Practical No. 09: Preparation of Corrosive Medium for Aluminium
XIII. Interpretation of Results
Normal solutions of HCl, H₂SO₄, HNO₃, and NaOH were successfully prepared using normality formula N₁V₁ = N₂V₂. Calculated volumes from concentrated acids/bases were accurately determined for desired normality.
XIV. Conclusions and Recommendations
- Conclusion: Corrosive media of desired concentrations can be prepared using normality equation.
- Recommendation: Always add acid to water (never water to acid) with stirring, wear safety equipment, and label all solutions properly.
XV. Practical Related Questions & Answers
Q1. Mention the type of corrosion takes place when metal comes in contact with acids/base.
- Answer: When metal comes in contact with acids/bases, Wet corrosion (also called Electrochemical corrosion) takes place. In acidic medium, hydrogen gas is liberated, and the metal dissolves forming metal salts. In alkaline medium, metals like aluminium dissolve forming metal aluminates. This type of corrosion is due to the electrochemical reaction at the metal surface.
Q2. State the precaution taken for preparation of dilute acids/base.
- Answer: Precautions include:
- (i) Always add acid to water (never add water to concentrated acid) to prevent splashing.
- (ii) Use safety goggles and gloves.
- (iii) Stir continuously while adding acid.
- (iv) Use proper glassware and handle carefully.
- (v) Work in a well-ventilated area.
- (vi) Prepare solution in a heat-resistant glass beaker as dilution generates heat.
Q3. Prepare 250 ml of 2 N HCl from the given 10 N HCl.
- Answer:
- Formula: N₁V₁ = N₂V₂
- Given: N₁ = 10 N, N₂ = 2 N, V₂ = 250 ml
- Calculation:
V₁ = (N₂ × V₂) / N₁
V₁ = (2 × 250) / 10
V₁ = 50 ml - Conclusion: Therefore, take 50 ml of 10 N HCl and make the volume up to 250 ml by adding distilled water slowly with constant stirring.
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