Wednesday
March 12, 2014

# Homework Help: Science: Chemistry

Chemistry
What is the molal concentration of an aqueous calcium chloride solution that freezes at -2.43 degrees C?
Monday, February 3, 2014 at 12:29am

Chemistry II
What is the molal concentration of an aqueous calcium chloride solution that freezes at -2.43 degrees C?
Monday, February 3, 2014 at 12:06am

chemistry
For Au. I would change the dimensions to cm so the volume comes out in cc. volume square based pyramid is V = (1/3)*(b^2)*h = ?cc Look up the density of Au in g/cc and mass Au = density Au x volume from above. Using the conversion from grams to troy oz, convert to troy oz, ...
Sunday, February 2, 2014 at 11:56pm

chemistry
I am too, gold, I think. thanks sooo much for your help
Sunday, February 2, 2014 at 11:43pm

chemistry
yes
Sunday, February 2, 2014 at 11:37pm

chemistry
Do you want gold or rhodium? I'm confused by the problem.
Sunday, February 2, 2014 at 11:33pm

chemistry
In case the vacuum caused the flask to implode the shards of glass would be contained within the tape.
Sunday, February 2, 2014 at 11:31pm

chemistry
I would filter it with a coffee filter. I might try setting the sample aside and see if the silt would settle to the bottom, then decant it.
Sunday, February 2, 2014 at 11:30pm

chemistry
What experiment did you perform?
Sunday, February 2, 2014 at 11:28pm

Chemistry
A very general question which requires a very general answer. The student made an error in weighing or some other part of the experiment. Another possibility is that the "chemistry" of the experiment did not go as expected.
Sunday, February 2, 2014 at 11:28pm

chemistry
Rhodium metal currently costs $1251. per troy ounce (note this is different than a regular ounce! 1 troy ounce = 31.1035g). What would the cost be in dollars to purchase enough gold to form a solid square based pyramid with base dimensions 0.750m by 0.750m and height of 0.500m? Sunday, February 2, 2014 at 11:24pm chemistry mols Al = 9.1080E25 atoms/6.0221E23 = ? mols Al x atomic mass = grams Al Look up the density Al. volume = grams/density. Then volume = pi*(r^2)*h You know pi, r, and volume. Solve for h = length of the wire.Note that I would change r to meters so the answer will be in meters. Sunday, February 2, 2014 at 11:24pm chemistry A sample of aluminum metal containing 9.1080 x 10 to the 25 power atoms is drawn into a cylindrical wire with radius r=0.833 mm. how long must the wire be in meters? Sunday, February 2, 2014 at 11:01pm Science (Chemistry) After submitting the answer, this is what I received as feedback. The system is marking that the amount of moles of precipitate was incorrect, although when I did the problem originally I got the same number that you did. I am just posting this feedback for future reference, ... Sunday, February 2, 2014 at 10:22pm Chemistry 2 Sunday, February 2, 2014 at 10:11pm chemistry the suction filtration flask has been taped with strong black tape. Why was this safety precaution a good idea? Sunday, February 2, 2014 at 10:01pm chemistry A camper obtained a sample of water from a mountain stream for cooking, but the water appeared to be cloudy with silt. What would be the best method of separating the silt from the water? Sunday, February 2, 2014 at 9:59pm chemistry the sand originally white, was a light pink after drying. How could the student improve the color of sand further? Sunday, February 2, 2014 at 9:57pm Chemistry a student used a piece of copper with a mass of 2.85g and obtained 2.95g of copper at the end of the experiment, an apparent recovery of 104$. How could the student account for this result, since the best to expect is 100%.
Sunday, February 2, 2014 at 9:56pm

chemistry
Oh that's true, so you're saying to measure out the amount of methanol needed for a 0.2% solution and the amount of isopropanol needed for a 0.2% solution, adding both to the same 1 mL of water, correct?
Sunday, February 2, 2014 at 9:43pm

Chemistry
We can't draw these things on this website. The best you can do is to google "lewis dot structure CH3CH3C3COH but don't know what this is. You have 5-valent carbons and 2 valent carbon. Can't be.
Sunday, February 2, 2014 at 9:41pm

chemistry
If you interpret the question to be to prepare 0.2% solution methanol and 0.2% solution of isopropanol, and you want to put them in the same container, you add the volume of each required as if the other component were not there. Remember that if you prepare them separately ...
Sunday, February 2, 2014 at 9:38pm

chemistry
I have to prepare a 0.2% water solution of n-propanol and a water solution of methanol and isopropanol at 0.2% that can be in the same container. It didn't specify but I'm pretty sure the solutions are v/v%. For the n-propanol a 0.2% solution should just be 2mg/mL of ...
Sunday, February 2, 2014 at 9:28pm

Analytical chemistry
You want 1000 ppm Cu. You have CuSO4.5H2O; how much of that do you need? That is 1000 x (molar mass CuSO4.5H2O/atomic mass Cu) = approx 3930 g CuSO4.5H2O. That is 3930 grams CuSO4.5H2O/10^6 g solution. You don't want 10^6 g solution, only want 500 g. 500 x (3930/1E6) = ...
Sunday, February 2, 2014 at 9:26pm

Chemistry
Draw the Lewis Structures of the following compounds: CH3CH3CH3COH, H2NCOCH3, HCCCH2OH.
Sunday, February 2, 2014 at 9:26pm

Chemistry Lab
So I did a kinetics lab on the rate of reaction of peroxydisulfate ion with iodide ion. Part 1 was the effect of concentration. One of the questions asked is to calculate the amount of thiosulfate consumed in moles. My results for trial 1 were (Times taken for consumption of 1...
Sunday, February 2, 2014 at 9:25pm

chemistry
458.03
Sunday, February 2, 2014 at 9:04pm

Science (Chemistry)
Pb(NO3)2 + Na2X2O4 ==>Pb(C2O4 + 2NaNO3 millimols Pb(NO3)2 = 35 x 2.82 = approx 98.7 mmols Na2C2O4 = 20 x 0.00221 = approx 0.0442 So 0.0442 mmols PbC2O4 will be formed. (concn) = millimols/mL solution. (Pb^2+) = essentially 98.6/55 = approx 1.8M (NO3^-) = (2*98.7/55) = ? (Na...
Sunday, February 2, 2014 at 8:56pm

Chemistry
0.50M KOH = mols KOH/L solution 0.50 M KOH x 0.050 L = ? mols. Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
Sunday, February 2, 2014 at 8:28pm

Chemistry
%KHCO3 = (0.95/1.50)*100 = ?
Sunday, February 2, 2014 at 8:22pm

Chemistry
Use PV = nRT to convert 2 million liters H2S gas at the conditions listed to mols. Use the coefficients in the balanced equations to convert mols H2S to mols S. That will be mols H2S x (2 mols SO2/2 mols H2S) x (3 mols S/1 mol SO2) = mols S Convert mols S to grams. g = mols S ...
Sunday, February 2, 2014 at 8:20pm

Analytical chemistry
How many grams of solid CuSO4. 5H2O are needed to prepare a 500 ml of a 1000 ppm solution of Cu?
Sunday, February 2, 2014 at 8:18pm

Chemistry
About 50% of U.S. and most Canadian sulfur is produced by the Claus process, in which sulfur is obtained from the H2S(g) that occurs in natural gas deposits or is produced when sulfur is removed from petroleum. The reactions are described by the equations 1)2H2S(g)+3O2(g)=2OS2...
Sunday, February 2, 2014 at 7:45pm

Chemistry
If you total sample mass was 1.50 g, and you determined that 0.95 g were KHCO3, what was the percent mass off the KHCO3 in the sample?
Sunday, February 2, 2014 at 7:40pm

Science (Chemistry)
A student mixes 35.0 mL of 2.82 M Pb(NO3)2(aq) with 20.0 mL of 0.00221 M Na2C2O4(aq). How many moles of PbC2O4(s) precipitate from the resulting solution? What are the values of [Pb2 ], [C2O42–], [NO3–], and [Na ] after the solution has reached equilibrium at 25 °...
Sunday, February 2, 2014 at 7:16pm

Science (Chemistry)
A student mixes 35.0 mL of 2.82 M Pb(NO3)2(aq) with 20.0 mL of 0.00221 M Na2C2O4(aq). How many moles of PbC2O4(s) precipitate from the resulting solution? What are the values of [Pb2 ], [C2O42–], [NO3–], and [Na ] after the solution has reached equilibrium at 25 °...
Sunday, February 2, 2014 at 7:16pm

Chemistry
In a similar experiment, a student needs a 0.50 M KOH solution (MM = 56.11 g/mol). The student only has a 50.00 mL volumetric flask. How much KOH should be added before the flask is filled with water?
Sunday, February 2, 2014 at 7:13pm

Chemistry
millimols = mL x M = ? NOTE: I think 20.0M acetic acid is hard to come by. 18 perhaps but not 20.
Sunday, February 2, 2014 at 6:14pm

Chemistry
20.00 ml of 20.00 M acetic acid is reacted with .1000M NaOh calculate the number of millimoles of acetic acid reacted
Sunday, February 2, 2014 at 6:08pm

Chemistry
Stoichiometry by any other name is stoichiometry. Since all are gases and the conditions apply to everything you can use the shortcut. 750 cc N2O5 x (5 mol O2/2 mols N2O5) = 750 cc (5/2) = ?
Sunday, February 2, 2014 at 5:32pm

Ap Chemistry
Two equations and two unknowns. Solve simultaneously. eqn 1. g NaCl + g KCl = 0.1586g eqn 2. mol AgCl from NaCl + mol AgCl from KCl = mol AgCl total Now put those into math form. Let X = g NaCl and Y = g KCl MM stands for molar mass. --------------------- eqn 1. X + Y = 0.1586...
Sunday, February 2, 2014 at 5:28pm

Chemistry
N2(g) + O2(g) → N2O5(g) What volume of oxygen gas reacts to yield 750.0 cm3 of N2O5? The reaction conditions are 350°C and 2.50 atm pressure. 2N2 + 5 O2 = 2N2O5 I balanced correctly. What is my next step to solve this problem. I am confused and I want to understand ...
Sunday, February 2, 2014 at 5:06pm

chemistry
i am sorry i don't understand! molar mass for what? just for H2 or for 3h2 and N2 also?
Sunday, February 2, 2014 at 5:03pm

Ap Chemistry
a mixture contains only sodium chloride and potassium chloride. a .1586-g sample of the mixture was dissolved in water. it took 22.90 mL of 0.1000 M AgNO3 to completely precipitate all the chloride present. what is the composition(by Mass percent) of the mixture?
Sunday, February 2, 2014 at 4:59pm

Chemistry
you balanced the equaton incorrectly.
Sunday, February 2, 2014 at 4:40pm

Chemistry
You balanced the equation incorrectly. You have 4 O on the left, 10 on the right.
Sunday, February 2, 2014 at 4:40pm

Chemistry
N2(g) + O2(g) → N2O5(g) What volume of oxygen gas reacts to yield 750.0 cm3 of N2O5? The reaction conditions are 350°C and 2.50 atm pressure. I balanced the equation 2N2+2O2 = 2N2O5 BUT I AM NOT GETTING THE CORRECT ANSWER, WHAT AM I DOING WRONG?
Sunday, February 2, 2014 at 4:35pm

Chemistry
N2(g) + O2(g) → N2O5(g) What volume of oxygen gas reacts to yield 750.0 cm3 of N2O5? The reaction conditions are 350°C and 2.50 atm pressure. I balanced the equation 2N2+2O2 = 2N2O5 BUT I AM NOT GETTING THE CORRECT ANSWER, WHAT AM I DOING WRONG?
Sunday, February 2, 2014 at 4:35pm

Chemistry
See your SO2/SO3 question below. Same process.
Sunday, February 2, 2014 at 3:59pm

Chemistry
Balance the equation. 2SO2 + O2 ==> 2SO3 A short cut to stoichiometry problems occurs when all are gases and at the same P and T. The shortcut is that you may use volume and mols interchangeably. 15.0 L O2 x (2 mol SO2/1 mol O2) = ? L SO2.
Sunday, February 2, 2014 at 3:59pm

Chemistry
Oh, okay. I understand now, thank you so much for your help.
Sunday, February 2, 2014 at 3:55pm

Chemistry
N2(g) + O2(g) → N2O5(g) What volume of oxygen gas reacts to yield 750.0 cm3 of N2O5? The reaction conditions are 350°C and 2.50 atm pressure
Sunday, February 2, 2014 at 3:47pm

Chemistry
SO2(g) + O2(g) → SO3(g) What volume of sulfur dioxide gas reacts with 15.0 L of O2? The reaction conditions are 875°C and 1.00 atm pressure
Sunday, February 2, 2014 at 3:46pm

Chemistry
yes. The problem in words works out this way. You have so many mols NH3 at the beginning. You had an excess of HCl which reacts with all of the NH3 and leaves extra HCl in the solution. The first thing you want to do is to find the how much excess HCl is there. You do that by ...
Sunday, February 2, 2014 at 3:45pm

Chemistry
I understand everything except how to calculate the mols NH3? Do the mols of HCL used by ammonia equal the mols of NH3 initially? Also, what is the mols excess that you used to calculate the mols of HCl used by ammonia?
Sunday, February 2, 2014 at 3:32pm

Chemistry? Physics? What??
.
Sunday, February 2, 2014 at 2:36pm

Chemistry
NH3 + HCl ==>NH4Cl Excess HCl + NaOH ==> NaCl + H2O Mols HCl added initially = M x L = 0.1M x 0.050L = ? mols NaOH to neutralize excess HCl = M x L = 0.025M x 0.02150 = ? mols HCl used by ammonia = mols initially - mols excess = ? = mols NH3 initially. M NH3 = mols NH3/L...
Sunday, February 2, 2014 at 2:35pm

Chemistry
25 ml of cloudy ammonia solution is added to a 250 ml Erlenmeyer flask. 50 ml of .1 M HCl is then immediately added to the flask, which reacted with the ammonia in the solution. Next, the solution was titrated with .025 M NaOH to neutralize the excess HCl that was not ...
Sunday, February 2, 2014 at 1:49pm

chemistry
1.10 g/mL x 18.4 mL x (34 g Na2CO3/100 g) = ?g Na2CO3
Sunday, February 2, 2014 at 1:14pm

chemistry
How many grams of Na2CO3 are present in 18.4 mL of a 34.0% Na2CO3 solution. The density of the solution is 1.10 g/mL.
Sunday, February 2, 2014 at 1:05pm

chemistry
I assume a jugful means an excess of N2. mol H2 = grams/molar mass Using the coefficients in the balanced equation, convert mols H2 to mols NH3. Now convert mols NH3 to grams. g = mols NH3 x molar mass NH3.
Sunday, February 2, 2014 at 12:19pm

chemistry
3H2+N2=2NH3 if 2.70 g of H2 reacts with jugful of N ,how many grams of NH3 is formed?
Sunday, February 2, 2014 at 12:08pm

chemistry
Heated to what temperature? How big was the piece of Kimwipe? Is the NaHCO3 going to Na2CO3 or Na2O?
Sunday, February 2, 2014 at 11:50am

chemistry
Again, I don't know how you're determining the NaHCO3. If you're titrating it with HCl I don't think there would be a difference. Although you the use of H2SO4 as a titrant would cause pptn of BaSO4 I think it could be done with H2SO4 also.
Sunday, February 2, 2014 at 11:47am

CHemistry
Sunday, February 2, 2014 at 11:43am

Chemistry
Do this in steps and add each step to find total q. 1. Within a phase the formula is q = mass x specfic heat x (Tfinal-Tinitial). For example to heat 20g liquid water at zero C to 100 C (all in the same phase) q = 20 x specific heat x (100-0) = ? 2. At the phase change (solid ...
Sunday, February 2, 2014 at 11:43am

Chemistry
0.5 m solution = 0.5 mol solute/kg solvent. mol = g/molar mass and molar mass = about 82 g/mol. 0.5 mol = 1/2*82 = about 41 So 41g CH3COONa in 1 kg H2O = total mass of 1041g. You want 0.2 mol CH3COONa so 1041g x (0.2/0.5) = ? mass solution
Sunday, February 2, 2014 at 11:39am

Chemistry
What mass in grams of a 0.500 m(molal) solution of sodium acetate, CH3CO2Na, in water would you use to obtain 0.200mol of sodium acetate?
Sunday, February 2, 2014 at 3:59am

Chemistry
At 1 atm, how much energy is required to heat 35.0 g of H2O(s) at –12.0 °C to H2O(g) at 127.0 °C?
Sunday, February 2, 2014 at 3:08am

CHemistry
At 1 atm, how much energy is required to heat 35.0 g of H2O(s) at –12.0 °C to H2O(g) at 127.0 °C?
Sunday, February 2, 2014 at 3:07am

chemistry
The laboratory tech accidentally mixed NaHCO3 with BaCl2-2H2O instead of KCl when preparing unknown mixture for this experiment. How would this mistake affect the calculated percentage of NaHCO3 in the mixture? Justify answer with an explanation. Is it still possible to ...
Sunday, February 2, 2014 at 1:08am

chemistry
A student dried a wet crucible with a Kimwipe. A piece of Kimwipe was left clinging to the inside wall of the crucible, The student did not see the piece of Kimwipe when adding the NaHCO3-KCl mixture to the crucible. The crucible ans its contents were weighed and subjected to ...
Sunday, February 2, 2014 at 1:05am

Chemistry
You didn't furnish enough information to answer; i.e., I don't know what you're determining. If NaHCO3, then be aware that HCl and NaHCO3 react as follows: NaHCO3 + HCl ==> H2O + CO2 + NaCl./ Therefore, some of the NaHCO3 added in the NaHCO3/KCl mixture will not...
Sunday, February 2, 2014 at 12:53am

Chemistry
A student cleaned a crucible with HCl. After pouring the HCl into the waste container, the crucible was neither rinsed with water or dried before the student added the NaHCO3 and KCl mixture. The crucible contained some residual HCl. How would this experimental error affect ...
Sunday, February 2, 2014 at 12:29am

Course Help meeee
All or just one what? If you enroll in pre-med, curricula differ somewhat on where you enroll and where you hope to get into med school. You will take courses (note plural) in biology, chemistry, math, the usual social science, history, English, etc. At many schools that takes...
Sunday, February 2, 2014 at 12:26am

CHEMISTRY
Assuming Cal = 4 for protein, 4 for carbohydrates and 9 for fat, then 110 Cal-(7*9)-(9*4)-(4x) And your question would make more sense without the {\rm g} mishmash.
Saturday, February 1, 2014 at 10:48pm

chemistry
oh okay, that makes sense & a little obvious haha . Thanks.
Saturday, February 1, 2014 at 10:46pm

chemistry
I assume you have a sequence of measurements of mols/grams/amount vs time in seconds. amount at start - amount at 1 sec = amount consumed. This answer is general I know but so is your question with no data.
Saturday, February 1, 2014 at 10:44pm

chemistry
so we did a chem lab and one of the questions is to tabulate the amount of S2O3 consumed in moles and times (sec) for each run. I'm just not sure how to calculate the amount consumed. Can someone please explain how?
Saturday, February 1, 2014 at 10:40pm

CHEMISTRY
The grams of protein in 1 cup of soup that has 110 Cal{\rm Cal} with 7 g{\rm g} of fat and 9 g{\rm g} of carbohydrate. Express your answer using one significant figure.
Saturday, February 1, 2014 at 8:53pm

chemistry
What's that 0.100? 0.100 L? millimols HF = mL x M = 100 x 0.25 = 25.0 millimols NaF = 100 x 0.500 = 50,0 Add 0.002 = 2 millomils HNO3 .........F^- + H^+ ==> HF I.......50.0...0......25.0 add.............2.......... C........-2....-2......+2 E........48.....0.....27 Then...
Saturday, February 1, 2014 at 8:45pm

chemistry
109 mmHg
Saturday, February 1, 2014 at 7:47pm

chemistry
Calculate the pH of .100 of a buffer solution that is .25 M in HF and .50 M in NaF. What is the change in pH on addition of the following? A. .002 mol of HNO3 B. >004 mol of KOH I calculated the correct pH of the solution but am having trouble calculating A & B. Thanks, Ivy
Saturday, February 1, 2014 at 7:11pm

Chemistry
2C4H10 + 13O2 ==> 8CO2 + 10H2O mols C4H10 = grams/molar mass Using the coefficients in the balanced equation, convert mols C4H10 to mols O2. Then use PV = nRT to solve for V. Note 93.5 kPa = 93.5/101.325 atm. Don't forget to change T to kelvin.
Saturday, February 1, 2014 at 7:07pm

Chemistry
What volume of oxygen at 25 degrees celsius and 93.5 kPa will use up 57.1 g of butane?
Saturday, February 1, 2014 at 6:15pm

chemistry
good
Saturday, February 1, 2014 at 5:04pm

chemistry
The answer when rounded is 40, so I got it! -MC
Saturday, February 1, 2014 at 4:52pm

chemistry
Just need help solving this one, please: The grams of fat in one avocado if it has 405 Calories, 13 g of carbohydrate, and 5 g of protein Express your answer using one significant figure. Thanks -MC
Saturday, February 1, 2014 at 4:47pm

chemistry
For the cola drink: If you're using 4 Cal/g carb, then 140/4 = 35 g carb which I would round to 40 and to 1 s.f. that is 4 x 10^1 or 4E1. I don't know what 40 once means.
Saturday, February 1, 2014 at 4:42pm

Chemistry
alright, thanks lol
Saturday, February 1, 2014 at 4:41pm

chemistry
Are you using the same values I am for grams fat, grams protein, grams carbs? Total Cal = g fat + g carb + g protein. 110 Cal = (7*9) + (9*4) + (4*g carb) g carb = (110-63-36)/4 = 2.75 which is rounded to 3.00 and to 1 s.f. is 3 grams. Of course you know that 110 Calories = ...
Saturday, February 1, 2014 at 4:39pm

chemistry
For this one- The grams of sugar (carbohydrate) in one can of cola if it has 140 Cal and no fat and no protein. Express your answer using one significant figure. Is the answer 40 once rounded to sig figs? Thanks
Saturday, February 1, 2014 at 4:33pm

Chemistry
My physics is quite rusty but I believe that would be V^2 = Vo^2 + 2ax V^2 will be zero at the top since eventually the pull of gravity will stop the balls upward flight. 0 = (40 m/s)^2 + 2*(-9.8)*x Solve for x = distance in meters.
Saturday, February 1, 2014 at 4:32pm

chemistry
I need help solving this: The grams of protein in 1 cup of soup that has 110 Cal with 7 g of fat and 9 g of carbohydrate. Express your answer using one significant figure. Thanks -MC
Saturday, February 1, 2014 at 4:29pm

Chemistry
A) 6.63*10-34/1.675*10-27*0.01*3.00*10^8 =1.32*10^-13m
Saturday, February 1, 2014 at 4:23pm

Chemistry
Thats what it looks like.. but im taking chem. in college and have never had a physics course, im really lost.
Saturday, February 1, 2014 at 4:02pm

Chemistry
Thank you x)
Saturday, February 1, 2014 at 3:54pm

Chemistry
(6.00 oz/serving) x 3 servings/mo = 18.00 oz blue fish per month. (0.341 oz Hg/10^6 oz fish( x 18.00 oz fish = ? oz Hg in 18.00 oz bluefish.
Saturday, February 1, 2014 at 3:50pm

Chemistry
What is the maximum height achieved if a 0.800 kg mass is thrown straight upward with an initial speed of 40.0 m·s–1? Ignore the effect of air resistance.
Saturday, February 1, 2014 at 3:50pm

Chemistry
The FDA recommends that women who are pregnant avoid eating more than three 6.00-oz servings of bluefish per month because of the relatively high mercury levels in that type of fish. If bluefish contains 0.341 ppm of mercury (that is, 0.341 oz of mercury per 1×106 oz of ...
Saturday, February 1, 2014 at 3:37pm

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