Friday
December 2, 2016

# Posts by DrBob222

Total # Posts: 53,730

Chemistry
mols = grams/molar mass = ?
September 7, 2016

@Isabella---Chemistry
If you want an answer it is better to post a new question and not piggy back on another student's question. 1. Convert 9.00 qt to mL. 1 qt = 946 mL. 2. Then mass = volume x density Substitute and solve for mass (n grams). 3. Convert grams to kg.
September 7, 2016

Chemistry
Is that % w/v or w/w. I will assume w/v. 2.5% w/v means 2.5 g/100 mL. You want 400 mL so 2.5 x (400/100) = ?
September 7, 2016

Doesn't the beta particle have energy which means energy is released?
September 7, 2016

Chemistry
I think you are right but I don't think it is 976 C. Perhaps 940.5? I think the other post is in error. You have 520 x 0.481 x (658.5-1000) = 85,416 J available and that is enough to melt all of the solid Al at 658.5 since that takes only 11088 J. The excess heat then ...
September 7, 2016

chemistry
density = mass/volume mass is given. volume = water displaced = 32.1 mL - 26.5 mL = ? mL
September 7, 2016

Chemistry
Suppose we have 5 apples and 5 oranges. The FRACTION of apples is 5/10 = 0.5. To change to percent, it's the fraction x 100 so 0.5 x 100 = 50%. The 100 ADDS the percent sign. % = [(exp-accepted)/acceted]*100. If you want to remove the 100, then the % answer changes to the ...
September 7, 2016

chemistry
coulombs = amperes x seconds C = 3A x 7 min x 60 sec/min = ? 96,485 coulombs will deposit 107.9 g Ag. So 107.9 g Ag x (? C/96,500 C) = ?
September 7, 2016

chem
I would convert density of 1.00 g/mL to lbs/cu ft. I believe that is 62.5 lb/s cubit feet. Convert 208,000 gallons to cubic ft. There are 231 cu ft in a gallon. mass = volume x density. You know volume in cu ft, you know density in lb/cu ft, solve for mass in lbs. Then convert...
September 7, 2016

AP Chem
You end up with 25.4 g Fe2O3. 25.4g Fe2O3 x (2*atomic mass Fe/molar mass Fe2O3) = mass Fe. Piecemeal it's done this way. mols Fe = 25.4 g/molar mass Fe2O3. Since there are 2 mols Fe for every mole Fe2O3, then mols Fe = twice mols Fe2O3. Then g Fe = mols Fe x atomic mass Fe.
September 7, 2016

chemistry
mass H2O = 65.264-36.765 = ? Look up the density of water at 24.8 C. Then mass = volume x density. You know mass and density, substitute and solve for volume.
September 6, 2016

Chemistry
Mass # 10 means protons + neutrons = 10. If it has 7 neutrons, then protons must be 10-7= 3. Atomic number 3 must be Li. So # electrons in the neutral element must be 3. If the element has just two electrons then the charge of the ion must be +1 so the symbol is Li^1+.
September 6, 2016

Chemistry
......MgF2 ==> Mg + F2 ..............1.65..2.57 Therefore, MgF2 must have started at 1.65 + 2.57 = 4.22 kg. Second sample produced 1.33 kg Mg. F2 produced = 2/57 x (1.33/1.65) = ? kg. Convert to grams.
September 6, 2016

Chemistry
The first term you have written is correct; the second and third are not. The first term correctly identifies the energy needed to raise T of 500 g H2O from 20 to 26.2. Your third term should be the steam at 100 C condenses to liquid water at 100 C and helps heat the water to ...
September 6, 2016

Chemistry
You not only imply that it is at the melting point, the sentence states that. So you have solid Al floating in liquid Al at 658.5 C
September 6, 2016

Chemistry - Enthalpy
http://www.jiskha.com/display.cgi?id=1473202007
September 6, 2016

Chemistry
I believe they may be talking about g/cc and kg/m^3 1.5 g/cc and 1.5 kg/m^ are the same.
September 6, 2016

P-Chem
31.7 is ok but are sure that's kg/mol. The density is given in g/L. Besides, a molar mass of 31,700 for a gas seems unreasonably high to me.
September 6, 2016

chemistry
This may be the long way around but here is what I would do. I would determine the M of each solution. 1.68 x 1000 x 0.75 x (1/98) = approx 13 M but you need a more exact number. 1.834 x 1000 x 0.97 x (1/98) = approx 18 M First, how much do you want to prepare. Let's say ...
September 6, 2016

Biochem
pKa Tris is 8.06. You want 0.1 L x 1M = 0.1 mol Tris. I would add 0.2 mol TRIS (grams = mols x molar mass). Add about 50 mL water to the beaker, insert electrodes of a pH meter, add HCl until the pH reads 7.8, transfer to a 100 mL volumetric flask, add water to the mark, mix ...
September 6, 2016

Chemistry
Check your arithmetic. I It looks like you have the right digits (close anyway) but off by a factor of 10. You don't show what you're using for delta H vap or delta H fusion. I used 18 g for a mole of H2O, 334J for delta H fusion and 2257J for heat vap and 4.18 for ...
September 5, 2016

Chemistry
Post your work for each step and I'll check it.
September 5, 2016

Chemistry
Let's see if you can do this yourself. heat at phase change is q = mass x heat vaporization at boiling point or q = mass x heat fusion at freezing point. Between phases it is q = mass x specific heat x (Tfinal-Tinitial). Now you have steam at 155 so it must go "within...
September 5, 2016

Chem
This forum doesn't allow us to draw structures (Lewis or otherwise). You might try to google it.
September 5, 2016

Chem Help - Thank you!
Three questions with no input from you. #1: C2H4 has a double bond so it must be planar. N2H4 has no double bond. 2. http://lessons.chemistnate.com/questions-answered/lewis-structures-and-vsepr-shapes-of-icl2-and-icl2-ions 3.https://www.youtube.com/watch?v=5Dy8XYmFaiU
September 5, 2016

Chemistry
Most is ok but that second term I think should be mice*4.18*(5-0). At any rate, I would change the 6.01 kJ/mol to J/g*C = 334 J/g*C Then [mice*334] + [mice*4.18*(5-0)] + [250 x 4.18 x (5-75) = 0 I solved and got close to 206 g ice needed.
September 5, 2016

oops--Chemistry
That mass is 131 g. Bob P is right.
September 5, 2016

Chemistry
density = mass/volume mass = 13.1 g volume you get from the water displaced; i.e., 35 mL-20 ml = ?
September 5, 2016

chem
What excess? Copy the entire problem. H2SO4 + 2KOH ==> K2SO4 + 2H2O
September 5, 2016

P-Chemistry
You have used too many significant figures. You're allowed 3 places only so you should round those to 35 for pN2 and 22.2 for pCO2 mols fractions are OK.
September 5, 2016

P-Chemistry
mols N2 = grams/molar mass = ? mols CO2 = grams/molar mass = ? Use PV = nRT, substitute EACH (mols N2 and mols CO2 separately) and find pressure of each. You can find X two ways. 1. total mols = mols N2+mols CO2. XN2 = mols N2/total mols XCO2 = mols CO2/total mols. 2. Ptotal...
September 5, 2016

Chemistry
That looks ok to me but I would clean it up a bit. 40.00ml x 1.021 =40.84g A 10.00ml x 1.190 =11.9g B 40.84+11.9 = 52.74 = total grams. 52.74g / 50.00 ml = 1.0548 g/ ml I didn't check the arithmetic.
September 5, 2016

To do these you need to know the rules and that will do it. n can have any whole number from 1 --- to infinity. l(ell) has integral values of 0 to n-1; i.e., 0,1,2,3,....n-1 msubl is -ell to +ell as min to max with inters between, including zero. msubs can have -1/2 or +1/2 ...
September 5, 2016

chemistry
C8H16 + 12O2 ==> 8CO2 + 8H2O mols C8H18 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols C8H18 to mols CO2. Then mols CO2 x 22.4 dm^3/mol = ?dm^3 CO2 ii. CnH2n-2 has an empirical mass of 12n + 2n - 2 = 110 14n = 108 n = about 7.7 which ...
September 5, 2016

Chemistry
mass = volume x density You know mass and density, substitute and solve for volume in cc.
September 4, 2016

Analytical Chemistry
NH3 + H2O ==> NH4^+ + OH^- and (NH4)2SO4 ==> 2NH4^+ + SO4^2- If [(NH4)2SO4] = 0.25 then [(NH4)^+] = 0.50 Use Kb = (NH4^+)(OH^-)/(NH3). You know Kb, (NH4)^+ and (NH3). Solve for OH^- You could use the Henderson-Hasselbalch equation, too, if you've had that in your ...
September 4, 2016

Chemistry
Double post.
September 4, 2016

Chemistry
Why not show your work for the two answers you have so we can find the error. That's a lot easier than us working the problem and letting you look for the error. ......NH4Cl(g) --> NH3(g) + HCl(g) I......0.5..........0........0 C......-x...........x........x E.....0.5-x...
September 4, 2016

Chemistry
2NaN3 ==> 2Na + 3N2 Use PV - nRT and solve for n at the conditions listed. Convert mols N2 needed to mols NaN3 needed. Then grams NaN3 = mols NaN3 x molar mass NaN3.
September 3, 2016

Chem
Do this. Convert 1.560E5 square miles to cm^2. 1 square mile = 2.6E10 cm^2. I get approx 4E15 cn^2 but that's a close estimate only for the area of the state of CA. If you think of a square state (the easy way I think to do this) so a square with sides of approx 6.4E7 cm. ...
September 3, 2016

Chemistry
NH3. A Bronsted-Lowry base accepts a proton. NH3 has a lone pair of electrons on the N, a proton (which needs two electrons) sits down there to produce the NH4^+. So NH3 is the base and NH4^+ is the conjugate acid.
September 3, 2016

Chemistry
That [NH4Cl] = [NH3] + [NH4^+] + 6[Co(NH3)6]^2+ is a mass balance equation. You are adding all of the species in which the NH4Cl will be. You multiply that complex by 6 because it contains 6 times the NH3 found in the other species. So you add all of them together to get the ...
September 2, 2016

Organic Chemistry
I agree with John1. Look at CCl4. In CCl4 both C and Cl have zero formal charge; however, each C-Cl bond is polar. The CCl4 MOLECULE is symmetrical; therefore, it is non-polar but that's because each of the C-Cl polar bonds cancel each other because of the symmetry of the ...
September 2, 2016

CHEMISTRY
Joules = mass Ag x specific heat Ag x delta T. You know mass Ag, look up sp. h. Ag, you know J, solve for delta T.
September 2, 2016

Chemistry
mL1 x M1 = mL2 x M2 mL1 x 3M = 250 x 1M Solve for mL1
September 2, 2016

chemistry
You need to know the solubility at various temperatures. Usually these values are available in the form of graphs or tables. If you don't have that information, you add, say 100 g K2Cr2O7 to 100 g H2O at say 25 C, let it dissolve as much as it will, filter, dry and weigh ...
September 2, 2016

Chemistry
J = mass H2O x specific heat H2O x (Tfinal-Tinitial) = ?
September 1, 2016

Chemistry
Did you know there is a difference between 0.010 m and 0.010 M. I will assume you meant 0.010 M. mL1 x M1 = mL2 x M2 100 x 0.01 = mL2 x 1.0 Solve for mL2 needed. Use that amount and make to 100 mL in a volumetric flask, mix thoroughly, stopper.
September 1, 2016

Chemistry
CaCl2 + Na2SO4 ==> CaSO4 + 2NaCl 9 g CaSO4 is how many mols? That's 9/molar mass CaSO4 = approx 0.066 but you need an accurate answer. Then 0.066 mols CaSO4 will require 0.066 mols Na2SO4 and 0.066 mols CaCl2. g CaCl2 = mols x molar mass = ? g Na2SO4 = mols x molar ...
September 1, 2016

Chemistry
The acid has more H, the base has less fewer H. For example, H2C2O4 is the acid; HC2O4^- is the base.
September 1, 2016

Biochem
But does the problem say equimolar. The pKa I looked up is 8.1 and you want pH of 7.8 so that isn't equimolar. Close but not quite.
September 1, 2016

right. You may want to look at the iron question below. I don't think B is right.
September 1, 2016

You're right. I did not read the question right. I missed the word FALSE. Thanks. And Bob P is right as usual.
September 1, 2016

I don't think the answer is B. If zinc is more easily oxidized which makes it a better reducing agent, then wouldn't the answer be D.
September 1, 2016

Chemistry
Oxidation is the loss of electrons. Reduction is the gain or electrons. S is -2 on the left and 0 on right. H is +1 on the left and +1 on right. O is -2 on the left and -2 on right. N is +5 on the left and +2 on right.
August 31, 2016

chemistry
Read the post and clean up the gibberish. And N will be 28 and not 14.
August 31, 2016

Chemistry
mass reactants: 38.21 + 192.83 = 231.04 g. mass products + left over: 190.83 + 40.21 = 231.04 g. Looks to me like mass reacts equals mass product plus the left over so mass is conserved.
August 30, 2016

Chemistry
This is a limiting reagent (LR) problem and you know that because amounts are given for BOTH reactants. In this case, however, the exact amounts are given. Therefore, you may use either water or CaC2 to start. CaC2 + 2H2O ==> Ca(OH)2 + C2H2 mols CaC2 = grams/molar mass = ? ...
August 30, 2016

Science
Those look ok to me.
August 30, 2016

chemistry
You're right. Go to the head of the class.
August 29, 2016

chemistry
You aren't telling me what you think. Do you know how to get percent? That's %Fe = [(mass Fe/mass Fe(NO3)3]*100 = ? Use atomic masses and molar mass for mass. For part b plug the numbers in part b into the equation I gave you for % and turn the crank.
August 29, 2016

Chemistry
a. Since you have a 100 g sample for all three gases, the percent C and H is the same as grams; i.e., ethane: 79.89% C 20.11% H ethylene: 85.63% C 14.37% H third hydrocarbon: 64.580% C 35.420% H Look up the law of constant composition: it says that the amount of an element in ...
August 29, 2016

Chemistry
Convert the room measurements to cm, then volume comes out in cm^3 (or mL). mass = volume in cc(mL) x density (in g/mL) = ? grams
August 29, 2016

Chemistry
1.049 g/mL x 460 mL x (40/100) = ?
August 29, 2016

Chemistry
Thanks, but I don't get it. The problem doesn't say if it's a gas, liquid, or solid so there must be some kind of lead in information available. You MUST know something else about the problem to get 8 out of it.
August 29, 2016

Chemistry
volume of what? You need to type the whole problem and not just part of it.
August 29, 2016

chemistry
BaSO4 has a certain solubility by itself; with Na2SO4 the solubility is decreased due to the common ion effect. The common ion is the sulfate ion. You have two equilibria. ........Na2SO4 ==> 2Na+ + [SO4]^2- I.......0.250.......0......0 C......-0.250.....0.50...0.250 E...
August 29, 2016

Chem
q1 = heat released on steam cooling from 125 C to steam at 100C. q1 = mass steam x specific heat steam x (Tfinal - Tinitial) where Tf is 100 and Ti is 125. q2 = heat released on condensation of steam at 100 C to liquid water at 100 C. q2 = mass steam x heat of condensation. q3...
August 29, 2016

Chemistry
I would convert the dimensions of the pool to cm then find the volume of the pool in cm^3. volume is length x width x depth. Then mass H2O = volume in cc x density in g/cc. Convert mass in grams to kg, then convert to lbs.
August 29, 2016

chemistry
This won't work. The oxalate ion is loss of electrons and I^- is loss of electrons. In redox equations you must have one half equation losing and one half equation gaining. [C2O4]^2- ==> 2CO2 + 2e 2I^- ==> I2 + 2e
August 29, 2016

incomplete--Organic Chemistry
There are no statements.
August 28, 2016

Chemistry
I didn't address the problem because the third gas doesn't add to 100 g so it must have something else besides C and H and makes it a non-hydrocarbon. I suggest you proof the problem and repost.
August 28, 2016

Chemistry
I worked this problem for you earlier today. Find your other post below.
August 28, 2016

correction==Chemistry
I should have said 1.88 is not right. 24.332 is not right either. If you want to show your work I'll find the error for you. You would need over 6000 grams NaCl in 250 cc solution to have a density of over 24.
August 28, 2016

Chemistry
1.99 is not right. 22,342 is not right.
August 28, 2016

Chemistry
density salt water = mass salt water/volume salt water. mass salt water = 243.2 + 12.8 = 256.0 g. volume salt solution = 250.0 density = mass/volume = 256.0/250.0 = 1.02 g/mL
August 28, 2016

Chemistry
C2H4 + 3O2 ==> 2CO2 + 2H2O mols 1.12 L ethylene = 1.12L/22.4L = approx 0.05 but you should confirm that. So what mass KClO3 will produce 0.05 mols O2 gas? 2KClO3 ==> 2KCl + 3O2 0.05 mols O2 x (2 mols KClO3/3 mols O2) = 0.05 x 2/3 = approx 0.03 but you should get an ...
August 28, 2016

Chemistry
Let's call the hydrocarbon CxHy. Then CxHy + 3O2 ==> xCO2 + (y/2)H2O We know, by adding the O atoms, that 1/2 y(from the H2O) + 2x (from the CO2) that 2x + 1/2 y = 6. If we assume x = 1, then y = 8 and C1H8 is not possible. Try x = 2, then you can do the algebra but y...
August 28, 2016

Chemistry
For every mole Al2O3 you have 2 mols Al. There are 6.02E23 atoms in a mol Al and each atom has 3e involved. 2Al^3+ ==> 2Al + 6e
August 28, 2016

Chemistry
I don't believe KMnO4 can oxidize Na2SO4.
August 27, 2016

Chemistry
p₁ v₁ = p₂ v₂ 3.6 * v = 2.7 * (v + 4.9) You are right to here. The next step you failed to multiply every thing inside the parentheses by 2.7. 3.6v = 2.7v + (2.7*4.9) 3.6v = 2.7v + 13.2 3.6v-2.7v = 13.2 0.9v = 13.2 v = 14.66 which rounds to 14.7
August 27, 2016

Chemistry
I don't think this problem has a simple answer. You can estimate an answer only, I think. 6 mols H2O, as Scott writes, is 108 grams and if we assume the density of H2O is 1.00 g/mL, this then is 108 mL or 0.108 L. However, if we add 0.014 mols HCl to that we don't know...
August 27, 2016

Chemistry
1 mole EDTA reacts with 1 mol CaCl2.2H2O. mols EDTA = M x L = 0.0125 x 0.0189 = approx 0.00024 but you need a better answer to that as well all of the steps that follow. They are estimates also. This was in 10 mL aliquot from 200 mL total; therefore 0.00024 x (200/10) = approx...
August 26, 2016

chemistry
Nor do I. I looked at it several times but it doesn't make sense to me.
August 22, 2016

chemistry
You need to indicate your thoughts on these. What do you the answers are and why. For example, this looks straight forward to me; i.e., you just plug in the definition.
August 22, 2016

Chemistry
August 21, 2016

Chemistry
Actually you can pick any number you wish and that will be right. You didn't specify how much KOH is mixed with how much HNO3. ASSUMING that you have equal volumes of the acid and the base, the pH will be 7 since the nitrate ion is not hydrolyzed and neither is the K^+.
August 21, 2016

chemistry
If I wrote the formula from your name of sodium trioxocarbonate, I would write it as Na2O3CO3 and there is no such thing. Carbonate tells you that you want the [CO3]^2-. The trioxo is completely unnecessary. Also you wrote the concn of HCl as 0.2m. I'm sure you meant 0.2M...
August 21, 2016

chemistry
You need to find the caps key and use it. fe isn't anything. CO, Co, co have different meanings. Rust is one of those complicated formulas. If we assume the formula is Fe2O3. mols Fe2O3 = 30/molar mass Fe2O3 = ? Then 2 x that = mols Fe.
August 21, 2016

Mendulo
% w/w = (grams H2SO4/1 g solution)*100. 15 = (grams H2SO4/25)*100 Solve for g H2SO4.
August 21, 2016

Chemistry
delta T = 7.5 i, the van't Hoff factor for KCl is 2. delta T = i*Kf*molality Substitute for delta T, i, and Kf (1.86) and solve for m. Then m = mols/kg solvent. Substitute for m and kg solvent; solve for mols. Then mol = grams KCl/molar mass KCl. You know molar mass and ...
August 21, 2016

chemestry
volume = (4/3)*pi*r^3 in units of m^3 density = mass/volume = ? in kg/m^3 Convert kg to g and m^3 to cm^3 for the other units.
August 20, 2016

chem
What happens to the volume? If there is no volume change there is no work done. If the volume increases, then the system has done work to the outside and work is negative.
August 20, 2016

chem
Is that average velocity, root means squared velocity, other? KE = 1/2 mv^2 and Urms = sqrt (3RT/M)
August 20, 2016

chemistry
Sofie, this makes no sense. It depends upon what you want to know from G. Is it spontaneous, is it non-spontaneous, is it at equilibrium, do you want to know K or Q, etc.
August 20, 2016

chemistry
You really need to find the caps key and use it. CO, Co, co all mean something different. Na2CO3 ==> 2Na^+ + CO^3- 0.2M Na2CO3 gives 0.2M x 2 = 0.4 for (Na^+) and 0.2 x 1 = 0.2M for (CO3)2-
August 20, 2016

chemistry help!!! please!!! DrBob222 I need you!!
http://www.jiskha.com/display.cgi?id=1471635474
August 20, 2016

chemistry help!!! please!!! DrBob222 I need you!!
I answered this for you yesterday. You can go back and find my answer. Here are the instructions although my post yesterday was different than this (but the same answer). Convert 0.45 mol Al to mols C needed. Use the coefficients in the balanced equation for this. Convert mols...
August 20, 2016