The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser. Step 1 Fertiliser weighed Dissolved + filtered + rinsed Residue discarded Step 2 Filtrate Addition of Ba^{2+} Step 3 Precipitation Filtered Filtrate discarded Step 4 Rinsed Dried and weighed (a) What assumptions were made and how do these affect the validity of this process? (b) It was found that 4.25 g had a sulfate content of 35%. What is the mass of the dried precipitate at Step 4? Include a chemical equation in your answer.

SSCE HSC Chemistry Analysis of Inorganic Substances: The flowchart shown outlines the

The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser - HSC - SSCE Chemistry - Question 29 - 2010 - Paper 1

Question 29

The-flowchart-shown-outlines-the-process-used-to-determine-the-amount-of-sulfate-present-in-a-sample-of-lawn-fertiliser-HSC-SSCE Chemistry-Question 29-2010-Paper 1.png

The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser. Step 1 Fertiliser weighed Dissolved + filte... show full transcript

Worked Solution & Example Answer:The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser - HSC - SSCE Chemistry - Question 29 - 2010 - Paper 1

Step 1

What assumptions were made and how do these affect the validity of this process?

96%

114 rated

Answer

Several assumptions are made in this process. Firstly, it is assumed that all sulfate ions in the fertiliser dissolve completely in the dissolving step. This assumption affects validity because incomplete dissolution could lead to an underestimate of the sulfate content.

Secondly, it is presumed that the addition of Ba^{2+} ions will precipitate all sulfate ions as barium sulfate (BaSO₄). If some sulfate ions remain unreacted, it could lead to discrepancies in the final mass measured.

Lastly, proper washing of the precipitate is assumed to remove any impurities. If not done effectively, the presence of impurities could affect the weight of the dried precipitate, skewing the results.

Step 2

What is the mass of the dried precipitate at Step 4? Include a chemical equation in your answer.

99%

104 rated

Answer

To find the mass of the dried precipitate at Step 4, we start by calculating the mass of sulfate in the original sample.

Given that the sulfate content is 35%, the mass of sulfate (m_{SO₄}) in 4.25 g can be calculated as:

$m_{SO₄} = 0.35 imes 4.25 ext{ g} = 1.4875 ext{ g}$

The chemical equation for the precipitation reaction is:

$ext{Ba}^{2+} + ext{SO}_{4}^{2-} \rightarrow ext{BaSO}_{4} \downarrow$

Thus, the mass of the dried precipitate at Step 4, which is barium sulfate, is equal to the mass of sulfate present since all sulfate reacts to form the precipitate.

The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser - HSC - SSCE Chemistry - Question 29 - 2010 - Paper 1

Worked Solution & Example Answer:The flowchart shown outlines the process used to determine the amount of sulfate present in a sample of lawn fertiliser - HSC - SSCE Chemistry - Question 29 - 2010 - Paper 1

What assumptions were made and how do these affect the validity of this process?

What is the mass of the dried precipitate at Step 4? Include a chemical equation in your answer.

Join the SSCE students using SimpleStudy...