Wednesday
September 17, 2014

Posts by DrBob222


Total # Posts: 43,841

chemistry
M = mols/L = 0.1 mol/10L = 0.01M Qc = (PCl5)/(PCl3)(Cl2) = 0.01/0.01*0.01 = 100. Since Qc>Kc that means the means too much product and too small reactant so the reaction will move to the left to achieve equilibrium. ..........PCl3(g) + Cl2(g) <==> PCl5(g) I.........0....
September 10, 2014

chemistry
See your post above.
September 10, 2014

chemistry
q = mass air x specific heat air x (Tfinal-Tintial) You know q, mass, Tf and Ti. You will need to look up the specific heat of air. Solve for q (in joules) needed. Then 1 watt = 1 joule/second Here is a site that will convert joules to kW-hr. http://www.rapidtables.com/convert...
September 10, 2014

chemistry
q = mass ethanol x specific heat ethanol x (Tfinal-Tinitial) q is 938 J. mass you get from the density and volume. You must look up the specific heat of ethanol. Solve for Tfinal.
September 10, 2014

Chemistry
To follow up on Bob Pursley's response, you know the Cl2 will be the limiting reagent (unless of course you start with too much P4) but I would think you start with some amount of P4, use stoichiometry to add enough Cl2 to form PCl3 and do a separate calculation to see how...
September 10, 2014

chemistry
I assume the concentrations shown are initial concentrations. ...........N2(g)+ O2(g) <--> 2NO(g) I.........0.025..0.025.......0.0015 C..........+x......+x........-2x E.......0.0025+x..0.025+x....0.0015-2x Kc = (NO)^2/(N2)(O2) Substitute into Kc expression and solve for ...
September 10, 2014

chemistry
With Q>K it means products are too large and reactants too small which means the reaction will move to the product side to achieve equilibrium. You need to show the reaction to know which Kc we are talking about; i.e., the forward or reverse reaction.
September 10, 2014

chemistry
In most cases specific gravity is the same numerical value as density in g/mL. density = mass/volume. You have the mass. When you substitute volume in cc or mL you can calculate density.
September 10, 2014

Physical science
AgCl AgNO3(aq) + KCl(aq) ==> AgCl(s) + KNO3(aq) Ag^+(aq) + Cl^-(aq) ==> AgCl(s)
September 10, 2014

Physical science
precipitation reaction ionization or dissociation cation base
September 10, 2014

Chemistry
a. %w/w = (grams solute/g solution)*100 % = [900,000/(100,000+900,000)] x 100 = ? b. M = mols solution/L solution. mols solute = grams/molar mass = ? L solution = 100 Solve c. m = mols solution/kg solvent m = mols solute same as for part b. kg solvent you don't know and ...
September 10, 2014

chemistry
The easy to do this is to determine the molarity of the concentration HCl. That's 1.20 g/mL x 1000 x 0.37 x (1 mol/36.5g) = approx 12 M but you should be more accurate than that. Then use c1v1 = c2v2 12*v1 = 0.25*100 Solve for v1. That will give you the amount of concd HCl...
September 10, 2014

Algebra!!!! HELP
V = k/t^2
September 10, 2014

Physical science
CaCO3 is insoluble. All of the others are soluble.
September 10, 2014

heat change
q = mass Au x specific heat Au x delta T. Solve for delta T.
September 10, 2014

chemistry
This may be a dimensional analysis problem but you don't have enough information to do a dimensional analysis. kg fuel = 0.803 kg/L x L fuel = ? kg. [That part is dimensional analysis. Note that L in the denominator of kg/L cancels with L in the numerator to leave kg.] But...
September 9, 2014

Chemistry
% anything actually is parts per hundred; i.e., how many somethings you have in 100 total. If we had 6 toys and 3 were wagons. we would have 50% wagons. That is % wagons = (# wagons/total toys)*100 = 50%. Or if there are 75 people in a room and 25 of them are men and 50 are ...
September 9, 2014

Chemistry
That shows a tetrahedral structure; therefore, it must be sp3 if you meant Co and not CO
September 9, 2014

Chemistry
Do you mean [CoCl4]^2- https://www.google.com/search?q=[COCl4[^2-&client=firefox-a&hs=ryD&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=IqsPVLOsIoPPggSSyYCwCA&ved=0CCcQsAQ&biw=1007&bih=601
September 9, 2014

Math Problem (please help)
e^0 = 1
September 9, 2014

Chm Help Please!!!
m = molality = mols/kg solvent. You know mols and kg solvent, solve for m Then substitute m into the below equation. delta T = Kb*m Solve for delta T and add to the normal boiling point to find the new boiling point.
September 9, 2014

Organic CHM Lab
Look up the boiling points of n-hexane, benzene and toluene. It should be easier to separate the two with the greater boiling point difference.
September 9, 2014

Organic CHM Lab
Scroll down to flooding and read about that.
September 9, 2014

chemistry
Pethyl ether = Xethyl ether*P<aup>oethylether 380 = X*400 Solve for X
September 9, 2014

chemistry
You must not have copied all of the problem. How far is the jet going?
September 9, 2014

chemistry
How many mols Al(NO3)2 do you have? That's 5.6g/molar mass Al(NO3)3 = ? Then there are 9 mols O (not O2) for every 1 mol Al(NO3)3; therefore, mols Al(NO3)3 x 9 = mols O (not O2). Finally mols O x 16 = grams O.
September 9, 2014

science
mass = volume x density
September 9, 2014

I dont understand this
A. Does the dog have brown fur or does the bone have brown fur?
September 9, 2014

Chemistry, HELP!!
zinc(S) + hydrochloric acid(aq) ==> zinc chloride(aq) + hydrogen(g) Zn(s) + HCl(aq) ==> ZnCl2(aq) + H2(g) Then balance. Zn(s) + 2HCl(aq) ==> ZnCl2(aq) + H2(g)
September 9, 2014

math problem solving
Is it 16?
September 9, 2014

Hard math 7th grade
42 – 2(3 • 5 + 1) = 42 - 2(16) = 42-32 = ?
September 9, 2014

Physical Science
I found this on the net. https://answers.yahoo.com/question/index?qid=20080817023758AAmRgMo
September 9, 2014

chem
CH3COOH + NaOH ==> CH3COONa + H2O mols KOH = M x L = ? mols CH3COOH = mol KOH from the coefficients in the balanced equation. M CH3COOH = mols CH3COOH/L CH3COOH
September 9, 2014

chemistry
You're looking for what we called in much earlier days the chemical factor. It is taught less and less theses days but is very useful. 2Mg/Mg2P2O7 3UO2/U3O6 (NOTE: I assume U3O6 is a made up part of the problem. I would have written it as UO2 but then there is no ...
September 9, 2014

chemistry
BaCl2 + 2KIO3 ==> Ba(IO3)2 + 2KCl millimols BaCl2 = M x mL = 1.4 mmols KIO3 = 3 The is a limiting regent (LR) and solubility product problem rolled into one. First, what is the LR? 1.4 mmols BaCl2 will form 1.4 mmols Ba(IO3)2 if we have all of the KIO3 needed. 3 mmols KIO3 ...
September 9, 2014

chemistry
KBrO3 is a salt soluble in water that ionizes 100%; ie., ..........KBrO3==> K^+ + BrO3 I.........0.01.....0......0 C........-0.01....0.01....0.01 E..........0......0.01....0.01 .........AgBrO3 --> Ag^+ + BrO3^- I........solid......0......0.01 C........solid......x..........
September 9, 2014

biology - - -chemistry
This is chemistry?
September 9, 2014

chemistry
MgCO3(s) → MgO(s) + CO2(g) So the loss in mass is due to the evolved CO2. mass CO2 = 21.8603 - 18.7358 = ? Convert mass CO2 into mass MgCO3 this way. mass MgCO3 = mass CO2 x (molar mass MgCO3/molar mass CO2) = ?
September 9, 2014

Chemistry
a. mols KMnO4 = M x L = about 0.00054 but you need to do that more accurately. Thjat's just an estimate. b. 5Fe^2+ + MnO4^- ==> 5Fe^3+ + Mn^2+ Note that I balanced only the redox part to save a little time but that's all we really need to balance. So mols Fe^2+ must...
September 8, 2014

Chemistry
Ca(OH)2 + SO2 ----> CaSO3 + H2O mols SO2 = 1000/molar mass SO2 = approx 15.6 but you need to confirm that as well as all of the other numbers I do becuase I estimate some of them. Convert to mols Ca(OH)2 and 15.6 mols SO2 x (1 mol Ca(OH)2/1 mol SO2) = 15.7. Grams Ca(OH)2 = ...
September 8, 2014

science
distance = rate x time 30 m = rate x 20 min Solve for rate = 30 m/20 min = 1.5 m/min Now redo d = rt and plug in 1.5 for rate and 60 min for time and solve for d. You can do it with ratio/proportion, also (30 m/20 min) = (x m/60 m) x = ?
September 8, 2014

chemistry
q = mass x specific heat x (Tfinal-Tinitial) Substitute into the equation and solve for Tfinal.
September 8, 2014

Science
http://www.answers.com/Q/Can_one_organism_be_a_consumer_an_omnivore_a_predator_and_prey
September 8, 2014

math
If 5/7 are girls then 2/7 must be boys. Therefore, ......
September 8, 2014

Chemistry help
What trouble are you having doing these? or show your work and I'll check them.
September 8, 2014

please help
Then how are we to tell you which equation is correct?
September 8, 2014

Math - Urgent
5/6 = 15/18 2/9 = ?
September 8, 2014

algebra
4y^2 + 2y -(7y^2 - 3y) ----------- When subtracting, change the sign of the subtrahend and add algebraically. Therefore, this becomes 4y^2 + 2y -7y^2 + 3y ----------- -3y^2 + 5y
September 8, 2014

MATH
Reread your question and tell me what numbers you're talking about.
September 8, 2014

Science
It rotates on its axis once per day (that makes day and night). The earth rotates around the sun once in a year.
September 8, 2014

Physical Science 8th grade
Less dense objects float on more dense objects. For example, a piece of wood floats on water because the water is more dense than wood. Likewise, a balloon filled with He will float in air because air is more dense than He.
September 8, 2014

SCIENCE
You must first find the volume of the flask. Do that with the water. 121.6 g = mass flask + water - 46.8 g = mass flask empty ---------- 74.8 = mass water. density of water is 1.00 g/mL; therefore, m = volume x density 74.8 = volume x 1.00 g/mL volume = 74.8 mL. Then find mass...
September 8, 2014

Science!
I think you're right with D. Suspension, bed load and material in solution are part of stream load. I think D has nothing to do with stream load.
September 8, 2014

chemistry
A radius of 215 pm = diameter of 430 pm and that is 430E-12m. The distance to be covered is 4.47mm or 4.47E-3m. So 430E-12m x #atoms = 4.47E-3 m Solve for # atoms.
September 8, 2014

Chemistry
I would do this. ln (k2/k1) = Ea/RT You know k2 is 1E6k1 and you know Ea for A, solve for Ea for B in which k1 is the rate constant for reaction A and k2 is the constant for reaction B. If products are more stable than reactants then reactions A and B are exothermic and Ea ...
September 8, 2014

Chemistry
dG = -RTlnK
September 8, 2014

science
I can't help with a fourth scenario until I know what the first three are.
September 8, 2014

chemistry
PV = nRT You have P, n, R and T (change to kelvin). Solve for V in liters.
September 8, 2014

Chemistry
physical and physical Adding water to salt and gravel just dissolves the salt. However, the salt is still salt and the gravel still gravel so no reaction took place. Same thing with CO2. Water freezes at zero C and boils at 100 C BUT whether it is in the form of solid ice, ...
September 8, 2014

Chemistry 2
If you start with 0.762M NOBr then NO will be 0.762 x 0.651 = about 0.496M and Br will be 1/2 that. The un-dissociated NOBr will be 0.762 x 0.349 = ? Substitute those values into the Kc expression and solve.
September 8, 2014

Organic Chemistry
Here is a table that lists the pKa for organic and inorganic compounds. http://www.cup.uni-muenchen.de/oc/trauner/files/evans_pKa_table.pdf For example, H2O is 15.7 and HF is 3.17. That means HF is a stronger acid than H2O. I couldn't find NH3 in that list but it is 9.25. ...
September 8, 2014

Biochemistry
I suppose the problem is asking for the anion. If HB is the acid, then the base is B^- and that hydrolyzes in water solution this way. .............B^- + HOH ==> HB + OH^- I..........0.1M............0....0 C...........-x.............x....x E.........0.1-x............x....x ...
September 8, 2014

science
These look ok to me.
September 8, 2014

chemistry
pi = MRT Substitute and solve for M. Then M = mols/L. You know M and L, solve for mols. Then mols = grams/molar mass. You know mols and grams, solve for molar mass.
September 8, 2014

chemistry1411
Use the Clausius-Clapeyron equation. P1 is 630mm Hg and T1 is the unknown. P2 is 760 mm Hg and T2 is 100 C. Remember T must be used in kelvin.
September 8, 2014

chem
1.39 um^3 x (1 mm/1000 um)^3
September 8, 2014

CHEMISTRY
(A) in mols/L or M rate in change in M/s k then is s^-1
September 8, 2014

CHEMISTRY
See your other post.
September 8, 2014

chemistry
rate D is 1/2*d(D)/dT which is 1/2*change in (D)/time. rate E is 1/2*d(E)/dT rate F is d(F)/dT etc. rate = -d(D)/2*dT = -1/2*(0.3) = -0.15 M/s = rate rate = d(H)/dT = 0.15 M/s
September 8, 2014

chemistry
k = 0.693/t1/2 Then substitute k in the following: ln(No/N) = kt No = 100 (I assume this arbitrarily and calculate N based on what I chose for N.) N = 12.8 k from above t = solve for t in years. Note the correct spelling of isotope.
September 8, 2014

chemistry
For mole fraction, X CsBr. mols CsBr = from the problem mols H2O from the problem = grams/molar mass Then X CsBr = mols CsBr/total mols. mass % CsBr is grams CsBr/100 g solution.
September 8, 2014

chemistry
m = mols solute/kg solvent You know m and kg solvent; solve for mols solute. Then mols solute = grams/molar mass You know mols solute and molar mass, solve for grams.
September 8, 2014

chemistry
mass % is grams solute/100 g solution. 12.8% w/w is 12.8g NH3/100 g solution. mass = density x volume. You know 100 g solution and density of the solution; solve for volume of the solution. Convert g NH3 to mols NH3. g/molar mass = mols. Then M = mols/L solution. m = mols ...
September 8, 2014

Biology Help
Enzymes speed up the rate of conversion from reactants to products by lowering the activation energy needed for the reaction to occur.
September 8, 2014

chemistry
There are 453.6 g in 1 lb and 1000 g in 1 kg. There are 12 inches in 1 foot There are 2.54 cm in an inch. There are 100 cm in a m.
September 7, 2014

Chemistry
volume of water = 58.5 mL volume cubes = 2.0 x 2.0 x 2.0 = 8 cc = 8 mL. new volume in BOTH graduated cylinders is 58.5 + 8 = ? No, I didn't err. Both Pb and Al have the same volume so the water levels will be the same when both are submerged.
September 7, 2014

Science
Usually that is applied to a statement when facts are enough to back up the explanation but it makes sense with the information we have. Then we stay that is a tentative explanation because in the future we may find we need to tweak the explanation.
September 7, 2014

science
A hypothesis becomes a theory if the experimental details fit. Then theories become laws with time (sometimes the theory must be tweaked to make it fit new data)
September 7, 2014

chemistry
Most of your questions are about conversions. What is your main problem with these? You need to learn how to do them yourself. If you will explain in detail perhaps we can set you on the right track.
September 7, 2014

chemistry
See your other post.
September 7, 2014

chemistry
1A = 1E-8 cm
September 7, 2014

Chemisty 132
Didn't I do this earlier? (or at least one just like it)
September 7, 2014

chemistry
E = hc/wavelength
September 7, 2014

chemistry
You don't need us to do this for you. Punch in the numbers and that's it.
September 7, 2014

Chemistry
232 amu x (1 g/6.022E23 amu) = ? For d there are 1E-8 cm = 1 A and 1E-9 nm = 1 m
September 7, 2014

chemistry
See your post above.
September 7, 2014

chemistry
volume = (2.04 cm)^3 density = mass/volume
September 7, 2014

questions- - -a level chemistry
1. Is the 0.78 atm the partial pressure to start or after equilibrium is established? 2. What's the new Kp (or Kc) at 350K? I suggest you repost the question at the top of the page and include the information in answer to the questions 1 and 2.
September 7, 2014

Chemistry
q1 = energy released on vapor cooling from 93 C to 78.3 C q1 = mass ethanol x specific heat ethanol vapor x (Tfinal - Tinitial) note: Tf is 78.3 and Ti is 93.0. q2 = energy released on changing from vapor at 78.3 to liquid at 78.3 q2 = mass ethanol x heat vaporization q3 = ...
September 7, 2014

Young Harris College
You do this in steps. q1 = energy needed to heat solid ice from -30 C to solid ice at 0 C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) where Tf is 0 and Ti is -30 C. q2 = heat needed to change the phase at zero C from solid ice to liquid water. q2 = mass ice x heat ...
September 7, 2014

Chemistry
$155 x (1 kWh/0.129) x (1 J/2.78E-7 kWh) = ?
September 7, 2014

chemistry
I would look at B as the incorrect one.
September 7, 2014

Chemisty 132
So this in steps. Within a phase the formula is q = mass x specific heat x (Tfinal-Tinitial). For example, to heat liquid H2O from zero C to 100 C use q = mass x specific heat x (100-0) = ? At a phase change (from ice to liquid at the melting point or from liquid to steam at ...
September 7, 2014

CHM
I have spent a lot of time looking for a site to which I could refer you to for this question but to no avail. So here is my best educated guess and the reasoning. I think volumetric pipets are #1 in accuracy. They require only one measurement reading (when the pipet is full...
September 7, 2014

Chemistry
mols CO2 = 0.0489. Using the coefficients in the balanced equation, convert mols CO2 to mols NaHCO3. Then convert g NaHCO3 to mols; as g = mols x molar mass
September 7, 2014

Chemistry
1.60M x (59.9/208) x [134/(134+111)] = ?
September 7, 2014

Physical Science
What's the density?
September 7, 2014

Chemistry- urgent!
You need to know the rules for significant figures. Here is a good site. Study it carefully. http://www.chemteam.info/SigFigs/SigFigs.html For 15: All multiplication and division. The s.f. rule is the final answer can have as many s.f. as the LOWEST number involved. All of ...
September 7, 2014

analytical chm
I don't know to which methods you refer. You weigh it once, heat, weigh again, and repeat until constant weight.
September 7, 2014

Chemistry (concentrations)
I think Mr. Pursley hit a 6 instead of a 5 and meant 2*12.6 = 25.2 ppt Cl^-.
September 7, 2014

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