# Posts by DrBob222

Total # Posts: 55,581

chemistry
What is the molarity of the initial H2SO4? That's 1.8 g/mL x 1000 mL x 0.3675 x (1/98) = y N = 2*M Then mL1 x N1 = mL2 x N2 mL1 x yN = 500 x 3N Substitute and solve for mL1.

chemistry

chemistry
25% HCl means 25 g HCl in 100 g solution. volume of 100 g solution is mass/density. Substitute and solve for volume in mL, convert to L. Calculate mols HCl from grams HCl/molar mass HCl. Then M HCl = mols HCl/L solution. pH = -log(HCl) pH + pOH = pKw = 14. You have pH and pKw...

chemistry
mols NaOH = M x L = ? mols HCl = mols NaOH M HCl = mols HCl/L HCl. Convert mols to grams for g/L. g HCl = mols HCl x molar mass HCl.

Chemistry
http://www.chemteam.info/Redox/Redox.html

Science
6.00 g/cc is right. mass = v x d mass = 200 cc x 0.250 g/cc = ?

Chemistry Lab
1. Which alum are you preparing? There are several. You can read about them here. https://en.wikipedia.org/wiki/Alum Generally, a monovalent cation sulfate with a trivalent cation sulfate + 12 mols H2O of crystallization. K, Na, Al, Fe, Cr, etc. I don't know what you used...

Physical Chemistry
https://viziscience.com/chemistry-mole-concept/molarity-change-temperature/

Chemistry
molecular equation: CoCO3 + 2HI==> CoI2 + CO2 + H2O Turn this into an ionic equation. CoCO3(s)+ 2H^+ + 2I^- ==> Co^2+ + 2I^- + CO2 + H2O Net ionic equation: Cancel those ions that appear on both sides of the equation. What's left is the net ionic equation.

1 Out Of 100 Math Trick HELP PLEASE!!!
My dad taught me this trick when I was about 15 but WARNED me that to make it work the number you multiply and divide it by must be the same. There must be some other caveats too.

Chemistry
1 ppm = 1 mg/L For Zn, toxic level is 6.42E-2 mM. That is 6.42E-5 M = 6.42E-5 mols/L. So in 1 L solution we have 6.42E-5 mols and grams Zn = mols Zn x atomic mass Zn and that gives you grams Zn/L. Convert to mg Zn/L and that is that many ppm. grams Zn = m

Chemistry
Tricky...I don't want to write out ethylene glycol all the time so let's let eth stand for that. M solution = mols eth/L solution. How to get values to plug in. mols eth = gram/molar mass and you get grams from mass eth = volume eth x density eth. You know volume and ...

Chemistry
M = mols/L How many mols KCl are there? mols = grams/molar mass = ? How2 many L are there? That's mass H2O = volume H2O x density H2O. Solve for volume in mL and convert to L.

Chemistry
They are not related. Radio waves, x-rays, red light, green light, yellow light, travel at the same speed of 1E8 m/s. It is a general question but you are supposed to know that the speed is the same.

Chemisty
Ionic solutions conduct electricity very well if they are 100% ionized or weakly if not 100% ionized. Covalent compounds that don't ionize3 don't conduct electricity.

Chem
1 ppm = 1 mg/L

Chemistry
Then you made a math error because 3.00 x 0.175 = 25.0 x M2 solves to M2 = 3.00 x 0.175/25.00 and that's the same as 0.175 x 3.00/25.0 = ?

Chemistry
I use this. 0.175 M x (3.00/25.0) = ? You can use the dilution formula of mL1 x M1 = mL2 x M2 3.00 x 0.175 = 25.0 x M2 and solve for M2. Both will give you the same answrs.

oops--chemistry
I see I can't spell phosphorus either.

chemistry
Please note that P is spelled posphorus

chemistry
You may not have done it wrong depending upon what the units were. Na2O + 2HNO3 ==> 2NaNO3 + H2O You want 0.5 mol NaNO3; how much Na2O is needed? So 0.5 mol NaNO3 x (1 mols Na2O/2 mol NaNO3) = ? molNa2O. Then grams Na2O = mols Na2O x molar mass Na2O.

chemistry
Na2O + 2HNO3 ==> 2NaNO3 + H2O 1. 1.5 what? grams? tons? bushels? I didn't get 1.5 grams. 3. 00416 what? Show your work.

Chemistry
You need to know the solubility rules. Here is a set. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Equilibria/Solubilty/Solubility_Rules

Chemistry
I still want to know what your problem is in doing this.

chemistry
I would choose something like 50,000 J/mol for Ea, use the Arrhenius equation, and solve for k(rate). Then multiply k by 3D8 and calculate the new Ea. Compare the two.

chemistry
Use the Arrhenius equation. Pick a number, for example choose 50,000 J/mol for Ea, the redo the equation using 50,000-9000 = ? J/mol and see the ratio of the two k values you calculated. That will be the ratio (factor) you want.

Chemistry
You need to know the solubility rules. Here is a set. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Equilibria/Solubilty/Solubility_Rules

Chemistry
If I knew what you don't understand I can help you do that. I try not to give the answers. You don't learn that way.

Chemistry
What is your problem in knowing how to do this?

Chemistry (Acid Base)
Convert pH = 7.980 to (H3O^+) = ? mols/L. Convert pH = 9.870 to (H3O^+) = ? mols/L. Subtract to see the difference in mols. The pH is now 9.87 and you want to move it to 7.98, therefore, you must add acid and you want to add the mols difference. Sub

Chemistry

chemistry
I may be missing something here but I don't know why the second step of pptng the Mg(OH)2 is necessary since EDTA at pH of 10 titrates both Mg and Ca. millimols Ca + Mg = mL x M EDTA, then mmols x molar mass CaCO3 = mg CaCO3/100 mL. Convert to mg/L.

Chemistry
Here is a mnemonic to help with electron configurations. https://www.google.com/search?q=mnemonic+for+electron+filling&tbm=isch&imgil=EkNTrJFoFS3EqM%253A%253BEVsKBY8LWm_POM%253Bhttps%25253A%25252F%25252Fwww.slideshare.net%25252FMosheLacson%25252Felectronic-configuration&source...

Chemistry
a. no. b. Because the electron configuration is the same for both isotopes. c. How did Ar= 121.8 get in there? If you will go up to the Br isotope problem you posted, just follow what I did for that and you can do this one.

Chemistry
The total for 79 and 81 is 100% and the total for fraction is 1, so let X = fraction 79 and 1-X = fraction of 81. Then 79(X) + 81(1-X) = 79.9 Solve for X.

Che
See the mnemonic I posted for you above.

Chemistry
For #1, you could have explained better as to the meaning of your numbers. First, however, the volume can be anything because you don't state the temperature or pressure. If 24,000 is the number you are using for the volume of 1 mol at the conditions of the problem, then #...

Chemistry
See your post above. Same kind of stoichiometry problem.

Chemistry
What table above?

121
what formula?

Chemistry
OK. I see you did read my earlier post but didn't understand it. In sentence 3, "After a of the aluminum oxide is removed......" doesn't make sense. After a what is removed?

Chemistry
You didn't read my earlier response did you. Proof your post or you'll never get it answered. A word or some words are missing from the beginning of sentence 3.

chemistry
Buffer solutions keep the pH on dilution; non-buffered solutions do not. Do you know how to spot a buffered solutiion? A buffer is made of either a. a weak acid and its salt. b. a weak base and its salt.

chemistry
The only way I know to do this is to work each answer as a separate problem. a. H2A + Ba(OH)2 ==> BaA + 2H2O mols Ba(OH)2 = M x L = ? mols = grams/molar mass. You have mols from above and grams from the problem, solve for molar mass. If you get 200 for molar mass then a ...

Chemistry
I suggest you proof your post and correct the omission of word, or words, "After a ......of the aluminum...."

Chemistry
Bob Pursley worked a similar problem several years ago. Use this as an example. "moles silver: .0435*.04 moles sulfate:.02658*.1 To make Ag2SO4, from the above, one is limiting. So of the two inputs above, which will be limiting? chem."

chemistry
I don't see much chemistry in this question.

Chemistry
1. %w/w = (g solute)*100/mass solution. Substitute and solve for g solute. 2. mols = M x L = ? 3. See #1 above and solve for mass solution. Then mass solution = mass solvent + mass solute = ? Substitute and solve for mass solvent. 4. mols = M x L = ? Then mols = grams/molar ...

chem
You would do well to find the caps key on your keyboard and use it. What do you not understand about this. Here are the steps. 1. Write the molecular equation and balance it. You haven't balanced it yet. 2. Convert to the full ionic equation using the following rules: a. ...

boiling point determination
What are you doing in this experiment?

Chemistry-Organic
1. Longer chain means more tangling of the chain is possible. Look up IM forces in the text or on the web and try the other two yourself.

yfoyfoy
I don't see a question

chemistry
Please use the same screen name. You get better service that way.

chemistry
4.23% w/w means 4.23 g NaI/(4.23 g NaI + 95.77 g H2O) Then m = mols NaI/kg H2O. part 2. Again, 4.23% NaI means 4.23 g NaI/100 g solution. Density of the solution is 1.03 g/mL. volume of the 100 g solution = mass/density. Then M = mols NaI/L solution. Post your work if you get ...

chemistry
mols O2 = grams/molar mass = ? Convert mols O2 to mols MgO using the coefficients in the balanced equation. Now convert mols MgO to grams; g - mols x molar mass = ?

Science
It doesn't mean the two are the same. Try a different solvent or a mixture of solvents.

chemistry
I don't understand the question.

Chemistry
Evaporate the water.

Chemistry
What's your problem with this? The first one is K2SO3 and SO3 is -2.

@Damon--Science
great examples and gets to the heart

Science
no. Why do you think that?

Chemistry
Fe2O3 + H2O = 0.525 g Fe2O3 = 0.400 H2O must be 0.525-0.400 = 0.125 g

Chemistry
I don't see a question here.

Chemistry
HNO3 + NaOH ==> NaNO3 + H2O mols NaOH = M x L = ? mols HNO3 = mols NaOH (Note 1 mol HNO3 = 1 mol NaOH in the balanced equation) Then M HNO3 = mols HNO3/L HNO3

Chemistry
a. pH = -log(H^+) b. pOH = -log(OH^-); then pH + pOH = pKw = 14. YOu know pOH and pKw, solve for pH. c. See a and b above. Solve for pOH, then H^+ and OH^- Post your work if you get stuck.

Chemistry
molecular equation is Ba(OH)2 + 2HClO ==> Ba(ClO)2 + 2H2O Net ionic equation is 2OH^- + 2HClO ==> 2ClO^- + 2H2O

chemistry
Is that 1/A - 1/Ao = kt ?

Chemistry
I don't know what the problem is but something is wrong. The molar mass of vitamin c is 176. Please check your numbers and the post.

Chemistry
You must define a zeet.

chem 1110
The formula defining the energy levels of a Hydrogen atom are given by the equation: E = -E0/n2, where E0 = 13.6 eV (1 eV = 1.602×10-19 Joules) and n = 1,2,3… and so on. The energy is expressed as a negative number because it takes that much energy to unbind (ionize...

maths
Yes, indeed, it makes a difference if it is spilt or split (or slipt)

chemistry
Dissolve the PbO (or is that PbO2 or Pb3O4?) in HNO3, add Na2CO3 to ppt the PbCO3 making sure most of the HNO3 is neutralized, filter, wash ppt, dry.

chemistry
Does this make sense?

chem
There are 100 cm in 1 meter so in 1 cubic meter there are 100 x 100 x 100 cc in 1 m^3 and 1E6 is what you have.

chemistry
dHrxn = (n*dHo products) - (n*dHo reactants)

chemistry
Time to be honest. I'm too old to know what a SMR is!!!

chemistry
Yes, the first answer was wrong, too. AB = A + B + energy ......exothermic AB + energy ==> A + B....endothermic

chemistry
I agree with 1 but not 2.

chemistry

chemistry
right

chemistry
The half life is 3 days. You start with 100 g. So at the end of 3 days, 1/2 of it is gone and you're left with 50 g. At the end of another 3 days, another half is gone. What's left.

chemistry

chemistry
Are you guessing? Think about it. If you cut a piece of wood in the middle, what happens to the mass of each piece? What happens to the volume of each piece? Now the density of the wood is g/volume. You've changed the grams (to 1/2) and you've changed the volume (TO 1/...

chemistry
not c.

Chemistry
Change radius of 7.0E5 km to cm; then (4/3)*pi*r^3 = volume of star. Change mass 1E36 kg to g. Density = mass/volume Post your work if you get stuck.

science
two? n-butane isobutane

chemistry
yes. coefficient.

chemistry
yes

Physical Science
right

Chemistry
You made a typo. Volume sphere = (4/3)*pi*r^3 Using the volume, calculate the volume of the sphere, then density = mass/volume Post your work if you get stuck.

chemistry
This is a limiting reagent (LR) problem. This procedure will find the LR as well as finish the stoichiometry. 1. Write and balance the equation. 2a. Convert 5.07 g butane to mols. mols = grams/molar mass = ? 2b. Do the same and convert g O2 to mols. 3a. Using the coefficients ...

Physical Science
yes.P1*V1 = P2*V2

Physical Science
one, not wone

Physical Science
I agree with this one. The wone about kinetic I agree with too but my answer won't post.

Physical Science
I agree

chemistry
I agree

chemistry
Is that 20% by mass (w/w) or 20% by volume (w/v)? I assume since it's 400 grams that 20% is 20% w/w. 2o% w/w means 20 g solute/100 g solution' therefore, 400 g will solution will be just 4 x that or 20 x (400/100) = ? Concentration in what units. I assume you mean % w/...

Chemistry
cc x M = cc x M 250 x 0.10 = cc x 2.0 Solve for cc, pipet that amount from the 2.0 M stuff into a 250 cc container, add water to the mark, shake, stopper.

CHEMISTRY
What is step 7? For that matter what are steps 1 through 6? And what does all that have to do with NH4Cl and SiO2? We aren't privy to the experiment you conducted.