Gravimetric Analysis Homework: Mass % of Barium Ions in Mixture

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In summary, the mass percent of barium ions in the impure mixture is 4.79%. This was determined by first calculating the molar ratio between barium and barium sulfate, which is 1:1. Then, using the mass of dried barium sulfate obtained (0.408g), the mass of barium ions in the mixture was calculated to be 0.0828g. This was then divided by the initial mass of the mixture (1.728g) and multiplied by 100 to obtain the mass percent. Although it is not necessary, converting to moles and back to masses also yielded the same result.
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leah3000
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Homework Statement


An aqueous solution containing 1.728g of an impure mixture was analysed for barium ions by adding sufficient sulphuric acid solution to completely precipitate the barium ions as its sulphate. The precipitate was filtered, washed and dried to constant mass and finally weighed. What is the mass percent of barium ions in the mixture, if 0.408g of dried barium sulphate was obtained?


Homework Equations



I used this as the balanced equation but somehow it looks funny to me...

BaX + H2SO4 ------> BaSO4 + HX
1.728g 0.1408g

The Attempt at a Solution



no of mols BaSO4 produced = mass/Mr

Mr of BaSo4= (137.3)+ (32.1) + (16x4)
= 233.4

mols= 0.1408/233.4
=6.033x10^-4

BaX : BaSO4
1 : 1

mass Ba^2+ = molsx Mr
=(6.033x10^-4) x 137.3
=0.0828g

% of Ba^2+ present in mixture= (0.0828/1.728) x100
= 4.79%

Am i on the right track? Plz help!
 
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  • #2
Hi leah3000! :smile:

You are very much on the right track!

Only one thing: you seem to have made a typo followed by the corresponding calculation errors when you wrote 0.1480 instead of 0.480.
 
  • #3
oops. thanks for the help
 
  • #4
The only thing that matters is that molar ratio between barium and barium sulfate is 1:1. This is enough to solve the problem.

Also note that while it is perfectly correct to convert everything to moles and back to masses, it is not necessary. See stoichiometric calculations using ratios for details.
 
  • #5


Your calculations and approach seem to be correct. However, it is always a good idea to double check your work and make sure your units are consistent throughout your calculations. Additionally, make sure to label your final answer with the appropriate units (%). Overall, it appears that you have successfully calculated the mass percent of barium ions in the mixture. Great job!
 

1. How is gravimetric analysis used to determine the mass % of barium ions in a mixture?

Gravimetric analysis is a quantitative analytical method that involves the separation and determination of a specific compound or element in a mixture based on its mass. In the case of determining the mass % of barium ions in a mixture, the sample is first dissolved in a solution and then reacted with a known reagent that will produce a solid barium compound. The precipitate is then filtered, dried, and weighed to determine the mass of barium. This mass is then used to calculate the mass % of barium ions in the original mixture.

2. What precautions should be taken during gravimetric analysis to ensure accurate results?

Some precautions that should be taken during gravimetric analysis include ensuring that all equipment and glassware are clean and free of any contaminants, using accurate and precise measurements, and performing multiple trials to ensure reproducibility of results. It is also important to follow the specific procedure and technique recommended for the analysis to ensure accurate and reliable results.

3. Can gravimetric analysis be used to determine the mass % of barium ions in a mixture of other elements?

Yes, gravimetric analysis can be used to determine the mass % of barium ions in a mixture of other elements. However, the specific procedure and reagents used may vary depending on the other elements present in the mixture. It is important to carefully select the appropriate reagents and follow the recommended procedure to ensure accurate results.

4. What are some potential sources of error in gravimetric analysis?

Some potential sources of error in gravimetric analysis include incomplete precipitation, loss of precipitate during filtration, contamination of the sample or reagents, and errors in measurement or calculation. It is important to carefully control and monitor these potential sources of error to ensure accurate and reliable results.

5. How can the mass % of barium ions in a mixture be used to determine the purity of a sample?

The mass % of barium ions in a mixture can be used to determine the purity of a sample by comparing it to the expected or theoretical mass % of barium ions in a pure sample. If the calculated mass % is significantly lower than the expected value, it may indicate impurities in the sample. However, it is important to consider other factors, such as sources of error, before making any conclusions about the purity of the sample based on gravimetric analysis results.

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