[achibaby1974]

Okay. More online HW.

1.) I don't understand this one.
Name each of the following compounds.

(c) Co2S3
I have tried:
Cobalt (III) Sulphide
Dicobalt trisulphide

And it says both of those are wrong.

These don't make much sense either. I put my wrong answer underneath.

2.) Write the formula for each of the following compounds. (Type your answer using the format CO2 for CO2.)

(c) sodium dihydrogen phosphate
[NaH2]3 PO4 --------

(e) chromium(III) carbonate
Cr2 [CO3]3

(g) ammonium acetate
NH4 [C2H302]

(h) ammonium hydrogen sulfate
[NH]2 HSO4

(i) cobalt(III) nitrate
Co [NO3]3

I don't really know what's wrong with these answers. Do y'all see any?
P.S. I don't really even know the correct way to actually write this. The only example is for sulfite, type it as [SO3]2-


3.) Silver has two naturally occurring isotopes,107Ag (isotopic mass 106.90509 amu) and 109Ag (isotopic mass 108.90476 amu). If silver has an atomic mass of 107.87 amu, what is the percent abundance of each isotope?

107Ag
 %
109Ag
 %

I don't even understand the question. Is this asking for percent recovery? What is percent abundance? Is there a formula? Is it maybe:

107.87-106.90509/107.87 x 100 = .894511912 = .89451%?

I have no idea. There's nothing in our book and we haven't gone over it. I'll google it in the meantime.

Thanks for any help.

[Kryolith]

(c) Co2S3

Cobalt(III) sulfide?

(c) sodium dihydrogen phosphate
[NaH2]3 PO4 --------

Na is +I, what's the formula of phosphoric acid/phosphate?

(e) chromium(III) carbonate
Cr2 [CO3]3

Cr₂(CO₃)₃

(g) ammonium acetate
NH4 [C2H302]

Acetate is CH₃COO^-, did you type "0" instead of "O"?

(h) ammonium hydrogen sulfate
[NH]2 HSO4

What's the formula of the ammonium ion?

(i) cobalt(III) nitrate
Co [NO3]3

Co(NO₃)₃ is correct. You probably used a wrong format for your input.

I don't really know what's wrong with these answers. Do y'all see any?
P.S. I don't really even know the correct way to actually write this. The only example is for sulfite, type it as [SO3]2-

I don't know how the online interface works, I can just help you to tell whether your answers are correct or not.

[Kryolith]

3.) Silver has two naturally occurring isotopes,107Ag (isotopic mass 106.90509 amu) and 109Ag (isotopic mass 108.90476 amu). If silver has an atomic mass of 107.87 amu, what is the percent abundance of each isotope?

Elements occur in different isotopes with a specific abundance. The molar mass listed in your periodic table is the average mass. Example:

Element E has two isotopes with the molar masses M1 (abundance 30%) and M2 (abundance 70%). Its molar mass is 0.3*M1+0.7*M2. Due to the fact that you are usually looking at more than e.g. 10²⁰ atoms/molecules this statistically determined value gives you the correct mass.

I hope my phrasing is somewhat comprehensible.

EDIT:
Sorry for answering my own post. I wanted to edit the previous one...

[kerby99]

In the case of...."Chlorine has two naturally occurring isotopes,35Cl (isotopic mass 34.9689 amu) and 37Cl (isotopic mass 36.9659 amu). If chlorine has an atomic mass of 35.4527 amu, what is the percent abundance of each isotope?"

    34.9689*x%+36.9659*(100-x)%=35.4527

then x=0.75773...

so, the answer is 35Cl;76% and 37Cl;24%

This is how to calculate the percent abundance of isotopes.