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April 18, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Chemistry
This is a buffer problem. Use the Henderson-Hasselbalch equation.
Tuesday, April 1, 2014 at 11:05pm

Chemistry
jfkl;sdjkfl;asjklfnm,cvjo;sdjflcvuw
Tuesday, April 1, 2014 at 11:02pm

Chemistry
calculate the pH in a solution prepared by dissolving .10 mol of solid NH4Cl in .500 L of .40 M NH3. Assuming no volume change.
Tuesday, April 1, 2014 at 10:50pm

chemistry
24.0 kPa - 1.7 kPa = 22.3 kPa
Tuesday, April 1, 2014 at 10:48pm

chemistry
Assuming the only ingredients could be decomposed to give oxygen (and nothing else) then oxygen driven off must have been 8.9-4.9 = ? Then mol = grams/molar mass.
Tuesday, April 1, 2014 at 10:37pm

chemistry
Yes, your reasoning is flawless and your calculations are superb EXCEPT that you have only two significant figures in 7.1; therefore, you may not have more than 2 s.f. in the answer. So 0.086903 would become 0.087 rounded to 2 s.f. If you omitted a zero on 7.1 than you would ...
Tuesday, April 1, 2014 at 10:34pm

chemistry
My original sample of mixed salt had a mass of 8.9 grams. After heating the mixture in the crucible and weighing it multiple times my final mass of salt ended up being 4.9. How many moles of oxygen were driven off? Lost on how to do this been a while since I have done this.
Tuesday, April 1, 2014 at 10:26pm

chemistry
If my original sample contained 7.1 grams of potassium chlorate. How many moles of oxygen gas would I expect to have evolved? Hint: Convert grams to moles of potassium chlorate, then use the mole ratio in the balanced equation. Balance this equation KClO3 → KCl + O2(g) I...
Tuesday, April 1, 2014 at 10:23pm

AP Chemistry
You're dumb, you don't know how to explain the answer.
Tuesday, April 1, 2014 at 10:21pm

Chemistry URGENT/DR BOB
What valve is the problem talking about? Where is it connected. What does it do. There must be more to the problem than what you've written.
Tuesday, April 1, 2014 at 10:02pm

Chemistry URGENT/DR BOB
Dalton's Law of Partial Pressure consider the following container of helium at 45C. intially the valve is closed. After the valve is opened what is the pressure of the helium gas. your start points are 2.00 atm and 9.00L. after opening the valve you have 3.00 atm and 3.00L...
Tuesday, April 1, 2014 at 9:43pm

chemistry
1. mols P = grams/molar mass 2. Convert mols P to mols P4O10 using the coefficients in the balanced equation. 3. Convert mols P4O10 to g. g = mols x molar mass.
Tuesday, April 1, 2014 at 9:36pm

Chemistry 2
ethyl acetate + water ---> ethyl alcohol + acetic acid Once stoppered and allowed to reach equilibrium again. It will be in the reverse direction ethyl alcohol will react with acetic acid to form water and ethyl acetate
Tuesday, April 1, 2014 at 9:30pm

chemistry
How you solve P4(s)+5O2(g)------>P4O10(g) .if 2.50 grams of phosphorus is ignited in a flask how many grams of P4O10 are formed ?
Tuesday, April 1, 2014 at 9:22pm

Chemistry URGENT
Not only are you confused, surely you didn't post all of the question. You need to rephrase the question so that it is clear.
Tuesday, April 1, 2014 at 9:07pm

Chemistry
HCl + KOH ==> KCl + H2L mols KOH = grams/molar mass mols KOH = mols HCl from the 1:1 ratio (coefficients) in the balanced equation. Then M HCl = mols HCl/L HCl. You know mols and M, solve for L and convert to mL.
Tuesday, April 1, 2014 at 9:04pm

Chemistry
How many milliliters of 0.326 M HCl would be required to titrate 5.48 g KOH?
Tuesday, April 1, 2014 at 8:28pm

Chemistry URGENT
consider the following container of helium at 45C. intially the valve is closed. After the valve is opened what is the pressure of the helium gas. your start points are 2.00 atm and 9.00L. after opening you have 3.oo atm and 3.00L. The answer is 2.25 atm what formula did you ...
Tuesday, April 1, 2014 at 7:57pm

Chemistry
30 grams
Tuesday, April 1, 2014 at 7:52pm

Chemistry
Two stoichiometry problems; one for Cu(OH)2 to CuSO4 and one for Cu(OH)2 to NaOH. Stoichiometry problems, for the most part, are worked the same way. Step 1. Convert what you have (100 g Cu(OH)2 to mols. mols = grams/molar mass = ? Step 2. Convert mols Cu(OH)2 to mols NaOH. ...
Tuesday, April 1, 2014 at 7:09pm

chemistry
Ba(OH)2 + 2HNO3 ==> Ba(NO3)2 + 2H2O mols HNO3 = M x L = ? mols Ba(OH)2 = 1/2 that from the coefficients in the balanced equation. Then M Ba(OH)2 = mols Ba(OH)2/L Ba(OH)2. YOu know mols and L, solve for M.
Tuesday, April 1, 2014 at 7:03pm

Chemistry
mols K2Cr2O7 = grams/molar mass Then M = mols/L solution. You can use this information to calculate the concn of the Fe^2+ in the 10.00 mL sample of unknown ferrous solution BUT you won't now the concn of the original without knowing what the original volume was.
Tuesday, April 1, 2014 at 6:59pm

Chemistry
AgCl--->Ag^(+)+Cl^(-) AgNO3= 2E^-4L*0.15mol/L AgNO3/(.01L)=mol/L AgNO3=mol/L Ag^(+)=.003M Find Ksp(AgCl) in solubility constant table Ksp(AgCl)=1.77E-10 1.77E-10=[.oo3M Ag(+)][Cl^(-)] solve for Cl^(-) Cl^(-)=5.9E-8M 5.9E-8mol/L*.01L in tank * mm 35.453 g/mol=2*10^-8 g
Tuesday, April 1, 2014 at 6:41pm

Chemistry
:You have to assume a reaction, and balance it. N2H4 + O2>>N2 + 2H2O looks like twice as much as 4.2L
Tuesday, April 1, 2014 at 6:38pm

Chemistry
a. figure the mole mass of IronIII oxalate. M=mass/molmass*1/.125 b. Look at the formual for iron III oxalate. Are there three oxalate ions for each molecule of IronIII oxalate? So multiply a. above by 3.
Tuesday, April 1, 2014 at 6:35pm

Chemistry
a solution is prepared by dissolving 3.7500grams iron(III) oxalate in enough water to make 125.00mL of solution. 1. what is the molar concentration of iron(III) oxalate in this solution? 2. what is the molar concentration of oxalate ions in this solution?
Tuesday, April 1, 2014 at 5:40pm

Chemistry
a potassium dichromate is prepared by 0.3525grams of K2Cr2O7 is enough water to yield 250.0mL of solution. a student then measures 10.00mL of an unknown solution of Fe2+ into an erlenmeyer flask and dilutes with 90mL of 1.0M hydrochloric acid. she then titrates this sample ...
Tuesday, April 1, 2014 at 5:37pm

Chemistry
At STP, if 4.20L of O 2 reacts with N2H4 how many liters of water vapor will be produced?
Tuesday, April 1, 2014 at 5:11pm

chemistry
The molarity of an aqueous solution of barium hydroxide is determined by titration against a 0.335 M nitric acid solution. If 32.8 mL of the base are required to neutralize 21.5 mL of nitric acid, what is the molarity of the barium hydroxide solution?
Tuesday, April 1, 2014 at 4:32pm

Chemistry
2NaOH + CuSO4 = Na2SO4 + Cu(OH)2 100g of Cu(OH)2 is needed. Assuming 100% yield, how much of 1M NaOH and 0.5M CuSO4 must be used in mL? Any help would be awesome- even a formula on how to solve
Tuesday, April 1, 2014 at 4:20pm

Chemistry
C6H12O6 ==> 3C2H4O2
Tuesday, April 1, 2014 at 3:39pm

chemistry
mols CO2 grams/molar mass CO2 = about 7.7 = mols C. mols H2O = grams/molar mass H2O = 138/18 = about 7.7 so mols H atoms is twice that or about 15.4 Now find the ratio. The easy way is to divide everything by the smaller numbr C = 7.7/7.7 = 1.00 H = 15.4/7.7 = 2.00 So ...
Tuesday, April 1, 2014 at 3:37pm

Chemistry !
See your other post.
Tuesday, April 1, 2014 at 3:19pm

chemistry
Unsure how to solve this without a formula... I think its combustion analysis? CxHy + O2 --> CO2 + H20 CxHY has a MW=78g/mol. 100g of CxHy yields 338g CO2 and 138g of H2O. What is the formula CxHY (what are x and y)? Balance the reaction equation. Any help at all is ...
Tuesday, April 1, 2014 at 3:17pm

Chemistry
yes I apologize, #1 is C6H12O6 --> C2H4O2 thankyou for all your help!
Tuesday, April 1, 2014 at 3:15pm

Chemistry
I disagree that the half reaction method is easier in all circumstances; in fact, I think it is harder to do them this way for these three than straight trial and error. Let me illustrate on the last one. Here is what I do. C2H6O + O2 ==> CO2 + H2O I look and see 2C on the ...
Tuesday, April 1, 2014 at 3:11pm

Chemistry
Having trouble balancing redox equations. Teacher says I should use the method of half reactions and I'm not sure how. Any explanation or formula would be nice. C6H12O2 --> C2H4O2 SO2+H2O+O2 --> H2SO4 C2H6O+O2 --> CO2 + H2O
Tuesday, April 1, 2014 at 2:21pm

chemistry
Oxidation is the loss of electrons. Reduction is the gain of electrons. Zn is +2 on the left and +2 on the right. H is +1 on the left and +1 on the right. O is -2 on the left and -2 on the right. Cl is -1 on the left and -1 on the right. Anything change? nope. So nothing is ...
Tuesday, April 1, 2014 at 2:02pm

chemistry
In the reaction ZnO+2HCl=ZnCl2+H2O what is oxidized and what is reduced?
Tuesday, April 1, 2014 at 12:47pm

AP CHEMISTRY
uju
Tuesday, April 1, 2014 at 12:32pm

chemistry

Tuesday, April 1, 2014 at 11:05am

Chemistry !
The solubility of Mn(OH)2 is 3.04 x 10^-4 gram per 100 ml of solution . A) write the balanced chem equation for Mn(OH)2 in aqueous solution B) calculate the molar solubility of Mn(OH)2 at 25 degrees celcius C) calculate the value of the solubility product constant, Ksp, for Mn...
Tuesday, April 1, 2014 at 10:26am

Chemistry - Solubility
Given: Concentration of HCl is 0.1388M 0.5 g of Ca(OH)2 was placed in a flask. 100mL of 0.05M NaOH was poured into the flask. 25mL aliquot was filtrated and used for titration. Suppose to calculate the OH^- equilibrium concentration from the titration data, as well as the OH...
Monday, March 31, 2014 at 11:11pm

Chemistry
1 c 2 a 3 d 4 b
Monday, March 31, 2014 at 11:09pm

Chemistry - Solubility
0.5 g of Ca(OH)2 was placed in a flask. 100mL of 0.05M NaOH was poured into the flask. 25mL aliquot was filtrated and used for titration. Suppose to calculate the OH^- equilibrium concentration from the titration data, as well as the OH^- from the original solution. Then ...
Monday, March 31, 2014 at 11:06pm

Chemistry - Solubility
I must confess I don't understand this at all.
Monday, March 31, 2014 at 10:55pm

Chemistry - Solubility
INFORMATION: [HCl] = 0.1388 M We placed 0.5 g Ca(OH)2 in 100 mL of the following solutions: A 25 ml aliquot was used Flask A: Distilled Water (7.4 mL of HCl needed to titrate) Flask B: 0.05 M NaOH (7.5 mL of HCl needed to titrate) Flask C: 0.025 M NaOH (10.8 mL of HCl needed ...
Monday, March 31, 2014 at 10:45pm

Chemistry - Solubility
Also a 25 ml aliquot was used.
Monday, March 31, 2014 at 10:43pm

Chemistry - Solubility
INFORMATION: [HCl] = 0.1388 M We placed 0.5 g Ca(OH)2 in 100 mL of the following solutions: Flask A: Distilled Water (7.4 mL of HCl needed to titrate) Flask B: 0.05 M NaOH (7.5 mL of HCl needed to titrate) Flask C: 0.025 M NaOH (10.8 mL of HCl needed to titrate) Flask D: 0....
Monday, March 31, 2014 at 10:38pm

chemistry
I guess A is one atom, B is another atom, what's n. Perhaps the number of B atoms? Or is that supposed to stand for the number of unpaired electrons?
Monday, March 31, 2014 at 10:38pm

Chemistry
5.13
Monday, March 31, 2014 at 10:30pm

chemistry
qwater = mass H2O x specific heat H2O x (Tfinal-Tinitial) Note: Tfinal-Tinitial = delta T = 10.20 C.
Monday, March 31, 2014 at 9:52pm

chemistry
its the ABn molecules, which is related to VSPER
Monday, March 31, 2014 at 9:52pm

chemistry
what's abn mean?
Monday, March 31, 2014 at 9:50pm

chemistry
what are the favored geometrical arrangements for abn molecules which the A atom has 2, 3, 4, 5 and 6 pairs of electrons in its valence shell?
Monday, March 31, 2014 at 9:47pm

chemistry
How much heat (in Joules) is gained by the water when a chemical reaction takes place in 100.0 ml aqueous solution, has a temperature increase of 10.20°C and a specific heat capacity of 4.180 J/°Cg? [Hint: ignore any effects of the calorimeter and solve for qwater]
Monday, March 31, 2014 at 9:44pm

chemistry
shouldn't it be -2x?
Monday, March 31, 2014 at 9:05pm

Chemistry
I can't type this in the format you want because the site won't handle it. So n1 will be a and n2 will be b. 1/wavelength = R(1/a^2 - 1/b^2) n1 = a = 1. 1^2 = 1 n2 = b = 3. b^2 = 9 1/wavelength = R(1/1 - 1/9). R = 1.0973E7 wavelength will be in meters. Then E = hc/...
Monday, March 31, 2014 at 8:46pm

Chemistry
Calculate the energy associated with the photon that would be released when an H electron falls fro the n=3 energy level to the n=1 energy level. show work if possible so I can understand how to do it. Thanks in advance!!!
Monday, March 31, 2014 at 8:39pm

chemistry
what is the total mass of Rn-222 remaining in an original 160-mg sample of Rn-222 after 19.1 days?
Monday, March 31, 2014 at 7:25pm

Chemistry
jh
Monday, March 31, 2014 at 7:14pm

chemistry
Let CH3COOH = HAc .......HAc + NaOH = NaAc + H2O At the equivalence point you have NaAc, sodium acetate. The acetate ion (C2H3O2^- or Ac^-) is hydrolyzed as follows and I assume that is solid NaOH placed in the acetic acid, there is no volume change, and (Ac^-) = 1M: ............
Monday, March 31, 2014 at 6:31pm

Chemistry
Same process + a little more from the NaN3 problem above. Find mols aspirin produced by 100 g salicylic acid, convert to grams aspirin, and that is the theoretical yield. Then % yield = (actual yield/theoretical yield)*100 = ?
Monday, March 31, 2014 at 6:16pm

Chemistry
2NaN3 ==> 2Na + 3N2 mols N2 gas = grams/molar mass = x mols N2 Using the coefficients in the balanced equation, convert mols N2 to mols NaN3. That's x mols N2*(2 mols NaN3/3 mols N2) = x mols N2*(2/3) = ? mols NaN3. Then ? mols NaN3 x molar mass NaN3 = grams NaN3.
Monday, March 31, 2014 at 6:13pm

Chemistry
The chemical reaction for the generation of gas in an automobile safety air bag is 2NaN3(s)→ 2Na(s)+3N2(g) What volume of gas is produced if there are 130.0 grams of NaN3 used in the reaction? (The density of nitrogen gas is 0.916 g/L.) Please show your work.
Monday, March 31, 2014 at 4:52pm

Chemistry
The chemical reaction of 100 g of salicylic acid, C7H6O3, with excess acetic anhydride produces 50.0 g of aspirin, C9H8O4, according to the equation. What is the percentage yield for the reaction shown below? Please show your work. C7H6O3+C4H6O3→C9H8O4+C2H4O2
Monday, March 31, 2014 at 4:48pm

chemistry
In freezing, the stronger attraction that results in closer/shorter bonds (though the overall density increase due to the highly ordered structure) than in melting water so the potential energy is lower.
Monday, March 31, 2014 at 4:29pm

chemistry
Freezing and melting are two different physical changes that involve the same amount of energy. In an exothermic reaction, the amount of energy in the reactants is higher than the resulting amount of energy in the products. This means that the line graph starts at a higher ...
Monday, March 31, 2014 at 4:28pm

chemistry
A 1.0 M acetic acid solution (CH3COOH, pKa = 4.7) is neutralized by dissolving NaOH(s) (a strong base) in the solution. Estimate the pH at the equivalence point of the neutralization process: 4.7 7.0 9.3 Which one of the following statements best explains your prediction? 1. ...
Monday, March 31, 2014 at 4:23pm

chemistry
So I do all the typing and thinking while you compare. That takes up my time so I can't answer other questions. It's better for you to do all the typing and thinking and let me compare. Much more efficient process.
Monday, March 31, 2014 at 4:11pm

Chemistry 2
I might add that the excess heat (but light also may be involved) is absorbed by the surroundings in exothermic reactions. Next, you need to talk about endothermic reactions and how the heat needed to make the reaction go is supplied by the surroundings.
Monday, March 31, 2014 at 4:08pm

chemistry
Can you answer it please? I just want to compare my answer..
Monday, March 31, 2014 at 4:01pm

Chemistry 2
I just wanted to compare my answer with the answer that i will be getting.. This is what I have: Exothermic reaction starts at a higher energy value and ends at a lower energy value. In an exothermic reaction, we know that energy is given off in the form of heat. This energy ...
Monday, March 31, 2014 at 3:59pm

Chemistry
mols = grams/molecular weight
Monday, March 31, 2014 at 3:58pm

chemistry
Another discussion question.I shall be happy to critique your work.
Monday, March 31, 2014 at 3:57pm

Chemistry 2
This is a long discussion question. How would you like us to help you with this assignment?
Monday, March 31, 2014 at 3:56pm

Chemistry
Absolutely false. It will increase the solubility BECAUSE of the formation of the complex Ag(NH3)2Cl AgCl + 2NH3 ==> Ag(NH3)Cl
Monday, March 31, 2014 at 3:55pm

Chemistry
Use the Henderson-Hasselbalch equation and the total buffer (both equations) and solve simultaneously. 7.45 = 7.21 + log (base/acid) I get base/acid = estimated 1.8 but you need to do it more accurately. And base + acid = 1M Solve simultaneously. I obtained approximately 0.36M...
Monday, March 31, 2014 at 3:53pm

Chemistry
The presence of ammonia in a solution of AgCl will decrease the solubility of AgCl. True Or False
Monday, March 31, 2014 at 3:47pm

Chemistry 2
Compare endothermic and exothermic reactions in terms of potential energy, heat flow, and observed temperature changes. Explain your answer in complete sentences.
Monday, March 31, 2014 at 3:44pm

chemistry
Freezing and Melting are two different physical changes that involve the same amount of energy. compare and contrast the potential energy diagrams that would represent each of these processes. Be specific in your comparison.
Monday, March 31, 2014 at 3:40pm

chemistry
help
Monday, March 31, 2014 at 3:37pm

chemistry
Hg22+ ==> 2Hg2+ + 2e Hg22+ + 2e ==> 2Hg
Monday, March 31, 2014 at 3:36pm

Chemistry
1/wavelength = R*(1/4 - 1/x^2) Convert wavelength to meters. You know R, the 1/4 is 1/2^2. X will be the higher orbit.
Monday, March 31, 2014 at 3:23pm

chemistry
Ptotal = pH2O + pgas 745 mm = pH2O(look up vapor pressure H2O @ 26 C) + pgas. Solve for pgas which is the pressure of the DRY gas. Then PV = nRT. You know P (use pressure of dry gas), n, R, and T; solve for V in liters.
Monday, March 31, 2014 at 3:22pm

chemistry
Li2O + HOH ==> 2LiOH mols H2O = 85,000/18 = estimated 4722 Now convert mols H2O to mols Li2O using the coefficients in the balanced equation. That's estimated 4722 x (1 mol Li2O/1 mol H2O) = about 4722 mols Li2O. Now convert that to g Li2O. g = mols x molar mass. Go ...
Monday, March 31, 2014 at 2:57pm

chemistry
Just like the HBr problem.
Monday, March 31, 2014 at 2:46pm

chemistry
(HBr) = 3.20mols/21.3L = about 0.150 but that's an estimate. It's just like it sounds. I = initial; C = change; E = equilibrium. I assume you made a typo and meant Br2. ..........H2 + Br2 ==> 2HBr I.........0.....0......0.150 C.........x.....x.......-x E.........x...
Monday, March 31, 2014 at 2:46pm

chemistry
(NO) = 2.8E-2/1.4L = about 0.02M (Cl2) = 1.4E-3/1.4L = about 0.001M (NOCl) = 5.9/1.4L = about 4.21 Qc = (NOCl)^2/(NO)^2*(Cl2) Qc = (4.21)^2/(0.02)^2*(0.001) = approx 5E7 but you should confirm that. Compare that with Kc =1E7 Qc > Kc; therefore, numerator is too large and/or...
Monday, March 31, 2014 at 2:41pm

Chemistry
A helium ballon contains 0.32g of helium. Given the molecular weight of helium is 4. How many moles of helium does it contain.
Monday, March 31, 2014 at 2:29pm

chemistry
2NO (g) + Cl2 (g) <=> 2NOCl (g) (reversible) equilibrium constat = 1 x 10^7 @ certain temp NO = 2.8 x 10^-2 mol Cl2 = 1.4 x 10^-3 mol NOCl = 5.9 mol all mixed in a 1.4 L flask what is Qc and what direction will system go?
Monday, March 31, 2014 at 12:47pm

chemistry
equilibrium constant = 2.180 x 10^6 @ 730 C. H2 (g) + Br (g) <=> 2HBr (g) (reversible) startin with 3.20 moles of HBr in a 21.3-L reaction vessel, calculate the concentrations of H2, Br2, and HBr at equilibrium idk how to start my ice table
Monday, March 31, 2014 at 12:45pm

chemistry
equilibrium constant = 55.3 @ certain temperature H2 (g) + I2 (g) <=> 2HI (g) (reversible) If you start with 0.195 M hydrogen iodide, what will the concentrations of H2, I2, and HI be at equilibrium?
Monday, March 31, 2014 at 12:43pm

Chemistry
qwerty
Monday, March 31, 2014 at 12:14pm

chemistry
H2O -> dispersion forces, dipole-dipole forces, hydrogen bonding. BrCl -> dipole-dipole forces.
Monday, March 31, 2014 at 10:05am

chemistry
H2O -> dispersion forces, dipole-dipole forces, hydrogen bonding. BrCl -> dipole-dipole forces.
Monday, March 31, 2014 at 10:05am

chemistry
How many grams of Li2O must be carried on board to remove 85.0kg of water?
Monday, March 31, 2014 at 9:38am

chemistry
Assume that 0.0200 mole of a gas is collected in the lab by water displacement. If the temperature of the gas is 26.0oC and the total pressure in the gas tube is 745 mm Hg (including water vapor), what is the volume in liters of the dry gas? (Use the ideal gas law.)
Monday, March 31, 2014 at 3:20am

Chemistry
0.189
Monday, March 31, 2014 at 3:15am

Chemistry
In the spectrum of a specific element, there is a line with a wavelength of 656 nm. Use the Rydberg equation to calculate the value of n for the higher energy Bohr orbit involved in the emission of this light. Assume the value for the lower energy orbit equals 2.
Monday, March 31, 2014 at 2:35am

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