Wednesday
January 18, 2017

Posts by DrBob222

Total # Posts: 53,868

Chemistry
I think it's important that you define what you mean by 80:20 mixture. Is that 80:20 by mass, by moles, or by volume?
November 20, 2016

chemistry
a. What are you talking about. What subject, what experiment, what source? b. What sources have ALREADY been mentioned?
November 20, 2016

Chemistry 20
The 1.82 is 100%. That is theoretical yield (TY). The 1.94 is actual yield (AY) % yield = (AY/TY)*100 = ? You can take the difference.
November 20, 2016

Chemistry 20
Technically, none since H2CO3 decomposes as fast as it is formed. H2CO3 ==> H2O + CO2. However, ignoring that, then 2HNO3 + Na2CO3 ==> 2NaNO3 + H2CO3 The equation tells you that 2 mols HNO3 will produce 1 mol H2CO3. So 1.2E-3 mols will produce ......?
November 20, 2016

Chemistry 20
This is done the same way as the HNO3 problem.
November 20, 2016

chemisty
Cu + 2AgNO3 ==> Cu(NO3)2 + 2Ag mols Cu = grams/atomic mass = ? mols Ag = 2x mols Cu
November 20, 2016

Chem1020
Use PV = nRT. You know V(in L), n,R and T(in kelvin). Solve for P in atm and convert to mm. 1 atm = 760 mm Hg.
November 19, 2016

Chem1020
PV = nRT. You know P(must be in atm), V(must be in L), R and T(must be in kelvin). Solve for n = mols. Then n = grams/molar mass. You know n and grams, solve for molar mass.
November 19, 2016

Chemistry
dE = 2.18E-18(1/x^2 - 1/10^2)
November 19, 2016

Chemistry
50 g x (atomic mass Cu/molar mass CuO) = ? g Cu.
November 18, 2016

Chemistry
You need Keq and the reaction for that K.
November 18, 2016

chemistry
dT = 15 x (6/2) = /
November 18, 2016

Qualitative analysis
copper carbonate
November 17, 2016

Qualitative analysis
All form a hydroxide insoluble in water. Pb^2+ is the only one to form Pb(OH)2 which dissolves in an excess of NaOH by forming a complex ion of [Pb(OH)4]^2-
November 17, 2016

oops--Qualitative analysis (Chem)
Fe)OH)2 is green and gelatinous with white streaks and changes to a red/brn.
November 17, 2016

Qualitative analysis (Chem)
Al(OH)3 is not colored. Cu(OH)2, Fe(OH)2 and Fe(OH)3 are colored. Fe(OH)2 is the only one that is colored and changes color on standing because it is being oxidized to Fe(OH)3 by air. So Fe(OH) is greenish and it changes to a red/brown.
November 17, 2016

Chemistry
React with what to form what? I assume that is to decompose to H2 and O2 but I don't know that. Write the equation. 2H2O ==> 2H2 + O2 546.234 mols H2 x (2 mol H2O/2 mol H2) = 546.234 x (2/2) = 546.234 x 1/1 = 546.234 mol H2O. It's done with the coefficients. 2H2O
November 17, 2016

Chemistry
CH4 1 mol CH4/4 mol H or 4 mol H/1 mol CH4
November 17, 2016

Chemistry
I don't know what the C stands for but you seem to have ignored it in the calculation. I didn't go through the calculations with a calculator but the methods seems OK EXCEPT that you haven't added in the heat from steam at 100 to steam at 110
November 17, 2016

chemistry
melting ice at zero is mass ice*heat fusion = ? Cooling 540 g water from 25 to zero is mass H2O * specific heat ice x (Tfinal-Tinitial). Put those together to obtain (mass ice*heat fusion) + (mass H2O x specific heat water x (Tfinal-Tinitial) = 0 Solve for mass ice.
November 17, 2016

Chemistry
I said you were right yesterday.
November 17, 2016

chemistry
What are the conditions? T, P? I will assume STP but technically this problem can't be worked without that informatiion. 1.7 dm-3 H2 produced. Convert to mols. That's 1.7 x (1 mol/22.4 dm-3) = ? Convert to mols Zn. mols Zn = mols H2 (look at the coefficients in the ...
November 17, 2016

chemistry
g C = 1.500 g CO2 x (atomic mass C/molar mass CO2) = ? g H = 0.401 g H2O x (2*atomic mass H/molar mass H2O) = ? g O = 1.00-g C - g H = ? Convert grams to mols. mols C = g C/12 = ? mols H = g H/1 = ? mols O = g O/16 = ? Find the ratio of the elements to each other with the ...
November 17, 2016

Chemistry
What's Ksp for CaCO3? What's (H3O^+)?
November 17, 2016

Chemistry
thio (sulfur) compounds pyridines (N compounds)
November 17, 2016

Chemistry
mass = volume x density. You know mass and density, substitute and solve for grams.
November 17, 2016

@CaSO4...chemistry
You are removing products. Le Chatelier's Principle says that if a system in equilibrium is disturbed, then the system will shift so as to undo what we did to it. Therefore, it we remove the products, more CaSO4 will decompose to form the products we removed. You can take ...
November 17, 2016

chemistry
Please don't post another question as an answer to another question. A. See below for ethanol problem. B. Convert 2 kg glucose to L ethanol formed using the same procedure used in the previous problem. This will give you the theoretical yield (TY)( that's the yield as...
November 17, 2016

chemistry
C6H12O6(aq) ? 2 C2H5OH(l) + 2 CO2(g) mols glucose = grams/molar mass = ? mols ethanol = 2x that (look at the coefficients in the balanced equation). g ethanol = mols ethanol x molar mass ethanol. Convert to mL. volume in mL = grams/density.
November 17, 2016

Organic chemistry (QA)
This is hardly organic chemistry. Some reasons for pptn rxns. 1. A ppt is formed. 2. A gas is formed. 3. A weak electrolyte is formed. You asked only about pptn so look at the equations and see if a ppt will form. Basically this requires that you know the solubility rules for ...
November 17, 2016

Chem
First, you can NOT write an equation because you don't know the formula of gold chloride not the formula of gold nitrate.. The Cl in gold chloride was converted to AgCl. So how much Cl must have been there with the gold? That's 464 mg x (atomic mass Cl/molar mass AgCl...
November 17, 2016

Chemistry
I agree with you.Book must be wrong.
November 16, 2016

Chemistry
A. mols Al = grams/atomic mass = ? This is n in part B. B. Use PV = nRT. You know n, R, V and T. Remember V is in L, T in kelvin, R=0.08205. Solve for P in atm. C. Ptotal = pH2 + pH2O. Ptotal and pH2O are given. Solve for pH2.
November 16, 2016

chemisty
I assume you want an equation. 2Na + I2 ==> 2NaI
November 16, 2016

chemistry
1/(2E5)^3 = 1/(2E15) = 1.25E-16
November 16, 2016

Chemistry
I would assume 20 g Ne and 20 g He (but any number will do as long as it is the same for both). mols Ne = grams/atomic mass = ? mols He = grams/atomic mass = ? Total mols = ? XNe = mols Ne/total mols pNe = XNe*Ptotal = ?
November 16, 2016

Chemistry
Whatever number you choose, I guess, since you didn't post any conditions.
November 16, 2016

Chemistry
I worked this for you yesterday. http://www.jiskha.com/display.cgi?id=1479258354
November 16, 2016

Chemistry
I need more info than that.
November 16, 2016

chemistry
q = mass H2O x dHvap.
November 16, 2016

Chemistry
How can we help you with this without doing all of the work?
November 16, 2016

Chemistry
mols Al(OH)3 = grams Al(OH)3/molar mass Al(OH)3 = ? To do part b just rearrange the equation above to grams = mols x molar mass and substitute the data for Mg(OH)2. Remember to convert grams to mg at the end.
November 16, 2016

Chemistry
You're right. They are that.
November 16, 2016

Chemistry
Your abswer if 7 g makes no sense since specific heat is measured in J/g*C (or KJ)or cal/g*C. I'm not sure the problem can be worked without knowing the calorimeter constant.
November 16, 2016

Chemistry
CaCO3 ==> CaO + CO2 Use PV = nRT and solve for n for CO2 Convert mols CO2 to mols CaCO3, then to grams CaCO3 Finally, multiply g CaCO3 by 2 since it is only 50% pure.
November 16, 2016

chemistry
Just add the electrons, protons will be the same, look up the atomic number.18+2+10+4 looks like 34 = Se to me.
November 15, 2016

@A--Chemistry
Probably you should show your work. I don't buy those numbers. And yes, limiting reagent is a factor.
November 15, 2016

chemistry
https://answers.yahoo.com/question/index?qid=20081102155715AAfdYzQ
November 15, 2016

Chemistry
ka1 = (H^+)(HC2O4^-)/(H2C2O4) ka2 = (H^+)(C2O4^2-)/(HC2O4^-) You get (H3O^+) from pH. You're given C2O4^2- and H2C2O4. Plug and chug.
November 15, 2016

Chemistry
I found pKa for the base to be 7.76; therefore, = 7.76 + log (0.02/0.02) so the pH of this solutiion is 7.76 and no HCl needs to be added/
November 15, 2016

@Kitty A.----Chemistry
It seems several students think by using both boys and girls names we will think they are different people. Not so. How do we know the same person is using different screen names. Easy. The IP address, which shows when the question/response is posted, tells us the computer ...
November 15, 2016

Chemistry
Ms. Sue is right. You get faster and better help if you don't change screen names. 2CaO + 2SO2 + O2=> 2CaSO4 mols SO2 - 1E6/molar mass SO2 = ? Using the coefficients in the balanced equation, convert mols SO2 to mols CaSO4. Now convert mols CaSO4 to grams. g CaSO4 = ...
November 15, 2016

Chemistry
2K3PO4 + 3CoCl2 ==> Co3(PO4)2 + 6KCl
November 15, 2016

Chemistry
See your other posts.
November 15, 2016

Chemistry
This is just another stoichiometry problem. Find your post above and follow the same guidelines.
November 15, 2016

Chemistry
C'mon. You're wasting our time. See your other posts.
November 15, 2016

Chemistry
See your other post.
November 15, 2016

Chemistry
I balanced that Co and phosphate equation for you. What is it you don't understand about these equations? I can help do one but if you have problems we need to know how to help so you can do these yourself.
November 15, 2016

Chemistry
Didn't I do this for you a couple days ago? http://www.jiskha.com/display.cgi?id=1479076160
November 15, 2016

Chemistry
What reaction below? See here. https://www.webelements.com/lawrencium/
November 15, 2016

chemistry
N2 + 3H2 ==> 2NH3 With gases one can take a shortcut and work the problem as if volume = mols. 12 dm3 H2 x (2 dm3 NH3/3 dm3 H2) = 8 dm3 NH3 if the yield were 100%. It formed 2 dm3; therefore, %yield = (2/8)*100 = ?%.
November 15, 2016

Chemisty
1 mol salicylic acid = 1 mol aspirin; so .......
November 15, 2016

chemistry
You get 393.5 kJ for 12 g C. You want 39.3 kJ; therefore, (393.5 kJ/12 g C) x #g C = 39.3 kJ. Solve for #g C.
November 15, 2016

Chemistry
Hints: you must supply the details. A. Add dil HCl and observe bubbles CO2. Add BaCl2 after all of the CO2 has been released. B. Add BaCl2 C. Acidify the solution, heat to drive off CO2, add AgNO3. Cations: A flame test B. flame test C. Add concentrated NaOH.
November 15, 2016

Chemistry
heat gained by cold water + heat lost by hot coffee = 0 [mass cold H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass coffee x specific heat coffee x (Tfinal-Tinitial) = 0 Substitute and solve for mass cold H2O, then convert to mL. mass = volume x density. You know density ...
November 15, 2016

Chemistry
Hz. c = f*w = frequency x wavelength. freq is measured in Hz and wavelength in meters. c is speed of light = 3E8 m/s
November 15, 2016

Chemistry
195 kcal/hr x #hr = 145 kcal Solve for hr and convert to minutes. #hr x (60 min/hr) = # min
November 15, 2016

Chemistry
Use PV = nRT and solve for n = mols. Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
November 15, 2016

Chemistry
This is a limiting reagent (LR) problem; you know that because amounts are given for BOTH reactants. mols Cu = grams/atomic mass = ? mols HNO3 = M x L = ? Using the coefficients in the balanced equation, convert mols Cu to mols NO. Do the same and convert mols HNO to mols NO. ...
November 15, 2016

Chemistry
Two ways to do this, one short way and one long way. Long way. CaCO3 ==> CaO + CO2 mols CaCO3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaO. Then convert to g CaO. g CaO = mols CaO x molar mass CaO. Short way. 20 g ...
November 15, 2016

chemistry
heat lost by Co + heat gained by H2O = 0 [mass Co x specific heat Co x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial) = 0 Subsitute and solve for Tf which is the only unknown in the equation.
November 14, 2016

chemistry
See your other post.
November 14, 2016

chemistry
%H2O = [(5*molar mass H2O/molar mass CuSO4.5H2O)]*100 = ?
November 14, 2016

Chemistry
You are right that mols = grams/molar mass. I think your problem, often the problem with on-line values from a data base, is that you have reported an answer with too many significant figures. 222/98.0 = a max of 3 places. You have reported 4. Round that to 2.26 (or 2.27 ...
November 14, 2016

Chemistry
(H3O^+)(OH^-) = Kw = 1E-14
November 14, 2016

Chem
pH of NaF solution is determined by the hydrolysis of the F^-. .......F^- + HOH ==> HF + OH^- I.....0.1.............0....0 C......-x.............x....x E....0.1-x............x....x Kb for F^- = (Kw/Ka for HF) = (x)(x)/(0.1-x) and solve for x = (OH^-). Convert to pH. The ...
November 14, 2016

Chemistry
insufficient data.
November 14, 2016

oops typo---Chemitry
So you need 1 mole of Ca(OH)2 for every mole of HCl. Should be. So you need 1 mol Ca(OH)2 for every 2 mols HCl. The Conversion factor is ok.
November 14, 2016

@Dr Dave--oops--Chemistry
Total mass = 15x5 = 75g of BaTi(SiO3)3 should be 15 carats x (1 g/5 carats) = 3 grams and go from there.
November 14, 2016

Chemistry
H2A + 2NaOH ==> Na2A + 2H2O mols NaOH = M x L = ? mols H2A must be 1/2 that (look at the coefficients). mols H2A = grams/molar mass. You know mols and grams, solve for molar mass.
November 14, 2016

Chemistry
1250 J = mass H2O x specific heat x (Tfinal-Tinitial) Solve for Tf.
November 14, 2016

Chemistry
See your other post above. Same idea.
November 14, 2016

Chemistry
600 = mass H2O x specific heat H2O x (Tfinal-Tinitial)
November 14, 2016

chemistry
dE = q+w = dH-p(V2-V1) If dE is + and dH is -, then w MUST be + so -p(V2-V1) must be + With dH is - then heat must be released. That means A and B can't be right. The answer must be C or D. To make -p(V2-V1) +, must V2 or V1 be the larger number? If V2>V1, the w is -. ...
November 14, 2016

chemistry
Did you proof read your post? Probably not. The reaction produces ZnS which is zinc sulfide. (or sulphide). Do you intend to say that 16.2 g Zn reacts? I will assume so. So what is O at 16. Is this forming ZnS or ZnSO4. I will assume ZnS. a. Zn + S ==> ZnS b. mols Zn = 16.2...
November 14, 2016

Chemistry
I have no idea what the term "two concentration tables" means. However, I assume the problem wants you to calculate concn HBrO, H3O^+, etc. First, CsBrO is the salt of a strong base (CsOH) and a weak acid (HBrO). The BrO^- is a strong base and hydrolyzes in aqueous ...
November 14, 2016

chemistry
Balance the equation first. Fe2O3 + 6HCl = 3H2O + 2FeCl3 mols Fe2O3 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols Fe2O3 to mols FeCl3. Now convert mols FeCl3 to grams. grams FeCl3 = mols FeCl3 x molar mass FeCl3.
November 13, 2016

Chemistry
heat lost by hot water q = mass hot water x specific heat H2O x (Tfinal-Tinitial)
November 13, 2016

Chemistry
It's wrong because you have assumed that LiClO is a strong acid. It is not. It is the salt of a strong base (LiOH) and a weak acid (HClO). As such it hydrolyzes and the weak acid part (ClO^-) does this. ......ClO^- + HOH ==> HClO + OH^- I.....0.47.............0......0 C...
November 13, 2016

Chemistry (molarity) (sorta an emergency)
Your way is correct but I would suggest you not use the approximations but actual calculated values and keep the number of significant figures correct. Bob Pursley is absolutely correct, also. The main reason today's teachers don't use that method is because normality ...
November 13, 2016

Chemistry
(92 mg glucose/100 mL) x 5,100 mL = ? mg/5.1 L. Convert mg to g.
November 13, 2016

Chemistry
Take a 100 g sample and that contains 74.2 g C 8.64 g H 17.2 g N Convert to mols 74.2/12 = ? 8.64/1 = ? 17.2/14 = ? Now find the ratio of these three elements to each other with the lowest number being 1.00. The easy way to do that is to divide the smallest number by itself (...
November 13, 2016

Chemistry
0.04 mols SiO2 x molar mass SiO2 = grams SiO2. Then ? g SiO2 x (5 carats/1 g) = ? carats.
November 13, 2016

Chemistry
(1E5 rxns/sec) x (60 sec/min) x (60 min/hr) x (24 hr/day) = ?
November 13, 2016

Chemistry
q1 = energy needed to raise T from 20 C to 100 C. q1 = 1000g x 4.184 J/g*C x (100-20) = ? q2 = heat needed to boil 1,000 g H2O at 100 C. q2 = 1000 x heat vaporization in J/g = ?
November 13, 2016

Chemistry
n = 2, the second shell can hole 8 electrons. n = 5, l = 3. If l=0 that is an s electrons; if l = 2 that is a p electron and if l = 3 that is a d electrons. There can be 10 d electrons. n = 6, l = 1, ml = -1. You try this one.
November 13, 2016

chemistry limiting reagent
That is correct.
November 13, 2016

chemistry
The green color comes from the Cu; therefore, if there is no Cu and only Zn, there will be color because Zn(C2H3O2) is not colored.
November 13, 2016

chemistry
I believe you have the right idea but what you have written will not work. Using SCN^- as the limiting reagent will assure that all of the SCN^- is used but all of the Fe^3+ will NOT be converted. (Depending upon the amount of SCN and Fe used, some of the samples of Fe may be ...
November 13, 2016

Chem
a. Call phenol HP. mols HP = grams/molar mass = approx 0.04 but you need a better number than that. Then M = mols/L = 0.04/0.065 = approx 0.6 .....HP ==> H^+ + P^- I...0.6.....0......0 C....-x.....x......x E...0.6-x...x......x Substitute the E line into Ka for phenol and ...
November 13, 2016

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