# Posts by drbob222

Total # Posts: 54,989

(-5x+1)(2x-1) = 0 Check that. Set each factor to zero and solve for x.

Chemistry
I've answered this once tod+ay. Note it's Zn(NO3)2, NH3, and aqueous NH3. Think about Zn(OH)2 solubility, aqueous NH3 forming NH4^+ and OH^- and [Zn(NH3)^4]^2+

CHEMISTRY
Why not look it up in your text/notes or look on Google.

Chemistry
How many coulombs were used? That's coulombs = amperes x seconds = 0.45 A x 25 min x 60 sec/min = approx 700 but you need a better answer than this estimate. 96,500 coulombs will deposit (atomic mass/2) grams of the divalent metal. So (atomic mass/2) x (700/96,500) = 0.222...

Chemistry
96,485 coulombs of electricity will deposit 63.5/2 or 31.25 g Cu. Coulombs = amperes x seconds. How many coulombs must you have? That's 96,485 x 2.5 g/31.25 g = ? Then ? coulombs = 1.5 x seconds. You know coulombs and amperes. Solve for seconds. Post your work if you get ...

Chemistry
Use the Arrhenius equation.

Chemestry
mass = volume x density

Chemistry 12
Where did the citric acid come from. I assume it's legal to look up the Ka for benzoic acid.

Chemistry
Call the soft drink, since it is monoprotic, HA. Then HA + NaOH ==> NaA + H2O mols NaOH = M x L = 0.0121 x 1.5 = ? mols HA = the same because of the 1:1 ratio in the balanced equation. M HA = mols HA/L HA or M HA = approx 0.7 but yu need a better answer than that estimate. ...

Chemistry

@Jayzon--Science
You must have meant newton and not netwon.

Chemistry
heat lost by Pb + heat gained by water = 0 heat lost by Pb = mass Pb x specific heat Pb x (Tfinal-Tinitial) heat gained by H2O = mass H2O x specific heat H2O x (Tfinal-Tinitial)

Chemistry
mols Fe(NO3)3 = M x L = ? Convert mols Fe(NO3)3 to mols K2C2O4 using the coefficients in the balanced equation. Then grams K2C2O4 = mols x molar mass = ?

Chemistry
yes

Chemistry
Both A and B are correct. Chemical reactions are by mols and not by grams. That chemical reaction is to read 2 mols Al react with 6 mols HCl to produce 2 mols AlCl3 and 3 mols H2 gas.

Chemistry
.......Mg(OH)2 ==> Mg^2+ + 2OH^- I......solid........0.......0 C......solid........x......2x E......solid........x......2x Substitute the E line into the Ksp expression and solve for x = solubility in mols/L. Convert to grams/L.

Chemistry
If it's 10% w/v sucrose and 0.1%w/v phenylalanine w/v, you're close. 10 g sucrose and 0.1 g phenylalanine in enough water to make 100 mL solution.

Chemistry
A. K.E. = hc/w - hf B Yes. C. Yes.

Chemistry
I spent most of my time trying to figure out how all of that could be a compound of Xe until I realized it could NOT be and ion was the mission word/ I'm glad you confirmed that. Do I assume you need an explanation of why it is BaI2? The electron affinity increases from ...

Chemistry
Would you proof your post please. I think a word is missing "of its common .....is". I wonder if the missing word is ion. As posted element X makes no sense; in fact, [Kr]5s2 4d10 5p6 is Xe and that has the lowest electron affinity in its period. I've spent half ...

Chemistry
Draw the Lewis electron dot structure. Single bonds are longer than double bonds are longer than triple bonds. Where resonance structures appear you will have something between single and double bonds; i.e., it will be shorter than a single bond but longer than a double bond.

chemistry
Yes. I forgot to add the exponent. It should be 2.998E8 m/s

chemistry
Yes, it's the wavelength in meters. c = freq x wavelength c = 2.998 m/s freq = 1040000 Hz Solve for wavelength.

typo??--science
I believe I see a typo here for molality. grams H2SO4 = 1100*0.15 = 165 as stated. mols H2SO4 = 0.15*100/98 as stated. grams solution = 1100 g as stated BUT g solvent = 1100-165 = 935g (0.935 kg) so molality = 0.15*1100/0.935 kg solvent = ?

chemistry
Note the correct spelling of phosphorus. a. A mole contains 6.02E23 molecules; therefore, there are 0.5 x 6.02E23 = ? b. Since there are 4 P atoms to 1 P4 molecules, there must be 4 x the number in a. c. You have 0.5 mole P4 molecules; there must be 4*0.5 = ? mols P atoms. d. ...

I disagree
Mass percent = (mass solute/mass solution)*100 = ? mass solute = 2.50 grams mass solution = 250 g solvent + 2.50 g salt = 252.5 g solution. Then % m/m = (2.50/252.5)*100 = 0.99

sjps science
Do you know how to use Google? I googled the word and came up with this. https://en.wikipedia.org/wiki/Plasmodium

Take the first one. mols N = 1/14 = 0.0714 mols O 1/16 = 0.0357 You can see N is twice that of O sot he formula is N2O. Go through the others in the same fashion to see NO, N2O3 ETC.

Thermodynamic.
We don't know what temperature measuring devices you evaluated.

sjps science
Your sentence isn't complete. Which element? What are the conditions?

chemistry
grams Na^+ = mols Na^+ x molar atomic mass Na^+. Then % Na^+ = (g Na^+/100 mL) = ? Carbonate is done similarly.

Biochemistry
Equation 1 is the Henderson-Hasselbalch. pH = pKa + log (base)/(acid) 6.5 = pKa2 + log (Na2HPO4)/(NaH2PO4) Solve for the ratio base/acid. That's equation 1. Equation 2 is (Na2HPO4) + (NaH2PO4)= 0.3 M Solve the two equations simultaneously for (Na2HPO4) and (NaH2PO4). Those...

chemistry
Use the Henderson-Hasselbalch equation. 4.23 = 3.75 + log(base)/(0.35) and solve for (base) = (formate) but before you do any of that you need to determine if that 0.235 is M, m, g/mL or just what. You should be M. Also, I assume that 3.75 is the pKa but you say in the post it...

Chemistry
According to the web the temperature decreases about 10 C (10K) for every km. What I would do is assume a 1 km height increase. P at surface is about 101 kPa. T is about 298. So P at 1 km is about 101-10 = ? and T at 1 km is 298-delta T whatever that is. I think it's about...

forensic science
or He.

Inorganic Chemistry
In hot water the Mg reacts to form Mg(OH)2 and H2 gas. In strong basic environments ammonium salts decompose to NH3. I don't think Mg(OH)2 is strong enough to cause complete decomposition of (NH4)2SO4 but probably some odor of NH3 could be detected if the reaction is ...

Inorganic Chemistry
In cold water I don't think anything would happen.

Chemistry-Ideal gases

Chemistry
Cl^- is such a weak base that it does not hydrolyze. Think NaCl in aqueous solution. Neither Na^+ nor Cl^- hydrolyzes so NaCl solutions are neutral. That's unlike NH4Cl where the NH4^+ hydrolyzes (Cl^- does not) to make an acidic solution or sodium acetate (NaAc) where the...

Chemistry
My gut feeling is the acetic acid is more acidic but I couldn't prove that.

Chemistry
I've been in this business for 75 years and I've never heard of the molar mass of a tablet. Do you have any other information or an answer? The tablet has a filler of 1.35-0.550-0.110 = 0.690 g but nothing else about it's identity.

Chemistry
How did you get 61?

Chemistry
61 x 4 = 244.

Chemistry
Look for Ka (ionization constant) for HCl, HBr, etc. If it isn't listed it is a strong acid.

Chemistry
Look at the periodic table. Zn is in group 12 (or II), Al in 13 (or III), S in 16 (or VI), Na in 1(or I), N in at(or V). For numbers <10, I, II, III, etc. that's the possible valence. For numbers >10, it's the second number (12, 13, etc). So your answer is >&...

Chemistry

Chemistry
We help but usually we don't do all the work. Here is how you do it. I wonder if you made a typo. HCl, if 38%, I usually see quoted as 1.19 g/mL for density and not 1.10 g/mL. 1.10 g/mL x 1000 mL x 0.38 = grams HCl. Then mols HCl = grams/molar mass Then M = mols/L. For ...

Thanks Reiny.

nb&p_____ 20|7. Make the division set up; I'm sure you know how to do it but it's tough to do on this forum. The 7 is 7. 20 won't go into 7 so you add a 0 to make it 7.0. A decimal point above the line goes above the decimal inside the division set up. Then 20 goes...

Clinical Calculations
I think this man needs to lose some weight. 260 pounds? Yikes.

Chemistry
mass hydrate before heat = 2.545 g mass hydrate after heat = 2.545 x 0.6385 = 1.625 g = mass CuSO4 mass H2O = 2.545-1.625 = 0.9200 g mols H2O = 0.9200/18 = 0.0511 mols CuSO4 = 1.625/159.6 = 0.01 Convert to integers and round to whole numbers for find answer to b. That will ...

Chemistry
%N/%O = 7/16 but 7/16 is the same as 14/32 and that means the empirical formula is NO2. vapor density = 46 = mm gas/mm H2 = mmgas/2 so mm gas = 92 (where mm = molar mass) empirical formula x some # = molecular formula = 96 so the unit # must be 2. (NO2)2 or N2O4 must be the ...

chem
CuClx + Al ==> Cu +_ AlClx (not balanced) mass CuClx = 1.362 -mass Cu = 0.635 ------------------ mass Cl = 0.727 mols Cu = 0.635/63.5 = about 0.01 mols Cl = 0.727/35.5 = about 0.02 Find the ratio of Cu to Cl and write as the empirical formula. If you don't see that ...

Science
100.0/10.3 = ? 3 sig figures allowed.

forensic science

Chemistry
c. lambdfa = h/mv = 1.09 nm b. The threshold is 5.5E15 Hz c = freq x wavelength gives me about 54 nm.

chemistry
This may be the most oddly stated dilution problem I've ever seen. Are you having trouble with the math? (1/100) x (1.5/100) = ?

Science
You guys are brilliant.

Chemistry
You do it this way. You're right; the oxidizing agent is reduced and the reducting agent is is oxidized. Oxidation is the loss of electrons and reduction is the gain of electrons. You have two problems so let's separate them. Here are the two in the problem that can be...

chemistry
Would you believe 30.0 x 79.7 cal/g = ?

Inorganic Chemistry
You can't oxidize Cu +2 ion. You can reduce it to Cu^+ or Cu^o but not oxidize to Cu^3+ or higher. Your first and last posts are at odds. The first one can Cu ion oxidize...... and the last one was what can oxidize Cu ion.

Inorganic Chemistry
I understand your question but the answer is "take your pick". If you want to oxidize SO2 the only choices would be SO3 I would think although thiosulfate could be another possibility. The environment could make a difference, too (aqueous solution or not etc). My gut...

Inorganic Chemistry
Write and balance the equation, look up the E potentials, calculate E for the rxn. If you get + the rxn proceeds.

more----Chemistry to DrBob222
In other words, you calculate the change in density at 273 K instead of change in density at 300 K

Chemistry to DrBob222
And that way calculating it is not right. O2 is 1.42 x 273/300 = 1.30 CO2 is 1.956 x 273/300 = 1.79(rounded) [(1.79-1.30)/1.30]*100 = 37.7%

Chemistry to DrBob222
You must have made an error. I ran through both calculations and got the same densities so percent different must be the same. For O2 PM = dRT gives 1.30 for O2 and 1.79 for CO2. The first method we used was (but I left the final calculations to you): O2 = 32/22.4 x 273/300 = ...

Chemistry to DrBob222
Thanks to Writeacher for making that link easier to find. At first glance, it appears to me that you can. But why not just run it and see if it comes out the same. I think it will.

Chemistry
It isn't clear what ratios you want. Lat's assume you want ratio SO2/O2; SO2/CH4 but you could have other combinations. Choose an arbitrary rate for SO2 in say Liters/minute. Then plug into the formula for Graham's Law. (rate SO2/rate O2) = (MM O2/MM SO2) where MM ...

chemistry
See your post below. You didn't give us much time to answer before posting a duplicate.

chemistry
mols HCl = M x L = 1.00 x 0.050 = 0.050 mols NaOH = M x L = 0.050 Total volume = 100 mL qrxn = mass x specific heat x (Tfinal-Tinitial) = 100 g x 4.184 x (37.8-25.5) = ? J/0.050 mol HCl So how much is q for 1 mol?

chemistry
Cu + 2Ag^+ ==> 2Ag + Cu2+ mols Cu = grams/stomic mass = approx 15 but you need a more accurate answer than that estimate. Now convert mols Cu to mols Ag expected. That's approx 15 g Cu x (2 mols Ag/1 mol Cu) = approx 30 mols. How much Ag is that in grams? That's 30 ...

Forensic science
I don't agree that any of those choices are complex but the title "forensic science" makes me think you want the word fluorescence.

Thermodynamics
Thanks for sharing your answer. It is right. I obtained 390.5 watts.

Chemistry
See your other post below. You gave up too soon.

Chemistry
You need the answer to a to solve d. So I obtained 4.846E-19 J for the energy of the transition (part a). b. That translates to 410.2 nm for the wavelength. c. K.E. = hc/wavelength - work function. You know K.E. is 1.32E-19J. You know hc/wavelength from part a. Solve for work ...

ooops---Chemistry
I made a huge mistake. I guess I can't count. d electrons have l = 3 while p electrons have l = 2 so delta l is 1 and there is no violation. When I first read the problem I got it in my mind that the difference was 2. Funny thing about hour minds.

Chemistry
To start, an electron transition from a 6d to a 2p is forbidden because it violates the selection rule of delta l = +/- 1; however, if you will provide the answers that you say you can't get, I'll give it a shot.

@ real MathMate
I have had the same experience but I signed in with a program generated by Leo and I understand that it is now harder for imposters to use my name with an answer. I haven't had the problem since I signed on with that program. Writeacher has done the same.

science
Technically, adding an electron to an atom makes the atom and ion and adds the mass of an electron (about 9E-28 g which is quite small). but, yes, it does change. It does not affect the atomic number or the mass number but the atomic mass does change for ion but it is hardly ...

Chemistry
You did a lot of work, most of which is not right. Here is what you do. Use (P1V1/T1) = (P2V2/T2) P1 is 760 mm Hg P2 is 742 mm Hg V1 = 2.8 L V2 = 3.1 L T1 = 273+20 = 293 K T2 = ?. Solve for this and the answer will be in units of kelvin. By the way, note the correct spelling ...

chemistry
density Fe greater greater internal forces harder to break the crystal structure bonds

Chemistry
I'd like to know how you make molten NaHCO3. It decomposes. Also, I'm not sure I'd believe anything like this unless it was done before my eyes in living color.

chemistry
See it? You get 128 kJ for 4*1.01 g H. So how much will you get for 8.08?twice as much?

Chem 1
You would make a lot more sense if you wrote it this way. Cu + 2H2SO4 ==>CuSO4 + SO2 + 2H2O Remember the rules. Oxidation is the loss of electrons. Cu is 0 on the left and +2 on the right. S is +6 on the left and +4 on the right (with SO2) H is +1 on left and right(doesn&#...

Chemistry-titrations
If you are titrating to the first end point (about pH 8.3 or so), no, heating is not necessary. But if you are titrating to the second end point (pH about 5 or so with methyl orange or methyl red as indicator), yes. In the second case you titrate to the end point, heat to ...

more--Chemistry
I'm not sure I would call that a reaction, as such, but more like an interchange.

Chemistry
Some of the D will replace some of H atoms so you get a mixture of H2O, D2O, HDO.

Chemistry
Your reasoning appears valid to me.

Chemistry - percipitates
That didn't make sense to me either.

Chemistry - percipitates
My best guess about the addition of Ag2SO4 is that Ag2SO4 is not all that soluble (not all that insoluble either) but it provies a small amount of added Ag^+ to act as a common ion and reduce the solubility of AgI even more than it already is.

Chemistry - percipitates
I don't know the purpose of the procedure in your post. I need to know the purpose of the process but I can answer some of them. My best guess is that you are determining the Ksp for AgI. Adding Cl2 and heating probably is to oxidize some of the I^- in AgI to I2. KI is ...

chemistry
mols = grams/molar mass = ?

Chemistry - Naming
Si4Br8 is a polymer (4 of them together) of SiBr2 or silicon(II) bromide. I would call the polymer tetrasilicon octabromide.

Chemistry - Ionic Compounds
Ionic compounds form between metals and non-metals. You have Sr, Ca, Ga metals and Br and O non-metals. Examples: Br and Sr would be SrBr2. Br and Ga would be GaBr3. etc. with Br and other metals. Br and O would be BrO2 but BrO2 isn't that well known AND it isn't ionic...

@Ryan--Chemistry
Almost but not quite there. First, I assume that * meant a typo and the question was for 1.00E8 kg (NH4)2SO4. So 1E8 kg x (2*molar mass NH3)/molar mass (NH4)2SO4 That 2 is necessary because there are two NH3 molecules in (NH4)2SO4. Or to put it another way, the equation for ...

Chemistry
Technically, one needs a volume since M is substituted into the Kc expression and not mols. You don't have a volume listed. However, the volume cancels as follows: Kc = (mols HI/v)^2/(mols H2/v)(mols I2/v). That means we can assume any volume or ignore volume (or use 1 L...

Chemistry
(PCl5) = 1.5 mols/4 L = 0.375 M. 0.375 M x 0.35 = 0.131 M .......PCl5 ==> PCl3 + Cl2 I....0.375.......0......0 C.....-x.........x......x E...0.375-x......x......x Kc = (PCl3)(Cl2)/(PCl5) You know x is 0.131 M. Substitute and solve for Kc. Post your work if you get stuck.

Chemistry
My "no" meant that all of the work leading up to Al being the limiting regent is not right.

Chemistry

Biochemistry
I don't see any solutions.

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