Experiment 3 Corrosion of Metals

Summary

The experiment focuses on the corrosion of metals, starting with testing metal reactions in various aqueous solutions. Clean iron nails are immersed in solutions like HCl, NaOH, NaCl, and water to observe corrosion after 24 hours. Potassium ferricyanide is added to identify the presence of ferrous ions. The experiment includes preparing an agar medium to investigate the effects of mechanical stress on iron corrosion and the interaction between different metals (iron, copper, zinc). Observations are recorded, and the procedures demonstrate the impact of acidity, metal combinations, and stress on corrosion.

Takeaways

• 🛠️ Clean the nails using sandpaper to ensure they are bright before starting the experiment.
• 🧪 Place a clean, bright nail in each of the five test tubes and ensure the nails are immersed in solutions like 0.1M HCl, NaOH, NaCl, and distilled water.
• 🔬 Label the test tubes and determine the acidity of the solutions using litmus paper, noting color changes to assess acidity, basicity, or neutrality.
• ⏳ Allow the nails to stand overnight, and observe the changes in both the nails and the solutions after 24 hours.
• 🧊 Add 1-2 drops of 0.1M potassium ferricyanide to the solutions and record any color changes to detect ferrous ion formation.
• 🧪 Prepare a new test tube with potassium ferricyanide and ferrous sulfate to observe reactions with ferrous ions.
• 📊 Record the observations of corrosion in the provided tables, focusing on which setups promote oxidation and corrosion of iron.
• 🔥 Boil distilled water, add agar, potassium ferricyanide, and phenolphthalein to create an agar medium for testing mechanical stress's effect on corrosion.
• 🔧 Place a straight nail and a bent nail in the prepared agar medium and observe any color changes after 24 hours to study mechanical stress effects.
• ⚡ Test the corrosion by winding copper and zinc strips around clean iron nails and placing them in the agar medium to observe reactions between the metals.

Q & A

What is the first step in preparing the nails for Experiment 3: Corrosion of Metals?

The first step is to clean the nails using sandpaper until they are bright and free of dirt or rust.

How should the nails be placed in the test tubes to avoid breaking the test tubes?

The nails should be carefully slid down the side of each test tube to avoid breaking the bottom.

What solutions are used to immerse the nails in the test tubes, and why is it important to label them?

The solutions used are 0.1M HCl, 0.1M NaOH, 0.1M NaCl, and distilled water. Proper labeling ensures that the results can be accurately recorded for each solution.

How do you determine the acidity of each solution, and what should you note down?

The acidity of each solution is determined using litmus paper. A blue litmus paper turning red indicates an acidic solution, a red litmus paper turning blue indicates a basic solution, and no color change indicates a neutral solution. Record the results in Table 3.1 in the data sheet.

What is the purpose of leaving one nail unimmersed in any solution, and what is this setup called?

One nail is left unimmersed to act as a control setup. This allows comparison to see if corrosion occurs only in the solutions.

After 24 hours, what observations should be made regarding the nails and the solutions?

The changes in both the nails and the solutions should be observed. These observations, including signs of corrosion, are recorded in Table 3.1 of the data sheet.

What happens when 1-2 drops of 0.1M potassium ferricyanide solution are added to the test tubes, and why is this important?

A color change will occur when potassium ferricyanide reacts with ferrous ions. Observing this change helps determine whether corrosion, which produces ferrous ions, has taken place.

What does potassium ferricyanide indicate when added to ferrous sulfate, and what should be recorded?

Potassium ferricyanide reacts with ferrous ions to form a color change. The reaction is recorded in Table 3.2, showing where ferrous ions were present.

What role does phenolphthalein play in the experiment, and how does it indicate the pH of the environment?

Phenolphthalein changes color based on pH. It is colorless in acidic environments and pink in basic environments, indicating the pH around the nails.

What is the purpose of winding copper and zinc strips around iron nails in the experiment?

The purpose is to observe how contact with different metals (copper or zinc) affects the corrosion of the iron nail. The setup is used to study galvanic corrosion and its influence on iron.