Can the amount of moles in a mixture be determined using mass and molar mass?

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Discussion Overview

The discussion revolves around whether the amount of moles in a mixture of two solids (NaCl and C12H22O11) can be determined using the total mass of the mixture and the molar masses of the components. The scope includes conceptual reasoning and mathematical reasoning related to mixtures and moles.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant questions the validity of calculating moles by multiplying the total mass by the inverse of the sum of the molar masses of the components.
  • Another participant argues that without knowing the fraction of each component in the mixture, it is not possible to determine the moles accurately.
  • A different perspective suggests that if the goal is to find the total moles of solution present, the fractions may not matter, although this is contested.
  • One participant illustrates the issue with an example of varying percentages of two components in a mixture, indicating that different compositions yield different total moles.
  • A further analogy is presented comparing the situation to a mixture of vehicles, emphasizing the difficulty in determining quantities without knowing the proportions of each type.

Areas of Agreement / Disagreement

Participants generally agree that the lack of knowledge about the fractions of each component complicates the determination of total moles in the mixture. However, there are differing views on whether it is possible to find total moles of solution without this information.

Contextual Notes

The discussion highlights limitations related to assumptions about the composition of the mixture and the implications of varying proportions on the total moles calculated.

fk378
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General question:

If given the mass (15.0 g) of a mixture of two solids (NaCl + C12H22O11), can I find the amount of moles in the mixture by multiplying (15.0 g)*(mol / mass NaCl + mass C12H22O11)? I don't think this is valid, but I don't know why not...
 
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i don't think you can really do that... mainly because you don't know what fraction of the mixture is NaCl or C12H22O11.
 
Well what if you're just trying to find the moles of solution present? Then would it matter the fraction of each?
 
well.. that is sort of impossible to say the total moles of "solution present". for example, try making up your own values for a solution... like 20% A (molar mass 20) and 80% B (molar mass 5). you could then find find moles A and moles B and add them up together to find total moles.
now try doing it again except with like 50% A and 50% B. You should get a different number of moles.. at least i hope so lol
 
Suppose I told you there was 1000tons of vehicles in the car park and they were a mixture of 0.5t Smart Cars and 10t Buses - you couldn't work out how many vehicles were present.
 

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