Gravimetri Tembaga (Cu) _ Tutorial Prosedur Analisis + perhitungan

Summary

This video guides viewers through the process of determining copper content using gravimetric analysis. Key steps include preparing equipment, dissolving the copper sample, adding reagents like NaOH for precipitation, and filtering and washing the formed copper compounds. The end result is a copper-rich precipitate that is carefully dried and weighed to calculate the copper percentage in the original sample. The method involves precise laboratory techniques such as heating, filtration, and careful mass measurements to ensure accuracy. The final copper content is calculated using a specific formula.

Takeaways

• 😀 The gravimetric method is used to determine copper content in a sample by precipitating copper ions as copper oxide (CuO).
• 😀 The procedure involves careful preparation of equipment, including heating and weighing a crucible to ensure consistent mass.
• 😀 The sample is dissolved in sulfuric acid and then heated to enhance solubility before adding NaOH to precipitate copper ions.
• 😀 NaOH is added drop by drop to form a blue copper hydroxide (Cu(OH)2), which decomposes to black copper oxide (CuO) under heat.
• 😀 pH is monitored with litmus paper, and NaOH addition is stopped once the solution turns alkaline, ensuring the reaction's completeness.
• 😀 The precipitate is filtered, washed, and checked for purity using BaCl2 to test for sulfate contamination from sulfuric acid.
• 😀 The copper oxide precipitate is dried in a crucible and heated until all water is removed and the mass is stable.
• 😀 The mass of the copper oxide is measured, and the copper content in the sample is calculated using stoichiometric relations.
• 😀 The final copper content is calculated using the formula: (Mass of CuO / Mass of Sample) * (Molar Mass of Cu / Molar Mass of CuO) * 100%.
• 😀 The experiment demonstrates the precision and reliability of gravimetric analysis when conducted carefully, with an example yielding a copper content of 26.8%.

Q & A

What is the purpose of using the gravimetric method in copper content determination?

The gravimetric method is used to determine the copper content in a sample by precipitating copper as a solid compound, allowing its mass to be measured and calculated based on the sample weight.

Why is it important to preheat the crucible before weighing it?

Preheating the crucible is important to remove any residual moisture and ensure that the crucible is at a consistent temperature, preventing inaccuracies in the mass measurement.

What is the purpose of adding H2SO4 (sulfuric acid) to the copper sample solution?

H2SO4 is added to the solution to increase the solubility of the copper sample, aiding in its dissolution before further chemical reactions occur.

Why is NaOH (sodium hydroxide) added drop by drop during the experiment?

NaOH is added drop by drop to ensure the controlled formation of a precipitate, as it reacts with copper ions to form a blue copper hydroxide, which decomposes to form a black copper oxide.

What happens when the pH indicator turns from red to blue using litmus paper?

The color change from red to blue indicates that the solution has become alkaline, meaning the sodium hydroxide has sufficiently neutralized the acid, creating the right conditions for copper precipitation.

What is the significance of filtering the precipitate through filter paper?

Filtering the precipitate ensures that the solid copper compound is separated from the liquid phase, leaving only the pure copper compound for further analysis.

Why is hot water used to wash the precipitate during filtration?

Hot water is used to wash the precipitate to remove any soluble impurities, such as sulfates, ensuring that the copper precipitate is as pure as possible before it is dried and weighed.

How is the purity of the precipitate tested during the washing step?

The purity of the precipitate is tested by adding BaCl2 (barium chloride) to the washing water. If no white precipitate forms, it indicates that the copper precipitate is free from sulfate contamination.

What does the process of ignition (heating) of the sample in the crucible achieve?

The ignition process heats the sample to remove any remaining water and to convert the copper hydroxide into copper oxide, which is then weighed to calculate the copper content.

How is the final copper content calculated from the mass of the copper oxide precipitate?

The copper content is calculated using the formula: (Molar mass of Cu / Molar mass of CuO) * (Mass of CuO / Mass of sample) * 100%, which gives the percentage of copper in the original sample.