Finding element X in an unknown compound

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Discussion Overview

The discussion revolves around a homework problem involving the identification of an unknown element X in a compound, given its mass percentage and molar mass. Participants explore the applicability of various equations related to moles and atomic weight in this context.

Discussion Character

  • Homework-related, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant attempts to apply equations for calculating moles but expresses uncertainty about the necessary values for element X.
  • Another participant suggests that the problem can be solved using basic math to find the mass of element X from its percentage in the compound, but they also note uncertainty about the existence of such an element based on the provided data.
  • A later reply reiterates the basic math approach but questions how to isolate the atomic weight of element X without knowing the number of atoms in the compound.
  • One participant proposes that guessing the number of atoms per molecule might be a valid approach, but they express skepticism about obtaining reasonable answers.
  • Another participant critiques the initial problem statement, suggesting it lacks clarity and that further guessing may not be productive.

Areas of Agreement / Disagreement

Participants generally disagree on the approach to solving the problem, with some advocating for basic calculations and others expressing doubt about the feasibility of finding a valid solution. The discussion remains unresolved regarding the identification of element X.

Contextual Notes

Limitations include the lack of clarity in the problem statement and the dependence on assumptions about the number of atoms in the compound, which affects the ability to determine the atomic weight of element X.

Saracen Rue
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Homework Statement


An unknown compound weighs 1.023 kg. It is known that element X composes 28.3% of the compound. Given that the molar mass is 240.5 g/mol, find element X.

Homework Equations


mole = mass / atomic weight
(n = m / Ar)


mole = mass / molecular weight
(n = m / Mr)

mole = number of particles / Avogadro's number
(n = P / NA)


The Attempt at a Solution


I tried solving using the first equation, but I don't know them mass, Ar or mole of element X. I solved for the mole of the substance using the second equation, but I don't know how to find the unknown element from there. I don't think the last equation is applicable in this particular case, but I included it just in case.
 
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Neither of the equations you listed is applicable here, answer is much more trivial.

Pretty basic math: you are being told x grams compose 28.3% of 240.5 g. How many grams is x?

Not that I know what the final answer is. Unless you did some mistake copying numbers, there is no element that fits.
 
Borek said:
Neither of the equations you listed is applicable here, answer is much more trivial.

Pretty basic math: you are being told x grams compose 28.3% of 240.5 g. How many grams is x?

Not that I know what the final answer is. Unless you did some mistake copying numbers, there is no element that fits.

I think I've worked out the problem. 28.3% of 240.5 g isn't actually giving the Ar of the element - it's giving the Ar of the element x the number of said element in the compound. I can't work out how I could find just the Ar on its own, without the number of the element factoring into the problem.
 
The only valid approach is to guess - assume there is a single atom, or two atoms, or three atoms per molecule and so on. Sadly, none of the numbers you will get gives a reasonable answer.
 
And then the first sentence of all makes no sense, and on any near guess as to sense it is irrelevant... I don't think we should try to guess further.
 

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