Here's problem number 1:
--Statement--
• Hydrogen and chlorine both have two naturally occurring isotopes:
 ¹H (1.0078 amu; abundance = 99.985 percent) and
 ²H (2.01410 amu; 0.015 percent abundance),
 ³⁵Cl (34.969 amu;  75.53 percent abundance) and
 ³⁷Cl (36.966 amu; 24.47 percent abundance).

--Question--
(a) How many peaks would be expected in a mass spectrum of HCl(g)?
(b) At what molecular weights will peaks be observed?
(c) What should be the relative intensities of the peaks?
--??--

A) Is it 4? (lucky guess?) I read somewhere that Bromine, Br₂ has 2 isotopes but with 3 peaks...i think because of 1 isotope joining with another isotope..

OUT OF CURIOSITY..if the question is on H₂ ...Will it have 3 peaks as well?

B and C)  i have no idea how to answer or guess what they are...
I STILL DONT KNOW HOW MANY PEAKS ARE PRESENT...
How do u find the relative intensities?

Here's Problem number 2:
• Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na₂CO₃ • xH₂O, where x is the number of moles of H₂O per mole of Na₂CO₃.

When a 2.558-g sample of washing soda is heated at 125°C, all the water of   hydration is lost, leaving 0.948 g of Na₂CO₃. What is the value of x?

...NO idea where to begin..

Well there is 2.558g Na₂CO₃ • xH₂O minus 0.948 g of Na₂CO₃ = 1.61 g xH₂O

...does the 125°C have anything to do with this problem of finding the value of x?...

Also i divide each of these grams by their amu to find their MOLES:
0.948 GRAMS of Na₂CO₃ = 8.944 X 10^-3 MOLES

1.61 GRAMS of xH₂O = 0.089345172 MOLES

What do i do next?

AM I suppose to convert them to moles?....i dunno how to begin to find x ...I think i still have some more questions..but these are the ones that concerns me now...

*edited to improve eligibility

list out all possible combinations of the H and Cl isotopes.

How do i kno if the combination is POSSIBLE?

If all H isotopes can combine with all Cl isotopes, then there are 4 Combinations/Possibilities right?
1) ¹H -- ³⁵Cl
2) ¹H -- ³⁷Cl
3) ²H -- ³⁵Cl
4) ²H -- ³⁷Cl

The molecular weights are just the superscripts added together…right?
So...
1) HCl = 36
2) HCl = 38
3) HCl = 37
4) HCl = 39

I hope i am right...Or do i have to add the amu together?
So...
1) HCl = 35.9768
2) HCl = 37.9738
3) HCl = 36.9831
4) HCl = 38.9801
...Which one is right to find the moler weights?...second one right?

(c) requires a bit of mathematics - probability. use the probability tree diagram to help calculate the relative intensities of the peaks.

PROBABILITY TREE DIAGRAM?…uh…what is it and how does that help?

Shouldn't i do something with the amu or the percent abundance???

HOW do i find the relative intensities of the peaks?

can you relate the experimental molar ratio to the stoichiometric ratio of products?

Thx the x = to 10...thx on that one

o yea...i still need *delete me*!!

Problem number 3:
• Nicotine, a component of tobacco is composed of C, H,
  and N. A 5.250-mg sample of nicotine was combusted,
  producing 14.242 mg of CO₂ and 4.083 mg
  of H₂O.
What is the empirical formula for nicotine?
If the substance has a molar mass of 160 ± 5 g, what is
  its molecular formula?

I started with .014242 g CO₂ and converted to 3.236 X 10^-4 MOl of C

Then i did the same thing with H₂O, converting it to 4.532 X 10^-4 MOL of H.

To find how much O atoms, i'll have to convert 3.236 X 10^-4 MOl of C and 4.532 X 10^-4 MOL of H to GRAMS and subtract them from 0.005250 g sample of nicotine...
BUT i CAN'T Because there are some O atoms and N atoms in that remainder of grams....HOW do i separate the O and N atoms from the remainder g?


Problem number 4:
• Gallium (GA) consists of two naturally occuring isotopes with masses of 68.926 and 70.926 amu.
a)How many protons and neutrons are in the nucleus of
   each isotopes?
b)The average atomic mass of Ga is 69.72 amu. Calculate
   the abundance of each isotope.

So... i kno that Ga has 31 protons
a) ⁶⁹Ga  and ⁷¹Ga  
    (are the atomic mass of the isotopes correct?)
B) HOW do i calculate the abundance?

    Isn't it something like:
   (68.926amu)*( %) + (70.926amu)*( %) = 69.72
how do i find out the ""
...well one of them i can substitute (1.0 - %)
…since + equals 1.0

Problem number 5:
• An element X forms an iodide XI₃ and a chloride XCl₃. The iodide is quantitatively converted to the chlorine when it is heated in a stream of chlorine:
  2XI₃ + 3Cl₂ => 2XCL₃ + 3I₂

If 0.5000 g of XI₃ is treated, 0.2360 g of XCl₃ is obtained.

a) calculate the atomic weight of the element X.
b) Identify the element X.

This problem seems easy..but i dont know how to begin since they gave me GRAMS..and i cant convert it into moles to make a mole to mole comparison... because i dont know what the element X is....

WHAT can i do?..How do i start to solve this problem?

I hope that is enough...5 Problems out of 45 that i have to complete...i wish that is all the problems i have to ask...if i ask any more it'll make me feel dumb....

THX FOR REPLYING!!! THZ FOR YOUR TIME!!! THX FOR YOUR *delete me*!!

Then what ways can i calculate the intensity from the info above..

also, the other questions are a bit hard also...

THX for the *delete me*!

o..ok..

Forget about problem number 3....that's not really important...i think i got the answer to that....THX

Nicotine 's
empirical formula:  C₅H₇N
molecular formula: C₁₀H₁₄N₂

The should be right....

i'm still working on problem 4 and 5....

This also an experiment 'with putting back'

What's a "putting back"?...or what does that mean?

-----------------------------------------------------------

Thus the chance for 1 black and 1 white = (5/12 * 7/12) + (5/12 * 7/12)

Now the same can be done for the isotopes if you know the percentage of being in nature and consider that as the chance to encounter that isotope in the compund. This also an experiment 'with putting back'

Isnt that what i'm trying to do with problem number 4 b)?
BUT i dont know the abundance...HOW can i find the abundance from the info posted from problem 4?

(68.926amu)*( %) + (70.926amu)*( %) = 69.72


Can i just put a "not enough Info" sign on that question?

if they didnt tell me what the abundance is...how am i suppose to find it??

well..i could use pure math..if i kno how…

yea..that's what i was talking about..

are u sure that it is ⁶⁹Ga  and ⁷¹Ga

i kinda guessed it is those since the amu is the closest to those....

and to solve that..do i need to us edistrubutive property??..i forgot how to solve that....

i kno i have to take something out by dividing each side by something..

are you familiar with algebra mathematics?

let M be the molar mass of element X

.how do i find the relationship between those two GRAMS?

2XI3 + 3Cl2 => 2XCL3 + 3I2

Can't you tell from the equation that the number of moles of XCl3 produced equal the number of moles of XI3 consumed?

Express the number of moles of XI3 consumed in terms of M
Express the number of moles of XCl3 produced in terms of M

assuming 100% conversion,

molar mass of XI3 = M + 3(126.90) = M + 380.70 amu
number of moles of XI3 consumed = 0.500/(M+380.70)

molar mass of XCl3 = M + 3(35.5) = M + 106.5 amu
number of moles of XCl3 produced = 0.2360/(M+106.5)

0.500/(M+380.70) = 0.2360/(M+106.5)

solve for M