# Posts by DrBob222

Total # Posts: 55,187

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 ...

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.

chemistry

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

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 ...

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

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 ...

Chemistry
insufficient data.

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.

@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.

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.

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

Chemistry
See your other post above. Same idea.

Chemistry
600 = mass H2O x specific heat H2O x (Tfinal-Tinitial)

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 -. ...

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...

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 ...

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.

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

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...

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 ...

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

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 (...

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

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

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 = ?

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.

chemistry limiting reagent
That is correct.

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.

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 ...

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 ...

Chemistry
John, I don't believe you have all of the information listed. You can do b but not a or c with the information listed.

chem 1211
q in J = mass H2O x specific heat H2O x delta T. Careful that mass H2O and specific heat H2O are in the same units.

Chemistry
If Qsp > Ksp, a ppt will form. So what is Qsp? You are mixing two solutions. That changes the concentrations of both. To what? You are diluting 0.008 M K2SO4 from 650 mL to (650+ 175) = 825 mL. So final (K2SO4) = (SO4) = 0.008 x (650/825) = ? (Ag2SO4) = ? You don't know...

Chemistry
First I doubt you determined the wavelength. Probably the wavelength was set or you set it to some desired number. I suspect the 0.178 was the absorbance you read from the spectrometer. Any, one of that really matters. So M = 2.3E-5 what? Is that 2.3E-5 M Fe. I will assume so...

Chemisry
I don't think so. The black/green color is due to a little Cu that goes into solution. Rubbing HALF the Cu off and exposing the half Zn and half Cu surface still leaves some of the Cu to react.

chemistry
There are 6.022E23 atoms in a mole of atoms and 6.022E23 molecules in a mole of molecules. So 3.011E23 atoms x (1 mol/6.022 atoms) = mols He. b. I don't know. I suspect you made a typo and this is meant to be CO2. c. This is done the same way as part a. I don't get the...

chemistry
80 proof means 40% v/v alcohol. % v/v means 40 g solute/100 mL solution. So if 40 g alcohol are in 100 mL, how much is in 1000 mL?

just anothe way---chemistry
How many mols do you want? That's mols = M x L = 0.03 x 0.250 = 0.0075 mols. Then 0.0075 mols x 101 g/mol= ?

chemistry
1.07 g/mL x ?# mL x 0.10 = 18.50 g. Solve for ? mL.

chemistry
mols = grams/molar mass. You know molar mass and grams, solve for mols. Then M = mols/L. You know mols and M, solve for L.

Chemistry
a. q = mass H2O x specific heat H2O x (Tfinal-Tinitial) b. q = mass ice x heat fusion ice c. q = mass H2O x heat vaporization H2O

chemistry
What's STD?

Chemistry
Can't do it. You need the concentration of the FeSO4 solution.

Chemistry
AgNO3(s) + H2O --> Ag^+(aq) + NO3^-(aq)

Analytical chemistry
Because the Ag^+ will ppt with AgCl and Ag2SO4 is rather insoluble, also.

Chemistry (molarity)
mols = M x L = ?

Chemistry
Use mL1 x M1 = mL2 x M2 and it will work out OR, logic. Logic goes this way. 5.00M x (2.00/10.00) x (3.00/25.00) = ?

Chemistry (molarity)
I think the question MAY (that's MAY) not be worded properly. Two scenarios. 1. IF the question is stated properly, then the molarity of the KHP solution created by added 35 mL water instead of 25 mL water is decreased. As Mia notes, M = mols/L and if L is larger than M is...

chem
Actually I don't think it makes any difference; however, I like to write it as [Xe] 4f14 5d3 6s2 for this shows a plausible oxidation state of +5.

Chem 104
I'm sorry but I can't decipher this post. I see you want the molarity of the KHP solution but "mass per liter in 100 mL water" and "drop ml-20" don't mean anything to me.

CHEM 120
pH = pKa + log (base)/(acid) 9.00 = pKa + log b/a You get pKa from Kb. Convert Kb to pKb; then pKa + pKb = 14 and solve for pKa. Substitute (base) from the problem and solve for (acid), then convert (acid) to grams NH4NO3. Post your work if you get stuck.

chemistry

Chemistry

Chemistry

Chemistry
a. mols CO2 = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols CO2 to mols CH4. Now convert mols CH4 to grams. g = mols x molar mass = ? g CH4. b doesn't make sense. grams mols???

chemistry
Look up the electronegativity and subtract. The larger difference means a more ionic bond.

Chemistry
2NaOH + H2SO4 ==> Na2SO4 + 2H2O mols NaOH = M x L = ? Look at the coefficients in the balanced equation. 1 mol H2SO4 = 2 mols NaOH; therefore, mols NaOH/2 = mols H2SO4. Then M H2SO4 = mols H2SO4/L H2SO4. You know mols and L, solve for M.

Chemistry
Isn't this very close to this problem I showed you earlier? http://www.jiskha.com/display.cgi?id=1478745034

Chem 1020
Same type problem. http://www.jiskha.com/display.cgi?id=1478745034

Chem1020
http://www.jiskha.com/display.cgi?id=1478745034

Help?? Chemistry?
You've done step 1. Step 2. mols KOH = M x L KOH = ? Step 3. Using the coefficients in the balanced equation, convert mols KOH to mols H3PO4. You can see that mols H3PO4 = 1/3 mols KOH Step 4. Then M H3PO4 = mols H3PO4/L H3PO4 = ?

Chem 1020
The coefficients tell you that. 2.57 molx Na x (1 mol Na2O2/2 mols Na) = ? Note how mols Na in the numerator cancels with the mols Na in the denominator. That leaves mols Na2O2 in the numerator as the only unit left; you have converted mols Na to mols Na2O2.

Chemistry
KOH + KHP ==> H2O + K2P. mols KHP = grams/molar mass = ? Using the coefficients in the balanced equation, convert mols KHP to mols KOH. That's a 1:1 ratio; therefore, ? mols KHP = the same mols KOH. Then M KOH = mols KOH/L KOH. You know mols and L, solve for M

Chemistry
mass = volume x density. mass Zn = 1 x density Zn (you will need to look that up). mass Cr = 1 x density Cr. Look up density Cr also. Then subtract to find mass difference.

Chemistry
Mg + 2HOH ==> Mg(OH)2 + H2 mols Mg = grams/molar mass = ? Using the coefficents in the balanced equation, convert mols Mg to mols H2O Then grams H2O = mols H2O x molar mass H2O = ?

Chemistry
CaCl2 + Na2SO4 ==> CaSO4 + 2NaCl mols CaCl2 = M x L = ? Convert to mols Na2SO4. That is ?mols CaCl2 x (1 mol Na2SO4/1 mol CaCL2) = ?mols CaCl2 x 1/1 = ? Then M Na2SO4 = mols/L. YOu know M and you know mols, solve for L and convert to mL.

Chemistry
% w/w = (grams solute/grams solution) x 100 = ?

chemistry
What is your main problem with this question? Do you know what these compounds are? How they react with water?

Chemistry
Why don't you look up the Law of conservation of mass and see what it means?

chem 15
1 ppm = 1 mg/L; therefore, 175 ppm = 175 mg CaCO3/L. Convert to grams Ca ions. Convert to mols Ca M = mols Ca/L solution.

chem 15
%w/w = (mass solute/mass solution)*100 = ?

Chemistry
Check your post. Are you sure that is lead(IV) acetate and not lead(II) acetate. The ppt will be lead(II) chloride, PbCl2, and not PbCl4.

Chemistry
You make a set of standards (solution of known concentration of the molecule/ions you want to determine), run them through the same procedure you will use on the unknowns, then measure the absorbance of each. Plot A on the y axis and mg/mL on the x axis. That is your ...

Chem
Should be As^3-. Those extra electrons repel each other and the other electrons in the outside shell and that causes the ionic radius to be larger.

chemistry
Not so. mols P4 = 20/molar mass P4 = ? mols Pbr3 = ?mol P4 x (4 mols PBr3/1 mol P4) = ? For grams Br2, it isn't 2.93. mass Br2 = volume x density = 50 mL x 2.93 g/mL = ? Then mols Br2 = g/molar mass = ? Convert mols Br2, as above, to mols PBr3 . The smaller number will be ...

Weird question science
Right, but I don't know that it's such a weird question.

chemistry
mass = volume x density or vol = mass/density vol Au + vol Ag = total vol Let x = mass Au then 9.35-x = mass Ag (x/19.3) + (9.35-x)/10.5 = 0.654 Solve for x = mass Au, then x/19.3 = vol Au.

chemistry
See your other post above. We appreciate it when you use the same screen name; we can help you better and faster that way.

chem
1 = -log (H^+) so for pH 1, (H^+) = 0.1M and for 1 L of that, mols HCl = M x L = 0.1 x 1 = 0.1 mol. 2 = -log (H^+) (H^+) = 0.01 M and mols HCl = 0.01M x 1 L = 0.01 mols. Then 0.1 mol HCl - 0.01 mol HCl = 0.09 mols HCl to be removed. 2HCl + CaCO3 ==> CaCl2 + H2O + CO2 mols ...

Chemistry
Is this just a "I wonder what would happen if" from a bunch of kids sitting around at night with nothing to do except thing up absurd questions.

Chemistry
1. Write the balanced equation. C2H5OH + 3O2 ==> 2CO2 + 3H2O 2. Convert 760 g ethanol to mols. mols = grams/molar mass = ? 3. Using the coefficients in the balanced equation, convert mols ethanol to mols CO2. That's ?mols ethanol x (2 mols CO2/1 mol ethanol) = ? 4. ...

Chemistry
You're right that C = 4.22E-5 M. So M x L = mols = 4.22E-5 mol/L x 2E-3 L = mols X in that final 2 mL sample that was measured. But that also is the mols in that 300 uL taken from the original sample. Convert to grams. That is g = mols x molar mass = ? That gives you grams...

chemistry
You need to look up the solubility of NaCl in water at 80 C, then assign saturated, unsaturated, supersaturated

Chemistry
2H2O ==> 2H2 + O2 mols H2O = 4.307/18 = ? mols O2 = ?mols H2O x (1/2) g O2 = mols O2 x molar mass O2 = ?

Chemistry
Same problem as above. Just different numbers.

@ Steve--typo I think---chem.
I agree with almost all of your work. I also would agree that working it as a math problem is a lot easier than as a chemistry problem. I did it as a chem problem because it was labeled chem. While the mols Ar = 1.2 it is 1.2 both in the initial mixture as well as the final ...

chem.
Steve has worked this as a math problem (because he is a math person). I assume the title of chemistry for the question you may want to work it as a chemistry problem. Do it this way. BTW, I agree with Steve's answer EXCEPT for the 1.5 mols. If mols Ar are 1.2 in the ...

Chemistry
Since Sn ==> Sn^2+, then if M Sn^2+ is 0.65, so mols Sn^2+ = M x L = 0.65 x 0.023 = ? and same mols Sn to have started the process. Then g Sn = mols Sn x atomic mass Sn = ?

chemistry
CaCO3 + 2HCl ==> CaCl2 + H2O + CO2 mols CaCO3 = grams CaCO3/molar mass CaCO3 = ? mols CaCl2 = mols CaCO3 since 1 mol CaCO3 produces 1 mol CaCl2. Then g CaCl2 = mols CaCl2 x molar mass CaCl2 = ?

Chemistry Solutions
Your post just isn't clear. I can prepare almost any number of mL from 59 g NaOH but of WHAT concentration. Do you mean to start with 59 g NaOH and ask how many mL of 19.4M NaOH can be prepared from that? If so then mols NaOH in 59 g = grams/molar mass = 59/40 = 1.475 mols...

chemistry
0.025 mg = 25E-3 g Pb. mols Pb = grams Pb/atomic mass Pb. 1000 mL H2O x 1.00 g/mL = 1000 g = 1 kg. molality = mols Pb/kg H2O

chemistry
p = mv

chemistry
wavelength = h/mv

Chemistry
(P1V1/T1) = (P2V2/T2)

Chemistry
Also we assume that all of the ice melts. q1 = heat needed to raise T of cube at -13.3 to zero C. q1 = mass ice x specific heat ice x (Tfinal-Tinitial) q2 = heat needed to melt ice at zero C to liquid water at zero C. q2 = mass ice x heat fusion. q3 = heat needed to raise T of...

chemistry
Use PV = nRT. You know P, V, R and n. n = grams/molar mass. Solve for T (in kelvin).

chemistry
There is no reaction. Look up the solubility of these. KNO3 is soluble Ba(C2H3O2)2 is soluble. Now look at the possible products if they react as double displacement. KC2H3O2 is soluble and Ba(NO3)2 is soluble. Neither of the possible products is a gas. Neither is a weak ...

Chemistry 101
I don't know the details of the experimental set up.

chemistry
1000 is the volume of the solution. Since you want M, that means you want mols solute/L solution. 1000 is volume of solution. 1000 mL x density in g/mL = grams solution. 1000 x g/mL x (%/100) = grams solute. 1000 x g/mL x (%/100) x (1/molar mass solute) = M where grams solute/...