Chemistry Forums for Students > Undergraduate General Chemistry Forum

Number of moles, molar mass and mass of an unknown substance

(1/4) > >>

Massimo:
Is it possible to calculate the number of moles (n), the molar mass (M) AND the mass (m) of a substance, if you don't know what the substance (Let's call it SUBSTANCE X) is? Example; I have 0.387 grams of CHLORIDE within 1 gram of a solution. What is the name and molar mass of the molecule that's taking up the remaining mass of the gram (0.613 grams)? I have been told to use the stoichiometric coefficients to work backwards to the solution... Which is 1(substance X)2Cl2

AWK:
Your problem has many solutions (XCl, XCl2 ...). You can limit them on the basis of salt solubility (e.g. you will never get such a concentration of NaCl).

Massimo:
Ok. Thank you for that. Do you know how I go about calculating the molar mass of the unknown substance, (M)?

AWK:
You need to collect the solubility data of different chlorides at the same temperature (your choice). Then you need to convert the solubility into the chloride content. All solutions that have higher content in the saturated state can be immediately discarded - maybe 2 or 3 will remain and for them, you need to complete the calculations. You know the mass of chlorides, and therefore the number of moles - that's a simple stoichiometry.

Borek:

--- Quote from: Massimo on July 02, 2020, 04:57:50 PM ---Example; I have 0.387 grams of CHLORIDE within 1 gram of a solution. What is the name and molar mass of the molecule that's taking up the remaining mass of the gram (0.613 grams)?
--- End quote ---

1 gram of SOLUTION or 1 gram of SOLUTE? Note that in the first case all you know is that the mass of the metal is lower than 0.613 g, you don't know what it really is.

As AWK wrote, this question can have no single answer.

Navigation

[0] Message Index

[#] Next page