and look to see about how close you think you can come to estimating the volume. I'm not looking at one, but I might guess at 5 mL but that is strictly a guess.

Chemistry AP
Is that Kc or Kp? I will assume it is Kp since the pressures are given but the problem is worked the same way for each (Kp is used with partial pressures; Kc with concentrations in mols/L) K = 1.9 Q = p(PCl5)/p(PCl3)*p(Cl2) Q = (0.5)/(0.5)(0.5) = 2 Looking at Q = 2, that is &...

Chemistry
http://www.jiskha.com/display.cgi?id=1474173035

Chemistry
.......Ca(OH)2 ==> Ca^2+ + 2OH^- I......solid.......0........0 C......solid........x.......2x E......solid.......x........2x Ksp = (Ca^2+)(OH^-)^2 Substitute the E line into the Ksp expression and solve for x. That will give you the solubility of Ca(OH)2 in mols/L. That is ...

Chemistry
mols NaOH in 5.52 grams is mols = grams/molar mass = ? mols NaOH in the solution of NaOH is mols = M x L = ? Total mols NaOH = mols in the 5.52g + mols in the solution = ? Convert 1.52 gallons to L. 1 gallon = 3.785 L. total volume is L in 1.52 gallons + 659 mL(convert to L ...

Biochem
I think you need the total concentration of the buffer; i.e., you want 20 mL of what? 0.05M, 0.01M, what M. Here is a problem just like that which I worked earlier last week. http://www.jiskha.com/display.cgi?id=1470250931

Chemistry
That looks good to me.

Chemistry
The mass of an empty container is 91 g. The mass of the container filled with water is 111 g. What is the volume of the container? The density of water is 1 g/cm3 .Answer in units of cm3 20cm3 right 016 (part 2 of 5) 1.0 points The container was emptied, dried, and a piece of ...

Chemistry
The polarity of H2O causes the H2O molecules to "stick" (more or less) to each other. It also has adhesive properties and you can see that if you suck water up into a glass tube. The tube needs to be about 1/2 inch in diameter. You will see the edges of the water ...

chem
I would convert to g first.

science chemistry
CuS + 6H^+ + 3SO4²- = CuO + 4SO2 + 3H2O

chemistry
mass # = #p + #n 16 = #p + 7 p = 9 So it must have 9 electrons so the charge must be -1 when the anion is formed. 9F^16. 9 is the subscript; 16 is the superscript and goes at the top left.

chemistry
What you did, and you needed to that, is convert 1.4E2 pm to cm. Then (1.4E-5 cm/atom) x # atoms = 1 cm. Solve for # atoms in the 1 cm.

chemistry
q1 = heat needed to melt ice at 0C q1 = mass ice x heat fusion = ?J q2 = heat needed to raise T of liquid H2O from 0C to 85 C q2 = mass H2O x specific heat H2O x (Tfinal-Tinitial) = ? J Total q = q1 + q2 = ? in J. Convert to kJ.

PbI2 ==> Pb^2+ + 2I^- If you have a saturated solution of PbI2 then Qsp = Ksp = (Pb^2+)(I^-)^2 Adding KI ==> K^+ + I^- So you are increasing the (I^-), that is adding the common ion I^- to the saturated solution so the reaction shifts to the left forming more PbI2. OR, ...

Please explain how you eliminated answer C. The rule with gases is that an INCREASE in P makes the reaction shift to the side with FEWER mols which means an increase in P and the reaction shifts to the right in this reaction (2 mols on right; 3 mols on left). It follows that a...

CHEMISTRY
Generally that is NaOCl.

Chemistry
initial (N2) = 1/10 = 0.1 initial (H2) = 1/10 = 0.1 equilibrium (H2) = 0.4/10 = 0.04 .......N2 + 3H2 ==> 2NH3 I.....0.1..0.1......0 C.....-x....-3x.....+2x E..0.1-x...0.1-3x...2x The problem tells that 0.1-3x = 0.04 so x = 0.02. That allows you to calculate composition of ...

oops. here is Kp--Chemistry
Find Kp by Kp = Kc(RT)^delta n. Remember S is a solid and not a gas.

Chemistry
......H2S ==> H2 + S(s) I.....0.7.....0.....0 C.....-x......x.....- E...0.7-x.....x.....- NOTE that S is a solid and isn't in the Kc expression: Kc = (H2)/(H2S) Substitute the E line into Kc expression and solve for x = (H2) in mols/L. The problem asks for grams S and ...

Chemistry
Use PV = nRT and solve for p= pressure at the initial conditions listed. You can go through the math but I've estimated initial p = 0.05 atm. Of course you need a more accurate number than that. ......NOBr ==> NO + 1/2 Br2 I....0.05......0........0 C.....-p.......p...

Camestry
mass = volume x density. Substitute and solve.

Chemistry
There's the long way, a shorter way, and a short cut that isn't taught in schools anymore. Long way. mols CaCl2.6H2O = grams/molar mass = ? mols CaCl2 = mols CaCl2.6H2O since there is 1 mol CaCl2 in 1 mol CaCl2.6H2O Finally, g CaCl2 = mols CaCl2 x molar mass CaCl2. ...

Chemistry
CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 mols HCl = M HCl x L HCl = ? Using the coefficients in the balanced equation, convert mols HCl to mols CaCO3. That will be mols HCl x (1 mol CaCO3/2 mols HCl) = mols HCl x 1/2 = ? Then convert mols CaCO3 to grams. g CaCO3 = mols CaCO3 x ...

Chemistry
I don't understand the questions since some have units and others don't. For first one, I have 2.865E4 x 1.47E3 = 4.21155E7. The first number has 4 s.f. and second has 3 s.f. The rule in multiplying is that the final answer may have no more s.f. than any of the numbers...

Chemistry
Is that concn in M (mols/L). I will assume so. mols NaCl = 73.28/58.44 = ? mols Cl = same as mols NaCl Then M Cl = (mols/0.862L) = ?

Chemistry
I don't think so. 1E5 mL = 1E5 cc = 1E5 cm^3. There are 100 cm in a m; therefore, 1E5 cm^3 x (1 m/100 cm)^3 = ? m^3 which I think is 0.1 m^3.

Chemistry
mols CuCl2 = g/molar mass = 0.00628/molar mass CuCl2 = ? Then there are two Cl^- for every mols CuCl2.

AP CHEM
Separate the molecular equation into ions using the following rules. 1. If the substance is soluble, show the ions with (aq) after + and - ions. 2. If a gas so that as a molecule and write (g) after it. 3. If a solid, show it as the molecule and write (s) after it. 4. If a ...

Chemistry
As far as I can tell, dolomite is a 50/50 mixture (mostly) of CaCO3 and MgCO3. CaCO3 ==> CaO + CO2 MgCO3 ==> MgO + CO2 5.424/2 = approx 2.7 g MgCO3 and approx 2.7 g CaCO3. Starting with these amounts and the equations above, solve for grams CaO and grams MgO, then add ...

Chemistry
Mn changes from +7 on the left to +2 on the right. S(from H2S) changes from -2 on the left to 0 on the right. Show your work if you get stuck.

CHEMISTRY
Two equations which you solve simultaneously. KH2PO4 is the acid(A); K2HPO4 is the base(B) pH = pKa + log B/A So equation 1 is 7.20 = 7.21 + log B/A Solve for B/A = ? Equation 2 is A + B = 1 M. (The problem tells you the buffer is to be 1 M. I like to work in millimols and you...

Chemistry
I'm somewhat confused on how the solubility is being measured; however, this is what I would do. I suspect this is NOT what your prof wants. I would take the 75 C saturated solution. I assume the solubility is 155 g/100 g H2O so that solution will weigh 255 g and contain ...

Chemistry
Adding CuSO4 is adding a common ion (the Cu^2+) so the reaction will shift to the right producing more CuS. Adding Na2SO4 will do nothing. There is no common ion in Na2SO4 and there is nothing to react. So the answer is ........

Chemistry
I agree with you.

Chemistry
(855/180)mols C6H12O6 x (6 mols CO2/1 mol C6H12O6) = (855/180) mols C6H12O6 x (6/1 = ?mols CO2

Chemistry
C6H12O6 + 6O2 ==> 6CO2 + 6H2O mols C6H12O6 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C6H12O6 to mols CO2. Then grams CO2 = mols CO2 x molar mass CO2.

chemistry
mols = M x L = ? Then mols = grams/molar mass. You know mols and molar mass, solve for grams.

Chemistry
110.810 g = liquid + mass cyl -82.450 g = mass empty cylinder -------------- 28.26 g = mass liquid volume liquid = 50 mL density = mass/volume. Check all of the calculations.

Chemistry
There are 454 g/lb There 28317 mL/cubic foot You work this like the last one.

Chemistry
2.36E4 s x (1 min/60s) x (1 hr/60 min) x (1 day/24 hrs) = ?

Chemistry
pH = -log(H^+) Substitute and solve for H^+

Chemistry
C is not right. A buffer consists of EITHER: a. a weak acid with a salt of that weak acid OR b. a weak base with a salt of that weak base. C is a STRONG base and its salt. B is a strong acid D is a strong acid.

Chemistry
Neutral solutions have (H^+)=(OH^-) = 1E-7.

Chemistry
Q = (products)/(reactants) K = (products)/(reactants) reactants ==> products You want products to be higher so is it B or D

chemistry
The Kc is 100 for what reaction? Is it 2SO3 ==> 2SO2 + O2 or the reverse?

chemistry
CH4 + 2O2 ==> CO2 + 2H2O mols CO2 = 11,000/molar mass CO2 = ? Using the coefficients in the balanced equation, convert mols CO2 to mols CH4. Now grams CH4 = mols CH4 x molar mass CH4

Chemistry
Yes. (0.05/30)*100 = ?

Chemistry
The definition gives you the information. The Wikipedia link will give you details. https://www.google.com/search?q=solvay+provess&ie=utf-8&oe=utf-8

Inorganic Chemistry
That is essentially impossible on this forum. I suggest you Google the subject.

Chemistry
I gave you the two balanced half reactions yesterday. Why do I need to this again? C goes from +2 on the left to +4 on the right. Cl is -1 on the left and 0 on the right. Both are oxidized. Nothing wrong with that.

Chemistry
We don't know what the experiment is.

chemistry
You can't make 150 ppm Cu. You can make 150 ppm Cu^2+ 1 ppm = 1 mg/L. 150 ppm = 150 mg/L. So weigh 150 mg Cu, dissolve in a little HNO3, make to the mark in a 1 L volumetric flask with DI water, mix thoroughly, stopper, bingo.

Chemistry
I agree with Bob P but your answer, with that many significant figures, could be counted wrong. b. is right. Same comment about s.f.

Chemistry G.12
I agree with you for a. It TAKES energy to break the crystal lattice. Heat is given off when hydrates are formed. b. I also agree with hydration energy for b. If more energy is given off in forming a hydrate that should increase the solubility.

Chemistry
Since the density is 1.00 g/mL, that makes the mass of solution the same as the volume of the solution. My old standby is to know that 1 ppm = 1 mg/L. 13.7 g pesticide = 13.7 x 1000/250 = approx 55 mg/L = approx 55 ppm. That is the same as approx 55,000 ppb.

CHEMISTRY
MnO4^- + 8H^+ +5e = Mn^2+ + 4H2O 2CHCl3 + 4H2O==> 3Cl2 + 2CO2 + 10 H^+ + 10e Multiply equation 1 by 10; equation 2 by 1 and add,

Chemistry

ap chemistry
It helps us help you if you pick a name, as writeacher suggests, and stick with it. B is not true. All of the others are ok

ap chemistry
K = (products)/(reactants) Let's just say P = 1 and R = 1, then K = 1/1 = 1 and Q = K Now let's change the P and R to say P = 2, then Q = 2/1 so Q>K and P is higher; R is smaller. If P<1, then Q<K and R is higher; P is smaller. Pick the right answer from this...

chemistry -3.2.4
I answered this for you yesterday.

chemistry - 3.1.6
......2HI ==> H2 + I2 I.....1.60.....0....0 C.....-2x......x....x E....1.60-2x...x....x Substitutethe E line into the Keq expression and solve for x.

Chemistry
Is that 0.2512 M stock? I will assume it is. mols NaOH = M x L = ? mols HCl = mols NaOH (since 1 mol HCl = 1 mol NaOH in the balanced equation). M HCL stock = mols/L. You know M and you know mols, solve for L and change to mL if desired.

chemistry - 4.1.4
No. (H^+)(OH^-) = Kw = 1E-14. You know OH, solve for H.

chemistry
NaOH is a strong base.

chemistry
A is not right. K = ([products)/(reactants)

Chem
6.5g/3.0 mL = ?

Chem
CH3COONa.3H2O ==> CH3COO^-(aq) + Na^+(aq) + 3H2O

chemistry
You include but don't "ADD" i. For KNO3 i = 2 delta T = i*Kf*m or delta T = i*Kb*m

Chemistry
I don't get "converted to solid enthalpy"

Chemistry
So why not tell us what you did? That way we could help. This way you just want the answer.

Chemistry
mols C = 12/12 = ? mols Mg = 12/24.3 = ? 1 mol of anything contains 6.02E23 atoms.

chemistry
You can look this up on Google.

chem
w = wavelength 1/w = 1.0973E7(1/1 - 1/n^2). Convert w to meters and solve for n. That gives you n to which the electron moves from the ground state.I get n = 7 Then 1/w = 1.0973E7(1/n^2 - 1/7^2). Convert 2165 nm to m and solve for n. That looks like about 4 to me.

chemistry
I think this is a nonsense question although I suspect you have typed it as it was presented to you. I think the author of this problem probably expects you to answer that you expect more solid than the ion (based on the small number for Ksp); however, the amount of solid AgCl...

chemistry 102
You don't have enough information. I don't know what you did in the experiment.

chemistry
Not enough information to answer. You need to explain what you did.

chemistry
Finding Ka values for these salts is difficult. Intuitively I would think AlCl3 would be more acidic; however, I found Ka for FeCl3 = 2E-3 and for AlCl3 = 1.2E-5. From that information FeCl3 is the stronger. I could find no information about BeCl2 or NiCl3. Sorry I can't ...

chemistry
You started with 25g solution and recovered 4g of salt. So the solubility is 4g per 25g. That would be 4 x 100/25 = solubility in 100 g.

chemistry
what table?

chemistry
I see a lot of posts here. No indication of what you think the answer is. This is a homework help site and not a homework do site. If you have something you don't understand I shall be glad to help you through it if you explain in detail what you're having trouble with...

Chhem
the temperature of the salt water

Chemistry
1.5 + 12.0 = ?

Biochemistry
You should use k1. You are starting with NaHCO3, not Na2CO3. And (base) + (acid) = 0.5M For buffers you want to use a pKa within +/- 1 of the desired pH.

Chemistry
2Na + H2SO4 ==> Na2SO4 + H2 single displacement I'll leave the other one for you. products are Mg3(PO4)2 + H2O It is a double displacement reaction.

Chem
Ag^+(aq) + Cl^-(aq) ==> AgCl(s)

chemistry
Step 1. Write and balance the equation. Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O Step 2. mols Ba(OH)2 = M x L = ? That's approx 0.0046 but you need an accurate answer. Step 3. Using the coefficients in the balanced equation, convert mols Ba(OH)2 to mols HCl. That's approx 0....

Chem
This is a double displacement (or double replacement) reaction. The Mg combines with the Cl to make MgCl2; the OH combines with the H to make H2O.

chemistry
The best answer here is A but that isn't always correct.

chemistry
Generally A but that isn't always correct.

chemistry
Technically this question can't be answered without knowing that the salts have the same ratio of cations to anions.

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