Saturday
October 1, 2016

Posts by DrBob222

Total # Posts: 53,190

chemistry
C'mon. What is your problem with this? It a definition for K. You need to know the definition and you can do these yourself. Also, you need to use arrows. ==> or --> or >>>.
September 11, 2016

chemistry
K = (H2O)^2/(H2)^2(O2) In increase in P means the reaction will shift to the side with fewer mols. So increase in P shifts to the right; therefore, a decrease must shift to the left. There are two answers for left (A and D). Can you figures with Q is larger or smaller.
September 11, 2016

chemistry
Keq = (Fe^2+aq)(Cl^-aq)^2/(FeCl2). Some may argue that the denominator of FeCl2 should not appear; however, by definition it is 1 and like to put it in.
September 11, 2016

Chemistry
0.326 g = mass FeCl2.xH2O -0.254 g = mass FeCl2 -------------- 0.072 g = mass xH2O mols FeCl2 = grams/molar mass = ? mols H2O = grams/molar mass = ? Now find the ratio of 1 mol FeCl2 to H2O and round to a whole number. That whole number will be x. The easy way to do that is ...
September 11, 2016

Chemistry
delta T = Kf*molality You know delta T and Kf, solve for m. molality = mols/kg solvent. You know m and kg solvent, solve for mols. Then mols = grams/molar mass You know mols and grams, solve for molar mass.
September 11, 2016

Chemistry
All you gave was a number. I can't tell you what you're doing wrong since you didn't show your work. The right answer is in the ball park of 560 g
September 11, 2016

chemistry
mols CaCl2 = grams/molar mass. mols Cl^- = twice that since there are 2 mols Cl^- for every mols CaCl2. Then there are 6.02E23 Cl^- for every mol Cl^-.
September 11, 2016

chemistry
Here is a "balanced" equation. 2C2H2 + 5O2 ==> 4CO2 + 2H2O
September 11, 2016

Chemistry
I2 is diatomic. Zn + I2 ==> ZnI2 Use 1 mol I2 = 1 mol ZnI2. If you wanted mols I ATOMS, then 1 mol ZnI2 = 2 mol I atoms.
September 11, 2016

Science
Without knowing the initial procedure or the updated procedure, no one can help you.
September 10, 2016

Chemistry
Zn + 2HCl ==> H2 + ZnCl2 mols Zn = grams Zn/atomic mass Zn = ? Using the coefficients in the balanced equation, convert mols Zn to mols HCl. That will be mols Zn x 2 = mols HCl. Then M = mols/L. You know M of HCl, mols HCl, solve for L HCl and convert to mL
September 10, 2016

Physical Chemistry
a. [mass Au x specific heat Au x (Tfinal-Tinitial)] + [mass Ag x specific heat Ag x (Tfinal-Tintitial)] = 0 Substitute and solve for Tfinal. b. q = [mass Au x specific heat Au x (Tfinal-Tinitial)] OR q = ([mass Ag x specific heat Ag x (Tfinal-Tinitial)] q is the same for each ...
September 10, 2016

chemistry
I think you are right that OMe is a ortho/para directing group. I think the CO2R is an ester and esters are meta directing.
September 10, 2016

Chemistry
M = mols/L M = 1.5 mols/1.5 L = 1.0 M
September 10, 2016

Chemistry (equilibrium)
Since the dH reaction is +312 kJ, that means the reaction is endothermic so I would write it as C2H6 + heat = C2H2 + 2H2 So if T is decreased, rxn shift to the left. (Rxn uses heat to go to the right; take heat away it moves to the left). Add He at constant volume. If volume ...
September 10, 2016

chemistry help
Emma, you didn't like my answer? http://www.jiskha.com/display.cgi?id=1473523976
September 10, 2016

Chemistry
If it exists I would name it nitrogen trioxide.
September 10, 2016

chemistry
I don't think there is an answer. A is true most of the time but not always. It depends, somewhat, upon how acids and bases are defined. D is a true statement but that isn't neutralization. B and D are true, also, but those aren't neutralization reactions.
September 10, 2016

chemistry
I don't understand how the answer can be D. There is no water in the reaction. What you want to do is to shift the equilibrium to the left (remove the OH^-) and you can do that by adding an acid so I would choose B.
September 10, 2016

chemistry
I would go with B.
September 10, 2016

chemistry
I don't think so. H2 + O2 ==> 2H2O If P increases, it shifts to side with fewer moles of gases. There are 3 mols on the left; two moles on the right so for increase P it shifts to the right. A decrease in P must shift to the left.
September 10, 2016

chemistry
You could save a lot of time by using this: 2H2 + O2 ==> 2H2O. Everyone knows that the number two following H and O are subscripts. We CAN write them as subscripts but no one wants to take the time to do it. 2H2 + O2 ===> 2H2O Here is the rule to follow: An increase in ...
September 10, 2016

chemistry
Equilibrium is reached when the forward reaction rate equals the reverse reaction rate.
September 10, 2016

chemistry
I'm having trouble following the question. Please rephrase, don't omit words, and please no abbreviations; e.g. I have no idea what PP end point is.
September 10, 2016

Biochm I
I agree
September 10, 2016

chemistry
All are right
September 10, 2016

chemistry
EDTA complexes CaCO3. Here is explanation. http://www.austincc.edu/dsackett/CHEM1412/lab/1412exp47.pdf
September 10, 2016

Chemistry
You look at the graph and pick the midpoint (the inflection in the graph). At that point, (HA) = (A^-) and pH = pKa.
September 9, 2016

Chemistry urgent please
Sorry, I know nothing about the Japanese pharmacopeia.
September 9, 2016

Chemistry urgent please
If this is a qual test you need have enough dil HNO3 to make the solution slightly acid. Add dil HNO3 to the solution dropwise until it is acid to litmus paper. The actual amount you need to add will be determined by the amount of NaOH present in the test.
September 9, 2016

Chemistry
P*molar mass = density x RT
September 9, 2016

Science
Are these three question? What do you want? Are these multiple choice?
September 9, 2016

Chemistry(please check my answer)
right
September 9, 2016

chemistry
CH4 + 2O2 ==> CO2 + 2H2O mols CH4 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CH4 to mols CO2, then again convert mols CH4 to mols H2O. Then convert mols CO2 and mols H2O to grams of each. g CO2 = mols CO2 x molar mass CO2 g H2O = ...
September 9, 2016

chem help!
Reactions with dG negative are spontaneous.
September 9, 2016

chem help!
dG = -RTlnK If dG is - then K is + and a +K means products are greater than reactants. Products are in the numerator; reactants in the denominator.
September 9, 2016

Chemistry
No details. Can't answer.
September 9, 2016

Chemistry
Note the correct spelling of Celsius. Probably something is missing. With no volume CO listed you can't give a volume of O2 required. However, with no volume CO listed, you could answer that the required amount of O2 required is 1/2 the volume of CO used.
September 9, 2016

chemistry
I read all of these posts. Almost all are solved with the Henderson-Hasselbalch equation, or some variation of the HH equation. I think all of them are buffer problems. I suggest you pick one of them; e.g. the carbonate/bicarbonate problem, show what you have done or what you ...
September 9, 2016

chem
pH> = basic pH<7 = acid pH=7 = neutral
September 8, 2016

chem
I don't like any of the answers but if I had to pick one I would chose A.
September 8, 2016

chem
I don't agree with you. C and D are smaller numbes than A or B
September 8, 2016

chem
http://www.chem.purdue.edu/gchelp/howtosolveit/Kinetics/IntegratedRateLaws.html
September 8, 2016

chem
http://bouman.chem.georgetown.edu/S02/lect4/lect4.htm
September 8, 2016

chem
https://en.wikipedia.org/wiki/Four-stroke_engine
September 8, 2016

Chemistry
https://en.wikipedia.org/wiki/Oncotic_pressure
September 8, 2016

chemistry
rate = k(NO)(O3) rate = 1.5E7(NO)(O3)
September 8, 2016

chemistry
See your other post. Please use the same screen name.
September 8, 2016

chemistry
I believe you need to read and correct the question. Also let me point out that nacl and h2so4 don't mean anything to me. Find the caps key and use it.
September 8, 2016

Chemistry
Frankly I don't understand your question. You're right. Both Cu(OH)2 and BaSO4 are solids and you have labeled them correctly. According to the solubility rules, a reaction proceeds when ONE of the products is a solid. This doesn't change when BOTH products are ...
September 8, 2016

Chemistry
double post.
September 8, 2016

AP Chemistry
3F2 + Cl2 ==> 2ClF3 mols F2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols F2 to mols ClF3. That will be mols F2 x (2/3) = ? Then convert mols ClF3 to grams. g = mols x molar mass = ? This is the theoretical yield (TY). You know from ...
September 7, 2016

Chemistry
yes
September 7, 2016

Chemistry
I'm having trouble with understanding this problem because Ag2CO3 is more soluble than AgI
September 7, 2016

Chemistry
Too little CO2 means too little NaHCO3.
September 7, 2016

Chemistry
It should be obvious that if some CO2 leaks out the amount of CO2 measured will be less so it will be understated. What is it about this problem you don't understand.
September 7, 2016

Chemistry
I'm sorry but my crystal isn't working tonight. If you told me what you did and what you observed I could help.
September 7, 2016

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

Chemistry(please check my answer)
Doesn't the beta particle have energy which means energy is released?
September 7, 2016

Chemistry(please check my answer)
right
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

Chemistry Help Please!
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

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