How Much Iron is in a 250ml Glass of Milo?

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Discussion Overview

The discussion revolves around calculating the mass of iron in a 250ml glass of Milo based on its concentration measured in parts per million (ppm) and the dilution process used in atomic absorption spectroscopy (AAS). The focus includes both theoretical and practical aspects of concentration conversion and mass calculation.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a scenario involving the dilution of a Milo sample and the need to calculate the iron mass in a 250ml serving based on a concentration of 25.7ppm.
  • Another participant suggests that the problem is poorly formulated, noting that ppm is defined as mass per mass, and the mass of the sample is not provided.
  • A participant expresses uncertainty about converting ppm to mol/L and seeks guidance on how to perform this conversion.
  • Some participants argue that no conversions are necessary for the mass calculation, emphasizing that the mass of iron can be derived directly from the concentration without needing molar concentration.
  • There is a suggestion to assume the density of the Milo drink is similar to that of water for simplification in calculations.

Areas of Agreement / Disagreement

Participants express differing views on whether conversions are necessary for the calculation, with some insisting that direct mass calculations can be performed while others emphasize the need for conversions. The discussion remains unresolved regarding the best approach to take.

Contextual Notes

Participants note the assumption of water density for the Milo drink, which may affect the accuracy of the mass calculations. There is also mention of the lack of information regarding the mass of the sample in ppm calculations.

gordda
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I am having major trouble trying to figure the concentration of a substance that is given by the AAS. Here's the question:
To determine the iron content in a 'Milo' milk drink, a 5ml sample was diluted to 50ml. the absorption of the diluted solution and of several standard solution were measured using AAS.

What mass of iron would you consume by drinking 250ml glass of Milo?

It is given that the concentration of iron, in ppm, in the diluted milo is 2.57ppm hence the concentration of iron, in ppm, in the undiluted milo is 25.7ppm.

If anybody could work this out it would be greatly appreciated

Thanx:)
 
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V = 250 mL, C = 25.7 ppm - AAS doesn't mean anything here, you know the volume, you know the concetration, go ahead. The problem is that IMHO the formulation is stupid - ppm is mass of substance per mass of sample but mass of sample is not given. Assume density of water (1 g/mL).
 
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but i can't just use the formula n=cv because i need to change ppm into mol/L. and i have no idea how to do that? how do u change ppm into mol/L.
 
google: ppm concentration
 
gordda said:
but i can't just use the formula n=cv because i need to change ppm into mol/L. and i have no idea how to do that? how do u change ppm into mol/L.
Follow Borek's advice. Assume that milk has the density of water.

1 ppm means there's 1 gm of Fe in a million gms of milk. Convert the first number into moles (from the atomic wt of Fe) and the second into a volume (assuming the density as above), and you are done.
 
There is no need for any conversions! You are asked about mass of iron so you don't need molar concentration for anything.
 
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Borek said:
There is no need for any conversions! You are asked about mass of iron so you don't need molar concentration for anything.
Ummm...yes; didn't look carefully. Still need to convert volume of solution into a mass, but that's the only one.
 

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