# Finding concentration of a sample

• AMan24
In summary: I don't see what the 25 ml has to do with the answer.I don't think your teacher was giving you a trick question here but if you give us all the information in the question we can help you out.
AMan24

## Homework Statement

1.02 grams of an unknown sample, that contains iron and some other things. Amount of iron is unknown, other substances are unknown.

The concentration is 0.023 mg Fe/mL

The question says find the mass of Fe (in mg) in the 1.02 gram sample.

Exact question is:
"The unknown iron solution in the 25 mL volumetric flask was the result of pipeting 3.00 mL from the 1000.00 mL flask which originally contained the entire dissolved sample. Use principles of dilution and concentration to find the mass in milligrams of iron present in the 1.00 liter volumetric flask. This is the amount present in the original dry sample."

The concentration i gave was for the 25 mL

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none.

## The Attempt at a Solution

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I'm guessing i have to convert from the concentration, to molarity, and go to grams divide by molar mass, something like that. I think it will be something similar to that. I will update the attempt because its not really clear right now.

Last edited:
AMan24 said:
The concentration is 0.023 mg Fe/mL
ml of what? Is the substance dissolved somewhere? If it is a solid, you still need the density or something similar you use that value.

mfb said:
ml of what? Is the substance dissolved somewhere? If it is a solid, you still need the density or something similar you use that value.
These are the exact directions. I seriously have no idea how to do this. We weren't taught this.

"The unknown iron solution in the 25 mL volumetric flask was the result of pipeting 3.00 mL from the 1000.00 mL flask which originally contained the entire dissolved sample. Use principles of dilution and concentration to find the mass in milligrams of iron present in the 1.00 liter volumetric flask. This is the amount present in the original dry sample."

The concentration i gave was for the 25 mL

Why didn't you include that part in the original version of the first post? The question does not make sense without that part.

AMan24 said:
The concentration i gave was for the 25 mL
If you have 25 ml of 0.023 mg Fe/ml, how much iron do you have in that 25 ml?

It sounds like he only has 3ml in the the flask that can hold 25ml.

Where did you get the concentration and 1.02grams from? It's not it the "exact question".

But if the concentration is correct then just multiply it with the ml of solution in the 1L flask. By the way you don't say how much solution there is in the 1L flask.

I don't think your teacher was giving you a trick question here but if you give us all the information in the question we can help you out.

MullaTheMech said:
It sounds like he only has 3ml in the the flask that can hold 25ml.
Where would be the point of the 25 ml thing then? There would also be no reason to take 3 ml, and the reference to dilution would not make sense.

I'm quite sure the 3 ml get diluted in the 25 ml flask.

AMan24

## What is the purpose of finding the concentration of a sample?

The concentration of a sample is the amount of a particular substance present in a given volume of a solution. It is an important measurement in many scientific fields, as it can provide information about the purity, strength, and effectiveness of a substance.

## How is the concentration of a sample determined?

The concentration of a sample can be determined through various methods, such as titration, spectrophotometry, and gravimetric analysis. These methods involve measuring the amount of a substance in a solution and calculating its concentration based on known equations and principles.

## What are the units of concentration?

The units of concentration can vary depending on the method used to determine it. Some common units include molarity (M), moles per liter (mol/L), parts per million (ppm), and percent (%). It is important to note the units when reporting concentration to ensure accurate communication of data.

## Why is it important to accurately determine the concentration of a sample?

The concentration of a sample is a crucial aspect in many scientific experiments and applications. It can affect the outcome and validity of results, as well as the safety and effectiveness of products. Accurate determination of concentration allows for better understanding and control of chemical reactions and processes.

## What are some factors that can affect the accuracy of concentration measurements?

There are several factors that can affect the accuracy of concentration measurements, such as human error, contamination, improper calibration of equipment, and variations in the sample. It is important to follow proper procedures and use reliable methods to minimize these factors and ensure accurate results.

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