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April 23, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Chemistry
Great, good luck !
Thursday, February 27, 2014 at 7:08pm

Chemistry
That is why both Steve and I asked what the pressure was for the air in problem 1. The density of air or any gas depends strongly on Temp and pressure.
Thursday, February 27, 2014 at 7:07pm

Chemistry
3.)What is the mass of a bar of aluminum measuring 1.0cm by 1.0cm by 10.0cm Aluminum density: 2.7 g/mL a ml is a cm^3 (nasty of whoever) so Al is 2.7 g/cm^2 you have 10 cm^3 so you have 27 grams which is .027 kilograms
Thursday, February 27, 2014 at 7:04pm

Chemistry
Then they must give you the density of air
Thursday, February 27, 2014 at 7:00pm

Chemistry
2.)What is the volume in liters of a kilogram of ice at 0 degrees Celsius? given 0.9167 g/cm3 at 0 °C which is 1.09 cm^2/g (1.09 cm^3/g)(1 L/1000 cm^3)(1000 g/kg) = 1.09 L/kg by the way : "a pint is a pound the world around" :) (VERY approximate) a pint is about ...
Thursday, February 27, 2014 at 6:59pm

Chemistry
Damon, that's not the math we are using. That is more advanced. Currently, we are using the equations between density, mass, and volume.
Thursday, February 27, 2014 at 6:51pm

Chemistry
number 1 requires the gas law in one way or another at STP a mole of gas occupies 22.4 liters as a check STP is 273 K we are at 293 K I guess we are at one atm, it does not say V = 5 liters P = 1 atm T = 293 R = 0.0821 liter·atm/mol·K PV = n R T n = PV/RT = 1 * 5...
Thursday, February 27, 2014 at 6:47pm

Chemistry
Ice density: 0.9167 g/cm3 at 0 °C Aluminum density: 2.7 g/mL
Thursday, February 27, 2014 at 6:45pm

Chemistry
#1 - no way to know, without some information about the pressure. #2,3 just remember that mass = density * volume Look up the density of ice and aluminum, and you're almost done.
Thursday, February 27, 2014 at 6:40pm

Chemistry
I did have a lot of those questions and I used the method you did. Thanks for the help!!!!!
Thursday, February 27, 2014 at 6:35pm

Chemistry
Same with these: How do you do them? 1.)What is the mass at 20 degrees Celsius of 5 liters of air? 2.)What is the volume in liters of a kilogram of ice at 0 degrees Celsius? 3.)What is the mass of a bar of aluminum measuring 1.0cm by 1.0cm by 10.0cm?
Thursday, February 27, 2014 at 6:34pm

Chemistry
well you can do it in what I think are much more difficult ways Like say I need to go from km to cm well a km is 1000 meters and a meter is 100 cm so a km is 100,000 cm so multiply your 72 km/h by 100,000 to get 7,200,000 cm/h now deal with the hours 1 hour = 60 min and each ...
Thursday, February 27, 2014 at 6:28pm

Chemistry
Use standard enthalpies of formation to determine ΔHorxnfor: 3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g) -133.5 = Delta H Find the change in internal energy for this reactioion.. ???? In KJ
Thursday, February 27, 2014 at 6:27pm

Chemistry
Oh! Ok, thank you! I get it know.
Thursday, February 27, 2014 at 6:23pm

Chemistry
by the way, I use it so much that I remember 3600 s/h but (60 min/h)(60 s/min) min cancels and I have (3600 s/h)
Thursday, February 27, 2014 at 6:22pm

Chemistry
could you go through the steps in a different way maybe? I still don't get it.
Thursday, February 27, 2014 at 6:21pm

Chemistry
if something is the same top and bottom, I call it one. for example 100 cm / 1 meter = 1 in my world, but the units change without changing the value so 72 km /h (1000 m/1km)(100 cm/m)(1h/3600s) km cancels h cancels m cancels and I am left with cm/s now do the calculation 2000...
Thursday, February 27, 2014 at 6:16pm

Chemistry
Same with these: How do you do them? 1.)What is the mass at 20 degrees Celsius of 5 liters of air? 2.)What is the volume in liters of a kilogram of ice at 0 degrees Celsius? 3.)What is the mass of a bar of aluminum measuring 1.0cm by 1.0cm by 10.0cm?
Thursday, February 27, 2014 at 6:12pm

Chemistry
The speed limit on a certain highway is 72km/h. What is the speed in cm/s? Could you go through each step on how to get the answer? Lots of the questions are like this one, but I don't know how to do them.
Thursday, February 27, 2014 at 6:04pm

Chemistry
Predict the standard cell potential and calculate the standard reaction Gibbs free energy for galvanic cells having the following cell reactions: a.)3Zn + 2Bi3+ = 3Zn2+ + 2Bi b.)2H2 + O2 = 2H20 in acidic solution c.)2H2 + O2 = 2H20 in basic solution d.)3Au+ = 2Au + Au3+ I ...
Thursday, February 27, 2014 at 5:52pm

Chemistry
Calculate the standard reaction Gibbs free energy for the following cell reactions: a.)3Cr3+(aq) + Bi(s)= 3Cr2+(aq) + Bi3+(aq) with Ecell=-.61V b.)Mg(s) + 2H20(l)=Mg2+(aq)+H2(g)+2OH-(aq) with Ecell=2.36 V I know the formula. I just need help figuring out n (change in number of...
Thursday, February 27, 2014 at 4:34pm

Chemistry
mols FeCl2 = grams/molar mass Using the coefficients in the balanced equation, convert mols FeCl2 to mols Fe(OH)2. Now convert mols Fe(OH)2 to grams. g = mols x molar mass = ?
Thursday, February 27, 2014 at 2:40pm

Chemistry
If 507 g FeCL2 were used up in the reaction FeCL2 + 2NaOH > Fe(OH)@(s) + 2NaCL, how many grams of Fe(OH)2 would be formed?
Thursday, February 27, 2014 at 1:13pm

chemistry
Use PV = nRT
Thursday, February 27, 2014 at 12:03pm

Chemistry
hi
Thursday, February 27, 2014 at 11:42am

Chemistry
6.9
Thursday, February 27, 2014 at 11:24am

chemistry
what volume would 4.3 moles of hydrogen gas occupy at 45 degrees and 3.22 atm?
Thursday, February 27, 2014 at 10:19am

Chemistry
A 100.0 mL aliquot of 0.100 M weak base B (pKb=5.00) was titrated with 1.00 M HClO4. Find the pH at the following volumes of acid added Va= 0, 1, 5, 9, 9.9, 10, 10.1, and 12mL
Thursday, February 27, 2014 at 8:35am

chemistry
425.243 g oz 26.1111c 0.555556 c 33 1.3794
Thursday, February 27, 2014 at 1:38am

chemistry
he
Thursday, February 27, 2014 at 1:37am

chemistry
A set of bookshelves rests on a hard floor surface on four legs, each having a cross-sectional dimension of 3.9 6.5 cm in contact with the floor. The total mass of the shelves plus the books stacked on them is 260. kg. Calculate the pressure in pascals exerted by the shelf ...
Thursday, February 27, 2014 at 12:05am

Chemistry
i don't know lol
Wednesday, February 26, 2014 at 10:47pm

chemistry
If the solution is 0.52M and it is 0.52% ionized, then the ions are 0.52% of 2.5M; therefore, (H^+) = (A^-) = 0.0052*2.5 = about 0.013M ......HA ==> H^+ + A^- So plug thes numbers into the Ka expression and solve for Ka. (H^+) = 0.013M (A^-) = 0.013M (HA) = 2.5-0.013 = ?
Wednesday, February 26, 2014 at 10:09pm

Chemistry
You're STILL using 0.0821 for R and I distinctly remember saying when you use P in kPa R must be 8.314. To make things a little easier you could have changed to 0.946 L also. P actually is 56.66 but rounding to 56.7 should be ok. n = PV/RT n = 56.7*0.946/(8.314*308) n = ...
Wednesday, February 26, 2014 at 9:58pm

Chemistry help!
2 errors on B 1. should be p1/t1 = p2/t2 2. T must be in kelvin and you used C 3. Ans is about 652. (725/310) = (p2/279) C.wrong formula. v1/t1 = v2/t2 (3.44/310) = v2/210) Ans is approx 2.3 L d.formula is (p1v1/t1) = (p2v2/t2) (725*3.44/310) = p2*16.9/298). Ans is approx 142...
Wednesday, February 26, 2014 at 9:46pm

Chemistry
mols HCl initially = 0.025 x 0.1 = 0.0025 To end up with pH = 3 (0.001M H^+) we want H^+ to be 1E-3. If we work in millimols and let x = mL of 0.1M NaOH, we have then [(25.00 x 0.1M)-(0.1x)/(25+x)] = 1E-3M Solve for x and I obtained approx 24.5 mL of 0.1M NaOH that must be ...
Wednesday, February 26, 2014 at 9:19pm

Chemistry
6.71 X 10^-18
Wednesday, February 26, 2014 at 9:03pm

chemistry
a solution of 2.5 M weak acid is .52% ionized. what is the Ka value of this acid? ive been stuck on this one for a long time and cant figure out where to even start...if someone could walk me through this itd be great! thanks
Wednesday, February 26, 2014 at 8:58pm

Chemistry
p1v1 = p2v2
Wednesday, February 26, 2014 at 8:41pm

Chemistry Titration Lab
When the endpoint is reached in an acid-base titration the apparent relationship between [H3O+] AND [OH-] they are equal.
Wednesday, February 26, 2014 at 8:26pm

chemistry
7,744
Wednesday, February 26, 2014 at 8:08pm

Chemistry
A sample of oxygen gas at 295 kPa takes up 456 L of space at standard temperature (the “T” in STP). What is the new volume when the pressure is lowered to standard pressure (the “P” in STP)?
Wednesday, February 26, 2014 at 8:02pm

Chemistry multiple choice
2.3
Wednesday, February 26, 2014 at 7:59pm

Chemistry multiple choice
2.3
Wednesday, February 26, 2014 at 7:59pm

Chemistry multiple choice
2.3
Wednesday, February 26, 2014 at 7:58pm

Chemistry
ur stupid
Wednesday, February 26, 2014 at 7:45pm

Chemistry
Calculate the volume of .100M NaOH that must be added to reach ph of 3 in the titration of 25.00 mL of .100M HCl
Wednesday, February 26, 2014 at 7:44pm

Chemistry help!
A sample of gas at a temperature of 37.0°C has a pressure of 725 torr and occupies a volume of 3.44 L. a. Use Boyle’s law to calculate the new pressure if the temperature is held constant and the volume is increased to 6.54 L. torr b. Use Gay-Lussac’s law to ...
Wednesday, February 26, 2014 at 6:46pm

Chemistry
8======D
Wednesday, February 26, 2014 at 6:45pm

Chemistry
I used what you said but I'm still getting the wrong answer. I'm sorry I really struggle in chemistry
Wednesday, February 26, 2014 at 6:35pm

Chemistry
630 mL = 0.630 L; right. 20 C is 20+273 = 293K; right. 0.75atm x 0.630L = n*0.08206*293 n = 0.0196 mols. I suspect you just punched in the wrong numbers or hit the wrong button somewhere on your calculator. Also you quit when you had n. Then n = grams/molar mass 0.0196 = g/32 ...
Wednesday, February 26, 2014 at 6:14pm

Chemistry
Knowing the formulas won't do much good if you don't know how to use them. It is important to use the right units. Looking at the last problem for which you posted your work, see if my correction helps you in the others. If post specific questions, show your work, and ...
Wednesday, February 26, 2014 at 6:07pm

Chemistry
Your numbers don't look all that bad except you are using the wrong R. The value of 0.08206 is used with p in atm. When you use kPa R is 8.314. I would have used 0.946 for 1 qt to L (the easy way to do the conversion is to go to Google, type in "1.00 quart to" ...
Wednesday, February 26, 2014 at 6:02pm

Chemistry
a. How many moles of N2 are present in a 1.00 qt flask that has a pressure of 425 torr at a temperature of 35°C? What is the mass in this na2? It would be much simpler to change quart to liters first, then torr to kpa PV=nRT n= PV/RT Temps in Kelvins, V in liters, P in ...
Wednesday, February 26, 2014 at 5:57pm

Chemistry
The percentages just tell you how much Na2CO3 and NaHCO3 you start with. 1 x 0.62 =0.62g Na2CO3. 1 x 0.38 = 0.38g NaHCO3. I will estimate from here but you confirm and use better accuracy. It makes the fractions come out better. mols Na2CO3 = 0.62/106 = 0.00585 mols NaHCO3 = 0...
Wednesday, February 26, 2014 at 5:52pm

Chemistry
I really struggle in chemistry sometimes I know the formulas but I don't know how to put the correct numbers where they need to be .
Wednesday, February 26, 2014 at 5:20pm

Chemistry
630 ml= 1l= 1000ml 0.63 L 20=293.15 k 0.75*0.63=n*0.0821*293.15 =1687.13002
Wednesday, February 26, 2014 at 5:17pm

Chemistry
1L=1.06qt 1.00 / 1.06 = 0.94339623 425 torr = 56.7 kpa 35= 308.15 k 56.7/0.0821*308.15 = 212814.921
Wednesday, February 26, 2014 at 5:07pm

Chemistry
Show your work and let us find the error. A common error is not using kelvin for temperature. Also remember volume must be in L
Wednesday, February 26, 2014 at 5:05pm

Chemistry
use it
Wednesday, February 26, 2014 at 5:03pm

Chemistry
Use it. Are you looking for a hand out? We try to help, we try not to do.
Wednesday, February 26, 2014 at 5:03pm

Chemistry
1. Consider a 1.00g unknown sample that contains 62.0% sodium carbonate and 38.0% sodium bicarbonate, NaHCO3, by mass. When this sample is dissolved in water, how many mL of 0.200M HCl will be required to convert all of the carbonate to bicarbonate? How many mL will be ...
Wednesday, February 26, 2014 at 5:03pm

Chemistry
So do the steps.
Wednesday, February 26, 2014 at 5:02pm

Chemistry
Show your work. Probably you aren't following my instructions OR I goofed somewhere.
Wednesday, February 26, 2014 at 5:02pm

Chemistry
Why don't you show your work and let us find the error? You can play hide and seek with these problems all day long.
Wednesday, February 26, 2014 at 4:59pm

Chemistry
delta T = Kf*m Substitute and solve for m m = mols solute/kg solvent Substitute and solve for mol solute. mols = grams/molar mass. You know grams and mols, solve for molar mass. Then (empirical molar mass)*x = approx molar mass. Solve for x and round to whole number.
Wednesday, February 26, 2014 at 4:57pm

chemistry
I worked this for you yesterday. Go back and find the post.
Wednesday, February 26, 2014 at 4:54pm

Chemistry
1 kg = 1000 g mols NaOH = 1000 g/molar mass = ? Then M = mols/L solution. Solve for L solution.
Wednesday, February 26, 2014 at 4:53pm

Chemistry
HNO3 is 100% ionized.
Wednesday, February 26, 2014 at 4:52pm

Chemistry
All of these problems are similar.
Wednesday, February 26, 2014 at 4:52pm

Chemistry
Look at the KOH problem.
Wednesday, February 26, 2014 at 4:51pm

Chemistry
Look at your KOH problem.
Wednesday, February 26, 2014 at 4:50pm

Chemistry
mols KOH = grams/molar mass M KOH = mols/L solution M (OH^-) = mols KOH since the KIOH is 100% ionized. pOH = -log(OH^-) Then pH + pOH = pKw = 14. You know pKw and pOH, solve for pH.
Wednesday, February 26, 2014 at 4:50pm

Chemistry
pH = pKa + log (In^-)/(HIn) Using pKa and pH of 4.00, you can solve for (In/HIn) Remember the ratio must be at least 10:1 to change color (or 1:10 depending upon how you look at it).
Wednesday, February 26, 2014 at 4:47pm

Chemistry
a. How many moles of N2 are present in a 1.00 qt flask that has a pressure of 425 torr at a temperature of 35°C? What is the mass in this na2? It would be much simpler to change quart to liters first, then torr to kpa PV=nRT n= PV/RT Temps in Kelvins, V in liters, P in kpa...
Wednesday, February 26, 2014 at 4:39pm

Chemistry
150.0 mL flask contains 740. g of N2 at 0°C. What is the pressure in atm. What is the pressure in torr? What is the pressure in psi? I know you have to do: n = grams/molar mass Then PV = nRT R in 0.08206 L.atm/mol.K gives P in atm atm x 760 = p in torr 1 atm = 14.7 psi
Wednesday, February 26, 2014 at 4:37pm

Chemistry
A mixture of gases contains 0.65 mol of N2, 0.70 mol of O2, and 0.90 mol of He. What is the partial pressure of each gas (in atm and in torr) in a 25.0 L cylinder at 340 K? What is total pressure? I know you: Use mols each gas in PV = nRT and solve for p. Then Ptotal = pN2 + ...
Wednesday, February 26, 2014 at 4:36pm

Chemistry
At a temperature of 57oC, a gas inside a 5.30 L metal canister has a pressure of 4000 torr. If the temperature is decreased to 13oC (at constant volume), what is the new pressure of the gas? I know you use the formula (P1/T1) = (P2/T2)
Wednesday, February 26, 2014 at 4:35pm

Chemistry
At a pressure of 2.4 atm a balloon has a volume of 9.8 L. If the pressure is decreased to 0.96 atm (at constant temperature), what is the new volume of the balloon. I know you use the formula P1V1 = P2V2
Wednesday, February 26, 2014 at 4:34pm

Chemistry
A 630. mL flask contains O2 at a pressure of 0.75 atm and a temperature of 20°C. What mass of O2 is present? I know you Use PV = nRT and solve for n = number of mols gas. Then n = grams/molar mass and solve for grams. But I get the wrong answer
Wednesday, February 26, 2014 at 4:33pm

Lab/Chemistry
See you post above under a different screen name. Don't screw things up by using different screen names.
Wednesday, February 26, 2014 at 4:31pm

Chemistry
I know how to set the problem up but when I go to solve I get the wrong answer can you help me please?.
Wednesday, February 26, 2014 at 4:29pm

Chemistry
I know how to set the problem up but when I go to solve I get the wrong answer can you help me please? I really need help
Wednesday, February 26, 2014 at 4:28pm

Chemistry
I know how to set the problem up but when I go to solve I get the wrong answer can you help me please?
Wednesday, February 26, 2014 at 4:26pm

Chemistry please help
Your question is somewhat lengthy and sorta runs in circles; however, I assume the question boils down to why are you using the average. I think the answer is this. You may use individual titrations, calculate EACH run for molarity (or whatever you're calculating) and ...
Wednesday, February 26, 2014 at 4:25pm

Chemistry
a. 2.00E-3 x (5.00/total volume) = ? b. 2.00E-3 x (4.03/total volume) = ?
Wednesday, February 26, 2014 at 4:19pm

Chemistry
A = log 1/T Use A1 = kc1. Substitute A1 and c1 and solve for k. Then A2 = kc2. Substitue A2 and k and solve for c2.
Wednesday, February 26, 2014 at 4:17pm

Chemistry
Use PV = nRT and solve for n = number of mols gas. Then n = grams/molar mass and solve for grams.
Wednesday, February 26, 2014 at 4:15pm

Chemistry
P1V1 = P2V2
Wednesday, February 26, 2014 at 4:14pm

Chemistry
(P1/T1) = (P2/T2)
Wednesday, February 26, 2014 at 4:13pm

Chemistry
Use mols each gas in PV = nRT and solve for p. Then Ptotal = pN2 + pO2 + pHe
Wednesday, February 26, 2014 at 4:12pm

Chemistry
n = grams/molar mass Then PV = nRT R in 0.08206 L.atm/mol.K gives P in atm atm x 760 = p in torr 1 atm = 14.7 psi
Wednesday, February 26, 2014 at 4:09pm

Chemistry
I did that but I keep getting the wrong answer
Wednesday, February 26, 2014 at 3:23pm

Please help with Chemistry?????
5.00 mL of 2.00x10^-3M Fe(NO3)3 is mixed with 4.03 mL of 2.00x10^-3M NaSCN and 1.08 mL of 0.1M HNO3, for a total volume of 10.11 mL. a) What is the initial concentration of the Fe(NO3)3 in the mixed solution? b) What is the initial concentration of the NaSCN in the mixed ...
Wednesday, February 26, 2014 at 3:18pm

Please help with Chemistry?????
A standard solution with a FeSCN2+ concentration of 1.55x10^-4M has a percent transmittance (%T) of 18.8%. Another solution of unknown FeSCN2+ concentration has a percent transmittance of 44.8%. A) Calculate the absorbance (A) of each solution. B) Using the absorbances ...
Wednesday, February 26, 2014 at 3:17pm

Chemistry
It would be much simpler to change quart to liters first, then torr to kpa PV=nRT n= PV/RT Temps in Kelvins, V in liters, P in kpa
Wednesday, February 26, 2014 at 3:15pm

Chemistry
a. How many moles of N2 are present in a 1.00 qt flask that has a pressure of 425 torr at a temperature of 35°C? What is the mass in this na2?
Wednesday, February 26, 2014 at 3:09pm

Chemistry
A 150.0 mL flask contains 740. g of N2 at 0°C. What is the pressure in atm. What is the pressure in torr? What is the pressure in psi?
Wednesday, February 26, 2014 at 3:07pm

Chemistry
EOC Problem 6.046 A mixture of gases contains 0.65 mol of N2, 0.70 mol of O2, and 0.90 mol of He. What is the partial pressure of each gas (in atm and in torr) in a 25.0 L cylinder at 340 K? What is total pressure?
Wednesday, February 26, 2014 at 3:05pm

Chemistry
At a temperature of 57oC, a gas inside a 5.30 L metal canister has a pressure of 4000 torr. If the temperature is decreased to 13oC (at constant volume), what is the new pressure of the gas?
Wednesday, February 26, 2014 at 3:03pm

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