Ijmb Model Questions Vol1 2025 Chemistry Question 4

Practice practical question 4 from the 2025 Ijmb Model Questions Vol1 Chemistry examination. This question covers Mole Concept .

Ijmb Model Questions Vol1 2025 Chemistry Practical
Topic: Mole Concept
Question 4 IJMB_MODEL_QUESTIONS_VOL1 • 2025 • CHEMISTRY • practical

A sample of impure calcium carbonate (CaCO₃) was analysed gravimetrically to determine its percent purity. Procedure (summarised): 1. A 1.250 g portion of the impure solid was weighed into a crucible. 2. The sample was treated with excess dilute H₂SO₄ to convert all CaCO₃ to calcium oxalate, which was then filtered, washed and dried. 3. The calcium oxalate precipitate was ignited in a muffle furnace at 900 °C until a constant mass was obtained. The product of ignition is calcium oxide (CaO). 4. After cooling in a desiccator, the mass of CaO was recorded as 0.560 g. Using the data above, answer the following questions.

Question Parts

( a )
Write the balanced chemical equation for the thermal decomposition of calcium carbonate to calcium oxide.
( b )
Calculate the number of moles of CaO obtained from the sample.
( c )
From the moles of CaO, determine the theoretical mass of CaCO₃ that would have been present in the original sample.
( d )
Calculate the percent purity of the impure CaCO₃ sample.
( e )
State two possible sources of error that could affect the accuracy of the percent purity obtained.
( f )
Suggest one improvement to the experimental procedure that would minimise the errors identified in part (e).

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About This Question

This is Ijmb Model Questions Vol1 2025 Chemistry Question 4. It is one of the practical questions from the 2025 Ijmb Model Questions Vol1 Chemistry examination.

The question covers Mole Concept .

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