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An experiment is carried out to determine the Ksp value for lithium phosphate (Li3PO4) - HSC - SSCE Chemistry - Question 27 - 2021 - Paper 1
Question 27
An experiment is carried out to determine the Ksp value for lithium phosphate (Li3PO4). Five samples of Li+ ion solution were prepared, and a different solution of P... show full transcript
Worked Solution & Example Answer:An experiment is carried out to determine the Ksp value for lithium phosphate (Li3PO4) - HSC - SSCE Chemistry - Question 27 - 2021 - Paper 1
Step 1
Calculate the range within which the Ksp value of lithium phosphate lies.
Answer
To determine the Ksp value for lithium phosphate, we start with the formula:
Using the data from the samples:
Sample 3 (no precipitate):
- [Li^+] = 0.15 mol L^-1
- [PO4^3-] = 0.010 mol L^-1
Calculating Ksp: This value can be rounded to:
ightarrow 0.00034 ext{ (to 2 significant figures)} $$ Sample 4 (precipitate present): - [Li^+] = 0.15 mol L^-1 - [PO4^3-] = 0.10 mol L^-1 Calculating Ksp: $$ K_{sp} = (0.15)^3 imes (0.10) = 0.0003375 $$ This value rounded will be: $$ K_{sp} ext{ (Sample 4)} ightarrow 0.00034 ext{ (to 2 significant figures)} $$ Thus, the Ksp value lies between the calculated values for sample 3 and sample 4. Therefore, the range within which the Ksp value lies is: $$ 3.4 imes 10^{-5} < K_{sp} < 3.4 imes 10^{-4} $$Step 2
Justify ONE way in which the procedure of this investigation could be improved to increase the accuracy of the calculated result.
Answer
One way to improve the investigation's accuracy is to minimize the concentration range of the solutions of ions. By decreasing the concentration range to 0.010 mol L^-1 to 0.10 mol L^-1, this would narrow the results and refine the estimated value closer to the SI value of lithium phosphate.