Thursday
October 23, 2014

Posts by drbob222


Total # Posts: 44,667

CHEMISTRY
mols O2 = grams/molar mass = ? Use the coefficients in the balanced equation to convert mols O2 to mols Mg.
October 23, 2014

Chemistry
What kind of % is that? % by mass or m/v? I'll assume percent by mass. Convert 5% solution to M. 5.00% w/w means 5 g NaOH/100 g solution. 5g NaOH = how many mols. mols = grams/molar mass = 5/40 = 0.125 mols. What's the volume. mass = volume x density or v = m/d = 100g/...
October 22, 2014

Chemistry
dE = q + w You know q. w is -p(Vfinal-Vinitial) You have 7 mols gas on the left at 22.4 L/mol if this is at STP. You have only 4 mols gas on the right. That should give you Vfinal and Vinitial and work will be in units of L*atm. Multiply that by 101.325 to convert L*atm to J. ...
October 22, 2014

Chemistry
Are you sure this is potassium manganate or should you have written potassium permanganate.
October 22, 2014

Chemistry
Take a 100 g sample which gives you 30.46% N 69.54% O Convert to mols. 30.46/atomic mass N - about 2.2 but you can do it more accurately. 69.54/atomic mass O = about 4.4 Now find the ratio of the two to each other with the smaller number being no less than 1.00. You can see ...
October 22, 2014

Chemistry
Fe + O2 ==> FexOy 6.25g + ? = 8.15g Therefore, the amount of oxygen added must be 8.15-6.25 = 1.90. %Fe = (6.25/8.15)*100 = about 77% but you can (and must) do that more accurately. %O = (1.90/8.15)*100 = about 233%. Do all of these plus all that follows more accurately. ...
October 22, 2014

Chemistry (urgent)
I assume that is magnesium oxalate but I don't know that. Also,I assume you meant potassium manganate and not permanganate. MnO4^2- + C2O4^2- + H^+ ==> H2O + CO2 + Mn^2+ Balance the equation. 100 cc C2O4^- but you don't show the molarity of the oxalate solution.
October 22, 2014

Chemistry
We can't draw diagrams on this forum but if you will google "titration curves" you will get good looking pictures.
October 22, 2014

Chemistry
There is no way to calculate the identity of the limiting reagent because you don't list any values for the concentrations.
October 22, 2014

San Bernardino valley college
Substitute the value of h in the first equation into the second equation as follows: 1/2(5L-3)*L = 34 Now solve for L, then h.
October 22, 2014

San Bernardino valley college
The subject is not San Bernadino valley College. Let L = length and h = height ------------------ h = 5L-3 1/2(hL) = 34 Solve for h and L.
October 22, 2014

Chemistry
Ag(s) + Fe^3+ ==> No reaction.
October 22, 2014

Chemistry 111
2C2H6 + 7O2 ==> 4CO2 + 6H2O mols ethane = grams/molar mass = approx 0.0.57 but you should confirm this and all of the others that follow because I estimate. mols O2 = 107/32 = 3.34 Now convert mols ethane to mols CO2. That's 0.57 x (4 mols CO2/2 mols C2H6) = 0.57 x 2 = ...
October 22, 2014

Chemistry
w = -p(Vfinal-vinitial) w = -(4.0)(5.0-14.0) w = -4.0*-9 = +36 L*atm If you want to convert to J multiply by 101.325.
October 22, 2014

chemistry
So how much of this do you know how to do. You're just throwing work up here.
October 22, 2014

Chemistry
I don't see an apparatus
October 22, 2014

Chemistry
I can do a but not b,c,d. No diagram.
October 22, 2014

Chemistry
See your other post.
October 22, 2014

Chemistry
Where are you stuck? What do you not understand about how to do this?
October 22, 2014

Chemisty
I believe ascorbic acid is a diprotic acid which I will label as H2A. Total mols NaOH used = M x L = approx 0.00353 mols NaOH. The solution contained 1.45E-5 mols ascorbic and that will use 2*1.45E-5 = 2.90E-5 mols NaOH. That leaves 0.003531-2.90E-5 = 0.00350 for mols NaOH to ...
October 22, 2014

Chemisty
You have 0.0350 L x 0.175M = about 0.006125 mols H2SO4. It will take 2x that for mols NaOH
October 22, 2014

Easy chemistry
I think A is the answer although it isn't stated very well. It also acts as a galvanic cell for everything else it runs in the car including starting the engine etc. I didn't choose B because when it is being recharged by the alternator in the car it is acting as an ...
October 22, 2014

Chemistry
See your other post.
October 22, 2014

Biochemistry
HCl = 150 x 0.1 = 15 millimols NaOAc = 300 x 0.1 = 30 millimols. pH = pKa + log (base)/(acid) Substitute and solve for pH
October 22, 2014

Chemistry
If you started with 100 mL and ended with 125 mL, you must have added 25 mL of the 0.1M AgNO3. If the (Ag^+) = (Cl^-) at this point you must have titrated all of the Cl^- and you have a saturated solution of AgCl and none of the Ag2CrO4 has pptd. What's the concn of the Ag...
October 22, 2014

chemistry
I got about half way through the problem and discovered you've made a typo somewhere. I suspect that's supposed to be 2.00 mg and NOT 2.00g. Check your figures and repost.
October 22, 2014

Chemistry
mols NaOH = M x L = ? mols H2SO4 = 2x mols NaOH M H2SO4 = mols H2SO4/L H2SO4
October 22, 2014

chemistry
Assuming you mean Cp = 0.387 J/g*C, then q = mass Cu x specific heat Cu x (Tfinal-Tintial)
October 22, 2014

chemistry
See your post above and please use he same screen name.
October 21, 2014

Chemistry
Use PV = nRT and substitute the conditions for the 5.94 atm. p = 5.94 atm V = 35.0 L R = 0.08206 T = 273.15 + 22.5 = ? Solve for n and convert n to grams. x grams = n x molar mass O2. You started with 387g You want to end up with x grams The difference is what you must vent
October 21, 2014

Chemistry
I don't see any apparatus below.
October 21, 2014

Chemistry
You didn't show anything to the right, probably because you can't post a picture or link. I assume this is the other isomer and that would be -100 .
October 21, 2014

Chemistry
mL1 x M1 = mL2 x M2 165 x 0.976 = mL2 x 6.36 Solve for mL2, place that in a container and add enough water to make 165 mL.
October 21, 2014

Chemistry
q = mass x specific heat x (Tfinal-Tinitial) Remember to change mass H2O to mols H2O if you use sp.h. in J/mol
October 21, 2014

Science!
I suspect the correct answers are as Brainiac suggested and I assume this is a lower level course. I don't want to confuse you and I can't draw the structure on this forum; however, I would like to point out a few things. 1. The Lewis dot structure you drew satisfies ...
October 21, 2014

Chemistry
See your post below. And it works better to use the same screen name.
October 21, 2014

Chemistry
heat lost by warm water + heat gained by cool water = 0 [mass warm water x specific heat water x (Tfinal-Tinitial)] + [mass cool water x specific heat water x (Tfinal-Tinitital)] = 0 Substitute and solve for Tf. Note that with density H2O of 1.00 g/mL that makes mL H2O the ...
October 21, 2014

Chemistry
-133.5 kJ for the reaction. You have 3 mols gas on the left (volume wise if H2O occupies no volume and I suppose we suppose it doesn't) and 1 mol gas on the right. 3 mols gas on the left at STP is 3*22.4 and on the right is 1*22.4L. In the absence of other information I ...
October 21, 2014

Chemistry
1. Is the reaction 133.5 FOR THAT REACTION or per mole NO2? 2. And tht's 133.5 what? kJ/mol or kJ/reaction; i.e., for 3 mols NO2.
October 21, 2014

Chemistry
1. Use q = mass x specific heat x delta T. That explains it all. Reason throught it. If you still need help let me suggest you substitute 0.1 for specific heat along with some number for mass and delta T and solve for T. Then substitute 5 for specific heat and the same numbers...
October 21, 2014

Chemistry
dHrxn = (n*dHf products) - (n*dHf reactants)
October 21, 2014

Chemistry
I think the easy way to do this is to graph it as mv on the y axis and M on the x axis. If you do that you can estimate just on scratch paper, that it is about 2.7 x 10^-3 M for the unknown. If you want to do it without graphing you can try this You have -211.3 mv for 1.00E-3M...
October 21, 2014

??Chemistry
??
October 21, 2014

Chemistry
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants. C2H5OH + 3O2 ==> 2CO2 + 3H2O g ethanol = 4.60 mL x 0.789 = approx 3.6 g BUT you need to this calculation and ALL that follow over to obtain a better answer for each step. ...
October 21, 2014

Science
I'm not sure I get the question. It appears obvious to me that you place a thermometer in each liquid, let it boil, and read the boiling point from the thermometer.
October 21, 2014

Science!
That would be my choice.
October 21, 2014

Chemistry
pH = pKa2 + log (base)/(acid) base is 0.140M Na2HPO4 acid is 0.120 M KH2PO4 Substitute and solve for pH. I prefer to work in millimols (mmols) for the second part of the problem. 100.0 mL x 0.140 = 14.0 mmols base Na2HPO4 100.0 mL x 0.120 = 12.0 mmols acid KH2PO4 added 55.7 mL...
October 21, 2014

Chemistry
Use the HH equation. pH = pK3 + log (50.3*0.103)/(0.170*mL) Solve for mL.
October 21, 2014

CHEM
(P1V1/T1) = (P2V2/T2)
October 21, 2014

chemistry
4 mols Mg x (1 mol O2/2 mol Mg) = 4*1/2 = ?
October 21, 2014

chemistry
See your other post.
October 21, 2014

chemistry
Look up the density. Then volume = mass/density
October 21, 2014

Chemistry
0.025 mols NaOH = 1/2 * 0.025 mols H2C2O4
October 21, 2014

Chemistry
I'm still looking for answers to my earlier response.
October 20, 2014

Easy Chemistry
Take a tip from my last response. What do you know? How would you solve it? What do you not understand?
October 20, 2014

chemistry
2.000L for part a is correct. H2 + Cl2 ==> 2HCl When working with gases remember that you can take a short cut and use L directly as mols IF everything stays at the same T and P. So I do this. ...........H2 + Cl2 ==> 2HCl I.........3.95..1.00....0 C........-1.00.-1.00......
October 20, 2014

chemistry
It's time you started showing some work before posting. Please talk about what you think the answer is and why or in difficult cases what it is you don't understand about the question; i.e.,why you are stuck. For this one go through the following thoughts: 1. The anode...
October 20, 2014

Chem
Your answer is hard to follow but I don't think it's right. q = mass H2O x specific heat H2O x delta T 27,123 kJ = 1 kg x (4.184 kJ/kg*C) x delta T or if you prefer it can be 27,123 J = 1000g x 4.184 J/g*C x delta T. If you want to do the last part first, which is what...
October 20, 2014

Bio- Chemistry
http://www.diffen.com/difference/Animal_Cell_vs_Plant_Cell
October 20, 2014

Chemistry
1. mols NaOH = grams/molar mass Then M = mols/L solution. I suppose you are supposed to take the density of H2O as 1.0 g/mL which makes 150.00g H2O= 150 mL. 2. q = mass H2O x specific heat H2O x delta T 3. delta H rxn = q/2.25 give you per gram. That x molar mass NaOH gives ...
October 20, 2014

biology--not chemistry
http://www.life.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/ProkaryoticvsEukaryotic.htm
October 20, 2014

Chem
1a.You must have punched in the wrong numbers. 10.0*1/17)*46.11 is not 23.11 1b. If you use -46.11 then the sign should stay in the answer. 2. I would buy the second part if you added an equal sign.
October 20, 2014

chemistry
I would choose B
October 20, 2014

Chemistry
I just re-read the problem. Are you using NH4NO3 or NH4NO2?
October 20, 2014

Chemistry
If you will show your work I will find the error. Steps? 1. Write and balance the equation. 2. Find pressure H2O @ 25C and calculate pressure dry N2. 3. Find mols N2 4. Use the equation to convert mols N2 to mols NH4NO3.
October 20, 2014

science-chemistry
See the next post up.
October 20, 2014

Chemistry
See your other post
October 20, 2014

chemistry
Heat lost by KNO3 + heat gained by water = 0 q lost by NH4NO3 is 26.3 kJ x (7.315/80) = approx 2.5 kJ but you need a better answer. Since dH is + you know the reaction is endothermic and the solution will get colder. 2.5 = mass H2O x specific heat H2O x delta T. Solve for ...
October 20, 2014

Chemistry
Some of what sample sticks to what stirring rod and how was it used?
October 20, 2014

Physical Science
0.83 WHAT? Is that supposed to be mass human = 100 kg. Is that 85 C or 85 F q = mass x specific heat x (Tfinal-Tinitial) You know q is 1000 kcal. I would change that to calories. You know mass is 100 kg. I would change that to grams. I have no idea what unit 0.83 is but you ...
October 20, 2014

Physical Science
Q = mass Al x specific heat Al x delta T
October 20, 2014

science
Can't you tell from Ms. Sue's first response. She didn't know your choices but practically laid the answer in your lap.
October 20, 2014

Physical Science
Let's use an example. The specific heat of most metals is about 0.3 J/g*C which means it takes 0.3 J to heat a metal 1 degree C. That means it takes very little heat to make the metal hot. If I stick a match to a piece of metal and stick the metal to your arm, it will burn...
October 20, 2014

Chem
See your previous post.
October 20, 2014

Chemistry
#1. k = 0.693/t1/2 Substitute k in the below equation. ln(No/N) = kt No = 5.80g N = ? K = from above t = 552 days Solve for N For #2, you want 1,000,000/2^n = 1,000 Solve for n. The easy way to do that is to solve for 2^n and then n.
October 20, 2014

chemistry
There are 6.022 atoms in 1 mol atoms and 1 mol atoms Al weigh 26.98 grams.
October 20, 2014

Chemistry
Why don't use use the Nernst equation to calculate if the Ag^+ | e ==> Ag half cell goes up or down and how that will affect the voltage of the cell?
October 20, 2014

Chemistry
Yes, c and d are obviously wrong.
October 20, 2014

Chemistry
You didn't answer my previous response. How much do you know about this? Where are you stuck?
October 20, 2014

Chemistry
AgNO3 + KCl ==> AgCl + KNO3 mols AgNO3 = M x L = ? mols KCl needed = mols AgNO3 because of the coefficients in the balanced equation. mols KCl = grams KCl/molar mass KCl. You know molar mass and mols KCl, solve for grams.
October 20, 2014

Chemistry
And you know what about this?
October 20, 2014

Chem
Of course I don't know the contents of Table 6.2. For 2 mols NH3 the equation is N2 + 3H2 ==> 2NH3 (for 2 mols) dH = -46.11*2 kJ 1/2 N2 + 3/2 H2 ==> NH3 (for 1 mol) dH = -46.11 kJ You should add (g) to each to show the phase. I don't know how you got 0. My tables...
October 20, 2014

Easy Chemistry
The half cells are Mg ==> Mg^2+ + 2e Zn^2+ + 2e ==> Zn Oxidation is the loss of electrons.
October 20, 2014

Easy Chemistry
A galvanic cell is essentially a battery. D is the only one using a battery. Technically, a battery is one or more cells made together as in a car battery. The "batteries" in a flashlight are actually single cells.
October 20, 2014

Chemistry
196 x 0.6 = ?lb water. ? lb H2O x (453.6 g/lb) = ? grams H2O The density of H2O is 1.00 g/mL; convert ? g H2O to mL H2O by volume in mL = grams/density. Then mL/1000 = ?L
October 20, 2014

CHM 300
A = absorbance. Sometimes this is measured as %T and if that is done then A = log(100/%T) Then A = ebc where e is the molar absorptivity, b is the cell length in cm and c is the concn in mols/L. You should have measured a standard somewhere in the experiment. Plug in c for the...
October 20, 2014

chemistry
You placed electrodes in in an aqueous solution of HCl. H2 gas bubbled out at the - electrode (the anode) and Cl2 gas was discharged at the cathode (+ elecrode) 2HCl==> H2 + Cl2 . You must fill in from what you did; I wasn't there and don't know what you did.
October 20, 2014

chemistry
NaOH + HCl ==> NaCl + H2O q = mass H2O x specific heat H2O x (Tfinal-Tinitial) mols H2O formed is M x L = 0.0125 dH = q/0.0125 J/mol
October 20, 2014

chemistry
dHrxn = (n*dHf products) - (n*dHf reactants) dHf = delta H formation. Look this up in your text/notes.
October 20, 2014

Chemistry
I'm assuming you meant 1.0 M and not 1.0m. You need to learn the difference. mols KHP = mass/molar mass = 5/204 = about 0.025 mols NaOH needed = 0.025 M NaOH = mols NaOH/L NaOH M = 1.0; mols = 0.025 and L = mols/M = 0.025/1 = about 0.025 L or about 25 mL.
October 20, 2014

Chemistry
Is that % w/v? I assume so. (Xg solute/g)*100 = % (Xg solute/500)*100 = 7%
October 20, 2014

Chemistry need help
1 nitrate ion, NO3^- 2. AgNO3 test shows either Cl^-, Br^-, or I^- present. Oxidation with Cl2 water and mixing with hexane shows either Br^- or I^-. The hexane solvent is purple if I^- so the anion must be Br^-.
October 20, 2014

Chemistry need help please!!!!
1 and 2 answered above. 3 is CO3^2-, carbonate.
October 20, 2014

chemistry
You haven't posted the solubility of benzoic acid at 50C and without that I can't check your work; however, on the surface 1 kg seems too high to me.
October 19, 2014

Chemistry
1. Determine the limiting reagent which will be either HCl or Ba(OH)2. It looks like HCl but you should confirm that before going further. q = 118 kJ x (g HCl/2*molar mass HCl) 2. Then q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute and solve for Tf.
October 19, 2014

chemistry
The molecular equation is 3AgNO3 + Al ==> Al(NO3)3 + 3Ag The net ionic equation is 3Ag^+ + Al ==> Al^3+ + 3Ag The half reactions are Ag^+ + e==> Ag Al ==> Al^3+ + 3e Oxidation is the loss of electrons; reduction is the gain of electrons.
October 19, 2014

Chemistry
3Cu + 8HNO3 ==> 3Cu(NO3)2 + 2NO + 4H2O mols Cu = grams/molar mass Using the coefficients in the balanced equation, convert mols Cu to mols NO. Now convert mols NO to L at STP. 1 mol NO gas at STP occupies 22.4 L.
October 19, 2014

Chemistry
Tbis is a limiting reagent (LR) problem. Pb(NO3)2 + 2NaCl ==> PCl2 + 2NaNO3 mols Pb(NO3)2 = M x L = ? mols NaCl = M x L = ? Using the coefficients in the balanced equation, convert mols Pb(NO3)2 to mols PbCl2. Do the same and convert mols NaCl to mols PbCl2. It is likely ...
October 19, 2014

AP Chemistry
C5H12 + 8O2 ==> 5CO2 + 6H2O dHrxn = (n*dHf products) - (n*dHf reactants). Look up the heat formation of the products and reactants, plug into the above and solve for dHrxn.
October 19, 2014

Chemistry
Could it become a vapor? Have bubbles in the liquid cell? Note the correct spelling of celsius.
October 19, 2014

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