[Rutherford]

Problem: When a kidney stone was analyzed, the following data was obtained:

If a sample of the stone is treated with a strong alkali, a gas with a sharp smell is released. If another sample of the stone is treated with HCl, a gas is released. Which of the following compounds could composite the stone?
a) MgCO₃·CaCO₃
b) (NH₄)₂HPO₃
c) MgNH₄PO₄·6H₂O
d) Ca₁₀(PO₄)₆CO₃
e) Mg₃(PO₄)₂

Attempt: I thought of converting the mass percents to molar ratios and I got the following ratio:
1.5 : 10 : 1.5 : 1 : 24 : 7.5
Mg    Ca    N    C    H     P

Here I got stuck. What to do now?

[Arkcon]

Hmmm... hard to understand this particular question.  Are those options menat to be the only ones to match the analysis?  Or is it pick several?  One of them has to be the source of each element found, and the "sharp odor" is a dead giveaway.  You're going to have to work with a couple, and see whats left to work with.

[Rutherford]

The sharp odor means that ammonium ion is present.

I don't understand what you want to say with:
"One of them has to be the source of each element found,"
Why so? I can choose more than 1 compound.

"You're going to have to work with a couple, and see whats left to work with."
How do you mean? What couple to choose?

[Borek]

How do you mean? What couple to choose?

Any couple.

For example - does any mixture of a&b yield given composition? If not - it has to be either other mix, or mix of three compounds.

[Rutherford]

Okay, the nearest to the mole ration is the c/d mixture, and it is the answer, but the number of H atoms isn't 24, there are actually 16. Why is c/d the right answer then?