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Posts by DrBob222

Total # Posts: 54,507

Chemistry
g Mg changed = 6.00 - 4.50 = 1.50 mols Mg = grams/atomic mass = ? Then rate = delta mols/delta time.

chemistry
...CO3^2- + HOH ==> HCO3^- + OH^- I..0.145..............0......0 C...=x................x......x E.0.145-x.............x......x Kb for CO3^2- = (Kw/k2 for H2CO3) = (x)(x)/(0.145-x) Solve for x = (OH^-)

Chemistry
q = mass Ag x specific heat Ag x delta T. Substitute and solve for dT.

Chemistry
q = mass H2O x specific heat H2O x (Tfinal-=Tinitial) You know mass H2O, you can look up specific heat H2O and you are given Tfinal and Tinitial. Substitute and solve for q and that will be enthalpy for 0.882 g CO or J/0.882. Convert that to J/mol. J/0.882 x (28g/mol) = dH in ...

Chemisty
A limiting reagent (LR) and excess reagent (ER) problem. You know that because amounts are given for BOTH reactants; besides, the problem tell you. Convert 6.25 g NH3 to mols. mols = grams/molar mass Do the same for O2. Using the coefficients in the balanced equation, convert ...

@ Bob Pursley--Chemistry
Sorry I posted too. I was almost through answering when the phone rang and when the conversation was over I didn't check if the question had been answered.

Chemistry
The equation tells you that 2 mols SO2 will generate 197.8 kJ. How much is 2 mols SO2? That's 2*64 = 128 g SO2 will generate 197.8 kJ. So what will 8.54 g do? Set up a ratio/proportion or use reason to do it. Here is ratio/proportion: (128 g/197.8 kJ) = 8.54 g/x kJ). Solve...

Chemistry
The rate of decomposition of the ammonium salt to produce gaseous NH3 is so slow at room temperature that the test for NH3 might be missed; therefore, the solution is heated in order to increase the rate of reaction. For many reactions the rule of thumb is that the rate is ...

Chemistry
Without know the experiment you did I must guess about some of these. 1. Most nitrates decompose when heated to give oxygen gas. 2. I don't knopw either unless you want to make sure the solution is basic. 3. How would you know what gas is liberated if you don't test it...

Chemistry
Good luck. I believe you have too many unknowns.

Chemistry
No. M = mols/L mols = grams/molar mass Substitute and solve for M.

chemistry
????

chemistry
(p1/t1) = (p2/t1). Substitute and solve. You don't have t1 listed.

AP Chemistry!!!
I don't get it. You have it worked out in your mind. Heat lost by Al is q = mcdT. Heat gained by water is q = mcdT. heat lost by Al + heat gained by H2O = 0 so you never need to find q by itself. [5.6 x specific heat Al x (Tf-Ti)] + [mass H2O x specific heat H2O x (Tf-Ti...

Chemistry
Ptotal = pdry ice + pH2O Substitute total land pH2O, then solve for pdry ice.

chemistry
Zn + 2HC2H3O2 ? Zn(CH3COO)2 +H2

Chemistry
I assume table 10-1 lists the density of the materials in the list of possible metals. density = mass in air/(mass in air-mass in H2O)= ? Compare with the numbers in table 10-1

science
https://www.quora.com/Are-there-any-good-conductors-of-heat-that-are-not-metals

chemistry
I don't see a question here.

Chemistry
isotopes

Chemistry
A = kc A = 0.82 k = 6220. Solve for c in mols/L. Correct for the two dilutions; i.e., 1 up to 3 and 1 up to 5 and the answer is in mols/L. Convert that to ng/L, then to ng/100 mL.

Chemistry
Who knows? You don't give any details.

Chemistry
The noble gases.

AP Chemistry!!!
Al ==> Al^3+ + 3e Pb^2+ + 2e ==> Pb Oxidation is the loss of electrons. Reduction is the gain of electrons. Which half rxn above lost and which gained? For the potential of the cell, look up the reductions potentials, change the sign of the Al half cell, add in the ...

Chemistry
Both are done the same way. Here is how to do the first one. How many mols do you need? That's mols = M x L = ? Then mols = g/molar mass. You know molar mass and mols, solve for grams Pb(NO3)2 or NaI needed.

Chemistry (PLZ HELP)
There is nothing wrong with the solution by MathMate of this hypotehtical question. However, I just don't believe Al2O3 will decompose thermally to Al/

Chemistry
20 mL NH3 x 0.5 M NH3 = mL HCl x 0.1 M HCl. Solve for mL HCl.

Chemistry
What's problem 1?

Chemistry
Use the Henderson-Hasselbalch equation.

Chemistiy
I don't get it, the possible answers that is. Voltaic cell is the correct answer to a. Voltaic cell is the correct answer to b.

Chemistry (just need someone to check my answer)
9 mols O2 is correct; I don't see a balanced equation.

chemistry
Use the Arrhenius equation.

Chemistry
When using solid KOH, the volume of the solution doesn't change significantly and delta T will be some value. When adding a solution of KOH, the volume of the KOH will add to that of the HCl; therefore, the heat generated must heat a larger about of water and delta T will ...

AP Chemistry
I don't think you have the right picture. Do it this way. mols WO3 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols WO3 to mols CO2. Now convert mols CO2 to grams CO2. g CO2 = mols CO2 x molar mass CO2. This gives you the grams of CO2 ...

Chemistry
You're right but I would have done it as (0.68/1.3) = 0.52 = 52%. I'm not being picky, rather, I'm pointing out that if I do it your way I'm doing two operations that are not necessary (multiplying both numerator and denominator by 1000 before dividing) and ...

Chemistry
You have 2 mols Al and 3 mols C and 9 mols O.

Chemistry
Again, I assume this is ppm w/v. Volume of 25 kg seawater is v = m/d = 5000 g/1.025 g/mL = 4878 mL. Then mg Pb/L = ? mg/L = ppm w/v

Chemistry
I assume that is ppm w/v. 5 ppm = 5 g Pb/10^6 g H2O = 5 mg Pb/10^3 g H2O = 5 mg Pb/1000 g H2O = 5 mg Pb/1L H2O if density of H2O is 1.00 g/mL (or 1000 kg/m^)

Organic Chemistry
You might think so since acetone has such as low boiling point; however, I might be worried more that the flask was heated too much in trying to get all of the solvent out. You might try dissolving the solid again in a minimum of solvent, pouring the mixture into a beaker, ...

Chemistry
The longer the chain the more intermolecular forces and the higher the boiling point (lower vapor pressure).

Chemistry
mols Fe ==> grams/molar mass = ? Convert to mols O2. That's ?mols Fe x (3 mols O2/4 mols Fe) = ? Then mols O2 x 22.4 L/mol = L O2

Chemistry
What's an IRF? 2NaOH + H2SO4 = Na2SO4 + 2H2O Convert pH of NaOH to pOH and calculate (OH^-) and (NaOH). Then mols NaOH = M x L = ? mols H2SO4 = M x L = ? Subtract to see which is in excess, calculate (H^+) or (OH^-) as it applies and convert to pH.

Chemistry
Are you sure of that formula? mols = 8.87/molar mass = ? Then M = mols/L. YOu know mols and M, solve for mL.

Chemistry
The carbon dioxide is released from the solution. At room temperature CO2 isn't very soluble in water.

chemistry
If you want to dilute the solution from 5 M to 0.5 M, you must dilute by a factor of 10. You want 100 so take 10 mL and dilute to 100. For this you will need a 10 mL pipet and a 100 mL volumetric flask. 2. Powdered Zn has MUCH MORE surface area so the reaction is faster (MUCH ...

Chemistry
We can't draw structures on this forum. I suggest you google this. Most Lewis structures on on the web.

Chemistry
P*molar mass = density*RT P must be in atm. 760 torr = 1 atm.

Chemistry
I have no idea what the domino format is.

chemistry
https://en.wikipedia.org/wiki/Lead(II)_iodide

Chemistry
You can find the answer easily by googling scintillation counter. Wilipedia is the best sorce, I think, and you should read under "detectors".

Chemistry
I don't think it will change the position at all although your prof may be expecting an answer of D. To make it shift to the left you must add Ag+ or S2- and neither is present in (NH4)2SO4. To shift to the right you must add something that reacts with either product but (...

Chemistry
What's the problem here? Do you know the definition of Keq?

Chemistry
B is not right.

Chemistry
temperature

CHEMISTRY
The volume of H2 depends upon how much Zn you started with. You don't have that in the problem.

General
It's well and good.

Chemistry
rate O2 = 1L/37 hrs = 0.027 L/hr. rate unk = 1L/26 hrs = 0.38 L/hr. (rO2/runk)= sqrt(Munk/MO2) Substitute and solve for Munk. cheers from my boy.

Chemistry
3G +2M ==> G3M2 mols M = 5.00/135 = approx 0.037 mols G = 0.037 x (3 mols G/2 mols M) = approx 0.0555 Then mols = g/atomic mass. You know mols G and grams G, solve for atomic mass G. I'll bet you get 36.

Chemistry
The HH equation calculates this directly.

chemistry
Great but volumes of what? What kind of formic acid solution do you have? What kind of sodium formate solution do you have.

College Chem 2
Something is amiss here. The Ksp is the Ksp. You can't have two Ksp values for Ag2CrO4.

chemistry
22 servings/box x 90 mg K/serving = ? mg K/box. Convert to g. Convert to mols. mols = grams/atomic mass = ?

chemistry
Convert 10 lb to grams. 10 lbs x (?g/lb) = ? grams sugar. Then mols sugar = grams/molar mass = ?

Chemistry
What you REALLY mean is H2SO4 (sulfuric acid) and Na2CO3 (sodium carbonate). H2SO4 + Na2CO3 ==> H2O + CO2 + Na2SO4 mols Na2CO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Na2SO4 to mols H2SO4. You can see that is a 1:1 ratio. Then M ...

chem
.NH2COONH4(s) --> 2NH3(g) + CO2(g) I..................0.........0 C.................2x.........x E.................2x.........x First, remember the solid doesn't enter into Keq. Second, you know , if x = pressure, that 2x + x = 3 which makes 1 = x, which means pNH3 = 2 ...

chem
D is right BUT you have a SERIOUS error in what you wrote. Ksp expression is not what you wrote. Ksp = (Ca^2+)^3*(PO4^3-)^2. Note that you don't have that. Here is the problem. Ca3PO4 ==> 3Ca^2+ + 2PO4^3- I...........0........0 C...........3S.......2S E..........3S...

chemistry
ammonium sulfate is (NH4)2SO4 and not what you have. So if 13.2 g (NH4)2SO4 is 0.088 mols, the you get 0.099 mols SO4^2- and 2*0.099 mols NH4 for a total of ?? mols.

chemistry ksp
See my response to your post above.

chemistry
See my response to your post above.

Chemistry
Choose any convenient volume such as 100 mL. Then calculate millimols each. mmol = mL x M = ? H^+ for pH 3 = 1E-3 H^+ for pH 4 = 1E-4 H^+ for pH 5 = 1E-5 mmols pH 3 = 100 x 1E-3 mmols pH 4 = 100 x 1E-4 mmols pH 5 = 100 x 1E-5 M when mixed = total mmols/total mL. It doesn't...

Chemistry
pH = -log(H^+)

chemistry
0.50 mol/dm^3 = 0.5 M 200 cc = 0.2 L = 0.2 dm^3 mols you want Cl^- = M x L = 0.5 x 0.2 = 0.1 mol Cl^- Convert mols Cl^- to mols CaCl2. 0.1 mol Cl^- x (1 mol CaCl2/2 mols Cl^-) = 0.05 mol CaCl2. Now convert mols CaCl2 to grams. mols = grams/molar mass. You kow mols and molar ...

chemistry
Note: L is liter. K is kelvin.

Chemistry
The ion electron method OR The half reaction method.

Chemistry
2 KClO3 (s) ? 2 KCl (s) + 3 O2 (g) Use PV = nRT and solve for mols O2 at the conditions listed. Using the coefficients in the balanced equation, convert mols O2 to mols KClO3. Convert mols KClO3 to grams by g = mols x molar mass Then %KClO3 = (mass KClO3/mass sample)*100 = ?

Chemistry
Do you mean, What is the name? Strontium permanganate

Chemistry
Use PV = nRT For P use Ptotal = pH2O + pgas.

Chem
Reason it out. Use the equation. That tells you that 1 mol Mg (that's 24.3 grams Mg) evolves 466.85 kJ. So what will 5.00 g Mg evolve? You can set up a ratio/proportion or use 466.85 kJ x (5.00 g/24.3g) = ? kJ. The ratio/proportion looks like this. (5.00/24.3) = (x kJ/466....

chemistry chem check
I don't think so. Isn't it true that the vapor phase is enriched in the more volatile solvent?

Chemistry
hbl, I think you jumped the gun. mols CaCO3 = 1/2 mols HCl as Bob P wrote. He assumed you would be able to convert mols to grams. Then mass CaCO3 = mols CaCO3 x molar mass CaCO3 = ?

Chemistry
Fe2O3 + 2Al = Al2O3 + 2Fe mols Fe2O3 ==> grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe2O3 to mols Al2O3. Now convert mols Al2O3 to grams Al2O3. g = mols x molar mass = ?

Chemistry
mols Al2O3 = ? Convert mols Al2O3 to mols Al Convert mols Al to grams Al. See your post above if you need refreshing. Same process. All of these stoichiometry problems are done the same way.

Chemistry
See your other posts.

chemistry
1/wavelength = RZ^2(1/1^2 - 1/infinity) R is Rydberg constant. You can look that up in (in meters) The term of 1/infinity will be zero. This will give you wavelength and you can convert to energy with E = hc/wavelength. Z is the atomic number of Be

Chemistry
PV = nRT R is 0.08206 T in kelvin V in liters. P in atmospheres.

Chemistry (equlibrium direction) urgent
You're right. There are 2 mols gas on the left and 2 mols gas on the right; therefore, pressure has no effect. You're right again on the catalyst. A catalyst will change the speed of a rxn but not the equilibrium point (that is, the rxn will get to equilibrium faster) ...

chemistry
The simple thing to do is to ignore it. It's a spectator ion. The rxn is between the chromate ion and the ferrous (FeII) ion.

chemistry
The procedure for working stoichiometry problems. 1. Write and balance the equation. You have that. 2. Convert whatinformation you have (you want 50 g Na3PO4) into mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols Na3PO4 to mols...

chemistry
The following procedure will work these stoichiometry problems. 1. Write and balance the equation. You have that. 2. Convert What you have (C2H6) to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols what you have (C2H6) to mols ...

chemistry
When dealing with gases we can use a shortcut and use L as if it were mols. 900 L NO2 x (1 mol NO/3 mols NO2) = ?

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

chemistry
I am extremely curious about how the systematic name for NH4Br ties in with the mass of ethane.

University
Your post isn't clear to me at all. It appears you want to know the concn of the H2SO4 but the word "matter" in there makes no sense at all. Try rephrasing the question and this time proof what you've written. Thanks.

Chemistry
A buffer is a combination of a weak acid and the salt of its salt (acetic acid and sodium acetate) or a weak base and its salt (NH3 and NH4Cl). Buffers resist a change in pH. Here is how an acid buffer works. Say it is HAc and Ac^-. If a strong acid, such as HCl is added, the ...

chemistry chem check
I don't think so. When Raoult's Law tells you that the vapor pressure of a pure solvent is lowered when a non-volatile solvent is added. mols solute = 0.4 mols solvent = 0.8 total mols 1.2 Xsolvent = 0.8/1.2 = ? Then pmixture = Xsolvent*Po solvent. So it must be either...

chem
You don't have enough info posted to answer this question. If you know grams CO2 or mols CO2, use PV = nRT and solve for V.

chemistry
What are you using to make the HCl?

Chemistry
If I work this out I find that the water of crystallization(s) are not whole numbers. There are compounds where the hydration number is not a whole number. Do you have any indication that this is the case for this problem.

Chemistry
1. Working in millimols. mmols NaoH added = 55 x 1.1 = 60.5 ......HAc + OH^- ==> Ac^- + H2O I.....400...0.........400 add........60.5............... C..-60.5..-60.5.......+60.5 E...339.5...0........460.5 Convert the E line (in mmols) to M with M = mmols/total mL. Total mL...

Chemistry
See your other post.

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