Identify 2 Unknown Elements in a Chemical Equation?

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Discussion Overview

The discussion revolves around identifying two unknown elements in a chemical equation involving a metallic element M and a diatomic element X2, based on given masses and moles. Participants explore the relationships between the substances involved in the reaction and attempt to deduce the identities of M and X through calculations and reasoning.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about how to approach the problem due to the lack of known elements for comparison.
  • Another participant suggests that knowing the moles of one substance allows for the determination of the moles of others, and that the mass given can be used to calculate molar mass.
  • Several participants calculate the molar mass of MX to be 143 g/mol and propose that M could be silver (Ag) with a molar mass of 107.8 g/mol, while X is suggested to be gallium (Ga) with a molar mass of 70.46 g/mol.
  • There is a correction regarding the calculation of moles of MX, with a later participant noting it should be 0.0474 instead of 0.0484.
  • One participant questions how to derive the molar mass of X from the known values of MX and M, leading to a discussion on using the equation MW(MX) = MW(M) + MW(X).
  • Another participant humorously interprets the term "silly" in the problem statement as referring to the silvery appearance of the metal.
  • There is a suggestion to calculate the grams of X2 from the difference between the total mass of MX and the mass of M.

Areas of Agreement / Disagreement

Participants generally agree on the calculations related to molar masses and the identities of M and X, but there remains some uncertainty regarding the exact values and the interpretation of the problem statement. Multiple competing views exist regarding the identities of the elements based on the calculations presented.

Contextual Notes

Some calculations depend on assumptions about the completeness of the reaction and the accuracy of the provided masses. The discussion includes corrections and refinements of earlier claims, indicating that participants are actively engaging with the problem and each other's reasoning.

Lori

Homework Statement


A silly sample of a metallic element M, reacts completely with 0.0237 mols of X2 to form 6.78 g MX. What are the identities of M and X?

Homework Equations



mols = grams/molar mass[/B]

The Attempt at a Solution


(kinda have no clue what to do because I'm not sure what to do. There aren't any elements to compare the unknown with !)

Here's the equation i got

M + X2 > MX
balancing it: 2M + X2 > 2MX

6.78g MX * (?)

I honestly don't know what to start with and would appreciate if someone gave me hints ! :(
 
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Hello,

As long as the reaction is complete and you know the moles of one of the substances, you automatically know the moles of the other substances.

The mass of one of them is given, so you can calculate its molar mass. This can lead you to the solution (search in periodic table).
 
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DoItForYourself said:
Hello,

As long as the reaction is complete and you know the moles of one of the substances, you automatically know the moles of the other substances.

The mass of one of them is given, so you can calculate its molar mass. This can lead you to the solution (search in periodic table).
I get that MX has a molar mass of 143 g/mol but that's not for separate elements!

Actually, i just figured out that i was given 5.11 grams of X?

Would M be Ag? I found its molar mass to be 107.8g/mol

I also found X to be Ga because i found its molar mass is 70.46 g/mol
(Im pretty sure i messed up! .-. I'll post my work when i wake up~ tomorrow xD)
 
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Lori said:
Actually, i just figured out that i was given 5.11 grams of X?
That helps.
Lori said:
Would M be Ag? I found its molar mass to be 107.8g/mol I also found X to be Ga because i found its molar mass is 70.46 g/mol
How did you get these values?
 
mfb said:
That helps.How did you get these values?
I was actually given 5.11 grams of M
 
0.0237 mols X2 * (2 mol MX / 1 mol X2)
=0.0484 mol MX

6.78g MX/0.0484 mol Mx =143 g/mol

0.0237 mol x2 * (2 mol M/2 mol X) = ?? Mols M

5 .11g M / ?? Mols M = 107.8 g/mol
 
Lori said:
I was actually given 5.11 grams of M
Okay, that makes more sense.
I agree with silver then.

The molar mass of X2 that you probably calculated earlier is fine as well - what does that imply for an atom of X?
 
Lori said:
0.0237 mols X2 * (2 mol MX / 1 mol X2)
=0.0484 mol MX

6.78g MX/0.0484 mol Mx =143 g/mol

0.0237 mol x2 * (2 mol M/2 mol X) = ?? Mols M

5 .11g M / ?? Mols M = 107.8 g/mol

You calculated the molar mass of MX to be 143 g/moland the molar mass of M to be 107.8 g/mol.
So you can calculate the molar mass of X directly from these data.

Beware: It is 0.0474 and not 0.0484 mols MX.
 
Lori said:
I also found X to be Ga because i found its molar mass is 70.46 g/mol

Beware: X2.
 
  • #10
Lori said:
Would M be Ag? I found its molar mass to be 107.8g/mol

That must be why the problem statement said: 'A silly sample of a metallic element M.'
silly = silvery :oldeyes:
 
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  • #11
I like Serena said:
That must be why the problem statement said: 'A silly sample of a metallic element M.'
silly = silvery :oldeyes:
Actually, i ready 5.11 g as Silly ! XD Look~
https://imgur.com/a/OdEcl
OdEcl
 
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  • #12
Funny, as 5.11 g is not necessary to solve the problem.
 
  • #13
Since there is 5.11 g of M and 6.78 g of MX in the products, can i subtract the two to get grams of X2?

So i can do 0.0237 mols X2 * (2moles X / 1 mole X2) = 0.0474 moles X

6.78 g - 5.11 g = 1.67 g X2

1.67 g X2 / (.0237 moles X2) = 70.46 g/mols X2 /2 = 35.23 g/mol of X = Chlorine (35.453 g/mol)
 
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  • #14
DoItForYourself said:
You calculated the molar mass of MX to be 143 g/moland the molar mass of M to be 107.8 g/mol.
So you can calculate the molar mass of X directly from these data.

Beware: It is 0.0474 and not 0.0484 mols MX.
How do you use just the molar masses to figure out X?
 
  • #15
Lori said:
How do you use just the molar masses to figure out X?
As long as MW(MX)=143 and MW(M)=107.8, you can use the equation MW(MX)=MW(M)+MW(X). The only unknown is MW(X).

From the MW (molecular weight) of X, you can define the chemical element X directly.
 
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  • #16
DoItForYourself said:
As long as MW(MX)=143 and MW(M)=107.8, you can use the equation MW(MX)=MW(M)+MW(X). The only unknown is MW(X).

From the MW (molecular weight) of X, you can define the chemical element X directly.
Oh ! ! that makes sense! Thanks! This confirms my answer too!
 

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