Friday
April 18, 2014

Posts by DrBob222


Total # Posts: 41,790

6th grade honor science
organic?

chemistry
What volume is 2.00 LL? Is that 2.00 liters? mass 2.00L gasoline = volume x density = 2.00 L x density gasoline (you must look up the density gasoline). Then volume olive oil = mass/density = mass gasoline from above/density olive oil. Solve for volume olive oil.

science
What above experiment? I have no idea what you're talking about. It must have been some kind of experiment in which a gas was involved.

AP Chemistry
Do this like the NaCl M problem. Post your work if you get stuck.

AP Chemistry
HCl + NaOH ==> NaCl + H2O mols HCl = M x L = 3.2 x 0.4 = 1.28 mols NaOH = M x L = 2 x 0.3 = 0.6 mols NaCl formed = 0.6 M NaCl = mols/L = 0.6/(0.4+0.3) = ?

AP Chemistry
You should be able to do this with the NaOH vs HCl problem. Post your work if you get stuck.

AP Chemistry
All of this type can be worked the same way. 1. Write and balance the equation. NaOH + HCl ==> NaCl + H2O 2. How many mols do you have? mols = M x L = 0.81M x 0.77L = 0.624 3. Since 1 mol NaOH = 1 mol HCl (from the equation), then mols HCl = mols NaOH. 4. Those three steps ...

AP Chemistry
pH = -log (H^+). Substitute and solve for M HCl Then follow the instructions above for HCl vs NaOH problem.

AP Chemistry
Salts are made up of a. a cation other than H ion. b. an anion other than hydroxide.

math
(105 mi/3 hr x) 11 hrs = ?

chemistry
Use (P1V1/T1) = (P2V2/T2) The easy way to do this is to make up a convenient number for P1 and V1 and multiply by 4 to find P2 and V2. Another way is to call P1 = P1, then P2 = 4P1. While V1 = V1 and V2 = 4V1

college chemistry
melt ice + move ice from zero to final T + cool H2O from 8 to final T = 0 (mass ice x heat fusion) + (mass melted ice x specific heat H2O x (Tfinal-Tinitial) + (mass H2O x speicif heat H2O x (Tfinal-Tinitial) = 0 Solve for mass H2O. I obtained 420 g but you should confirm that...

chemistry
See your other post.

Northwestern
http://en.wikipedia.org/wiki/Liquid-propellant_rocket#Propellants Scroll to propellants and read.

science
Actually liquid alcohol has a vapor pressure even at room temperature; however, I think the spirit of the question calls for answer A.

chemistry
It looks balanced to me.

Science
Pentane doesn't have hydrogen bonding as does 1-butanol.

Science
I'm thinking you're guessing. This starts out to be a limiting reagent problem. 2H2 + O2 ==> 2H2O mols hydrogen = grams/molar mass = about 2/2 = about 1. mols oxygen = 16/32 = 0.5 mol. Using the coefficients in the balanced equation, convert mols each to mols produc...

Chemistry
E = hc/wavelength = 6.626E-34*3E8/510E-9 = about 4E-19 J/photon but you need to do it more accurately. 1000 J/s*m^2 x 1.3 c (1 m/100 cm) x (1 m/100 cm) = ?P = power of sun hitting a 1.3 cm^2 area. Then 4E-19 J/photon x #photons = ?P Solve for # photons.

Chemistry
This question isn't worded very well in my opinion but I think you want just the enthalpy for the reaction given. Those are dHrxn = (n*dH products) - (n*dH reactants) dHrxn = (1*MgCl2 + 1*H2O) - (1*MgO + 2*HCl) dHrxn = [1*(-641) + 1*(-286)] - [1*(-602) + 2*(-167)] = ?

Chemistry
79.0 kilobytes = 0.07715 megabytes. 0.07715 mB/s x #s = 13.3 megabytes. Solve for #s and convert to minutes.

Chemistry
2070 BTU/hr x 24 hr/day x 365 d/yr = ?BTU ?BTU x 1.055 kJ/BTU = ? kJ. ? kJ x (1 MJ/1000 kJ) = ? MJ.

chemistry
J = 275 x heat fusion = ?

Average Body Fat
http://en.wikipedia.org/wiki/Body_fat_percentage

incomplete---Chemistry
no data listed.

general chemistry II
density x 1000 mL x %H3PO4 x (1/molar mass) = 15M Solve for density = approximately 1.7 but you need to do it more accurately. mass of 1000 mL = 1.73 x 1000 mL = 1730 g mass H3PO4 = 1730 x 0.85 = 1470g g solvent = 1730g-1470 = 260g m = mols solute/kg solvent/kg solvent = 15/0....

Chemistry
If I multiply 365 x 0.0920 x 37 I obtain 1242.46 J which I would round to 1.24E3. I think you punched in the wrong digits AND didn't round properly.

chemistry
NH4Cl + NaNO2 ==> NaCl + N2 + 2H2O 6.33 mols NH4Cl x (1 mol NaCl/1 mol NH4Cl) = 6.33 mols NaCl formed. Then g = mols x molar mass.

chemistry
Use pi = nRT pi = 20/760 T = 273 + 37 R = 0.08206 Solve for n = number of mols. Then n = grams/molar mass. You have n and grams, solve for molar mass.

chemistry
I would g with milk. But better is to get to the hospital. I suspect the answer is orange juice since that is the most acidic of the substances listed..

Chemistry
I didn't know HClO3 had a Ka.

Chemical Bonds
A metal cation may combine with a negative anion to form an ionic compound; i.e., Na^+ + Cl^- ==>NaCl. Metal cations also may form covalent bonds as with Cu^2+ + 4NH3 ==> Cu(NH3)4 ++

Chemistry
Use the Henderson-Hasselbalch equation for a. pH = pKa + log(base)/(acid) b. millimols acid = 200 x 0.1 = 20 millimols base = 300 x 0.075 = 22.5 millimols HCl added = 20 x 0.4 = 8 Set up an ICE chart. .........lactate + H^+ ==> lactic acid I..........22.5....0........20 add...

chemistry
What you have written is the formula for glycerine and not glycine. Let G = grams glycerine and 455-G = grams H2O ------------------------ n = mols; nG = mols glycerine; nH2O = mols H2O molar mass glycerine = about 92 molar mass H2O = about 18. Then [nG/(nG + nH2O)] = xglyceri...

Science ~ Structures and Properties of Matter
1. C CAN'T be right. Water is a liquid and CO2 is a gas so they dont have the same physical properties and you know they don't have the same chemical properties. 2. see below.

science ~CHECK MY WORK PLEASE~
See your posts above.

Science ~CHECK MY WORK PLEASE~
Increasing the density makes it sink. mass = volume x density or density = mass/volume. Increasing v decreases d.

Science ~CHECK MY WORK PLEASE~
See you other posts. You don't need to post so many under different screen names.

science---1 question
right. hydrogen peroxide.

Physical Science
The 60% goes to do the work the machine is designed to do. The other 40% is lost to do the work and it goes out in the form of heat, light, etc.

chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

chemistry
Use PV = nRT

Chemistry
Use the Clausius-Claypeyron equation and solve for delta Hvap.(You know p at 20 and you know p is 760 mm at 74.1.) Then use CC equation a second time and one of the other values to solve for vapor pressure at 277 K (39F). Use PV = nRT and solve for n. Convert n to grams, conve...

CHEMISTRY URGENT!!!!
You're answer is in meters. Convert to nm.

chemistry
volume = pi*r^2*thickness. density = mass/volume.

Chemistry
tetraaqooxalatoferrate(III)

Chemistry
trioxalatoferrate(III) I'll work on #1

Chemistry
The formula I gave you gives wavelength in meters. The question asks for nanometers. Make the conversion. 1 m = 10^9 nm.

Chemistry
1/wavelength = R(1/4 - 1/9) R = 1.0973732E7 The 1/4 is 1/2^2 The 1/9 is 1/3^2

Chemistry
I'm confused. If the question is 10^-2g that is 0.01g = 10 mg. I think 1 tablet will do it although that isn't 10 mg BUT you don't want to overdose.

Chemistry
==> NH4^+(aq) + Cl^-(aq) + H2O(l)

Chem
Pretty general question. %X = (mass X/mass sample)*100 = ?

chemistry
Those constants usually are quite accessible. If they are not in your text/notes, you can google " table freezing point depression constants"

Chemistry
You must know how many mols ethanol. Assuming 1 mol ethanol, then 713 kJ/molX x # mols X = 1370 kJ

Chemistry
g H2O x 0.888 = 50

Chemistry
You work this in stages. Within a phase it is q = mass x specific heat x (Tfinal-Tinitial). For example, for liquid water at zero C to boiling it will be q = mass H2O x specific heat liquid H2O x (100-0). Then at a phase change (from ice to liquid or from liquid to gas it is q...

chemistry
Set up two equation. They are (1) g NaCl + g KCl = 0.8870g (2) g AgCl from NaCl + g AgCl from KCl = 1.913g If you let X = g NaCl and let Y = g KCl, then equation 1 becomes X+Y = 0.8870 and equation 2 becomes X(MMAgCl/MMNaCl) + Y(MMAgCl/MMKCl) = 1.913 where MM stands for molar ...

chemistry
mass = volume x density plug in volume and density and calculat3e mass of each.

Chemestry
The theoretical number is 3 for K2SO4. Since all of that other information is included you must want the actual factor for this particular solution. 5% K2SO4 = 5g K2SO4/100 g solution which is 5g K2SO4/95 g solvent. mol K2SO4 = 5/molar mass K2SO4 m K2SO4 = mols K2SO4/0.095 kg ...

Chemestry
You don't believe 3? That's the right answer.

Chemistry
1.250/250 = ?

chemistry
q = mass x specific heat x delta T. 176 J = 28.1 x specific heat x 16.3 Solve for specific heat and compare with the table provided.

Chemistry - Posted for Rudy
First, I think you left a squared term off the OH^-. Ca10(PO4)6(OH)2(s) --> 10Ca2+(aq) + 6PO43-(aq) + 2OH-(aq) (Ca^2+) = 10x (PO4^3-) = 6x (OH^-) = 2x Ksp = (Ca^2+)^10(PO4^3-)^6(OH^-)^2 Substituting the x values we have Ksp = (10x)^10(6x)^6(4.3e-6 + 2x)^2 I would make the a...

Chemistry
2C8H18 + 25O2 ==> 16CO2 + 18H2O 17,500 miles/19.2 mpg = ? gallons. ? gallons x 3.785 liters/gallon. ?liters x 1000 = ?mL ?mL x 0.703 g/mL = ? grams grams octane/molar mass octane = mols octane. Using the coefficients in the balanced equation, convert mols Octant to mols CO2...

Chemistry
I suppose that you did everything right (and had a little luck).

chemistry
I don't understand the g g and the mL mL but 2900 mL x 1 g glucose/100 mL = 29 g glucose. I think glucose is about 4 calories/g; therefore, energy = 4 cal/g x 29g = ?

chemistry
(V1/T1) = (V2/T2)

Chemistry
total volume = 100 + 50 + 10 + 75 = 235 mL. In the final solution at mixing and before equilibrium (A) = 0.001M x (50/235) = ?M (B) = 0.002M x (100/235) = ?M (C) = 1M x (10/235) = ?M (D) = 0.0015M x (75/235) = ?M So you know at equilibrium (D) = 0.0006M. Therefore, the reactio...

Chemistry
I would do this. ........HA --> H^+ + A^- I.......x......0.....0 C......-y......y.....y E .....x-y.....y.....y You know y = 6.17E-5 Substitute and solve for x =initial (HA) and let's call that M1. (This will be quadratic you must solve.) Do the same for HA in which y = ...

chemistry
2.0 what? I suggest you repost at the top of the page.

Chemistry
Use PV = nRT to find mols. Then g = molx x molar mass

Chemistry
q = mass sample x Ccal x delta T. Divide by 3 to obtain q/1 g sample, and multiply by molar mass to find q for 1 mol KCN. That will give you q in kJ/mol.

Chem
The mols = M x L = ? You will have M of one of the substances and liters for both. At the end point of the titration mols of each substance is the same.

Chemistry
rate = -delta [N2O5]/delta time rate = (0.218-0.0296)/282 = ? Then rate = k[A]. Calculate k.

AP Chemistry
.........HX | H2O ==> H3O^+ X^- I.......0.001..........0.....0 C........-x...........x......x E......0.001-x........x......x Ka = (H3O^+)(X^-)/(HX) (H3O^+) = 0.001*0.06 (X^-) = 0.001*0.06 (HX) = (0.001-(0.001*0.06)

AP Chemistry
I have the same answer you obtained BUT my best guess is that you have reported too many significant figures. You are allowed only two; therefore, I would round that off to 0.15%. Let me know if that clears up the problem (or doesn't clear up the problem).

AP Chemistry
........HZ + H2O ==> H3O^+ + Z^- I......0.78M.........0........0 C........-x..........x........x E.....0.78-x.........x........x Ka = (H3O^+)(Z^-)/(HZ) Use Ka, plug in E line of ionization above and solve for x = (H3O^+). Then pH = -log(H^3O^+) %ion = [(H3O^+)/0.78]*100 = ?...

AP Chemistry
.....C5H5NH^+ + HOH ==> C5H5N + H3O^+ I.....0.41M...............0.......0 C......-x.................x.......x E.....0.41-x..............x.......x Ka for C4H5NH^+ = Kw/Kb for pyradine = (C5H5N)(H3O^+)/(C5H5NH^+) Plug in Kw/Kb to find Ka, then solve for x = (H3O^+). Then use ...

AP Chemistry
(H^+) for a salt of a weak acid and a weak base = sqrt(KwKa/Kb). Solve for (H^+) and you have your answer.

AP Chemistry
........H2O ==> H^+ + OH^- I......liquid....0.....0 C......liquid....x......x E.....liquid.....x......x So Kw = (H^+)(OH^-) Substitute and solve for H^+ and pH.

what??????chemistry
I think you must have meant 2.29 x (100/2.03) = 112.81g KNO3/100 g H2O which I would round to 113 g solute/100 g H2O

chemistry
Both NaI and FeCl2 boil above 1000 C but FeCl2 is difficult (if not impossible) to recrystallize from H2O; therefore, I would go with NaI.

chemistry
q = mass x heat fusion. q = 150g x 79.8 cal/g = ? calories. Convert to kcal.

chemistry
5.2 x 0.15 = ? L blood at rest. 1 L = 1.06 qts. You convert.

chemistry
mols C4H10 = grams/molar mass Using the coefficients in the balanced equation, convert mols C4H10 to mols H2O. Now convert mols H2O to grams. g = mols H2O x molar mass H2O.

Chemistry
q = mass Cu x specific heat Cu x (Tfinal-Tinitial) = ?

chemical science
2 and 2

chemistry
I don't have my calculator handy but that looks right to me. 250 * about 8 = about 2000 J/mol

Chemistry
2KClO3 ---> 2KCl + 3O2

someones GOTTA help me with this science...!!!
One is shown here. http://www.cotf.edu/ete/modules/msese/earthsysflr/water.html I would go with B also.

chemistry
Why would it be anything but 225 grams?

Chem
mols NH4Cl = 4.30g/molar mass NH4Cl= x. m = mols NH4Cl/kg solvent.

Chemistry
Thanks for showing your work. That makes it MUCH easier to spot the problem. P must be in atmospheres, not torr. Convert torr to atm by 2.643E2/760 = ?

chemistry
Diagram? Balanced equation is 2KClO3 ==> 2KCl + 3O2

Chemistry
Strictly speaking, I think that means 2Br2 but I need the equation to tell for sure. Often that refers to Br. For example, if we are talking about the equation of Cl2 + 2Br- ==> 2Cl^- + Br2 we SHOULD say two equivalents of bromide ion but I often hear two equivalents bromin...

Chemistry
You need two equations and solve them simultaneously. The problem doesn't say which acid is used (and it doesn't need to do that) but I will assume HCl and work accordingly. Any acid can be used as long as you keep the N and M straight. The first equation is g Na2CO3 +...

Chemistry
Let x = amount of 0.3200 N HCl needed. m.e. = # milliequivelents Then m.e. H2SO4 + m.e. HCl = m.e. 0.2299 solution. (100mL*0.1234N) + (XmL*0.3200N) = (100mL + xmL)*0.2299 Solve for X.

Chemistry
2KClO3 ==> 2KCl + 3O2 mols KClO3 = grams/molar mass KClO3 Using the coefficients in the balanced equation, convert mols KClO3 to mols O2. Convert mols O2 to volume using PV = nRT.

Chemistry
The law of conservation (of mass) (or matter) says mass (or matter) can't be created or destroyed. Therefore, if you start with a total of x grams you must end up with a total of x grams. And if you start with 14 N atoms or 26 O atoms you must end up with 14 N atoms and 26...

Chemistry
Your answer is close but not quite there I don't think. It takes energy to break the H-H bond and it takes energy to break the O-O bond. Forming the O-H bond produces energy. The sum of forming 4-OH bonds is greater than breaking 2 H-H bonds and 1 O-O bond; therefore, the ...

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