BIOLOGY LESSON NOTE ON HUMAN KIDNEY

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Lesson Note on the Human Kidney Topic: The Human Kidney Duration: 40 minutes Specific Objectives: By the end of the lesson, students should be able to: Define the kidney and state its location in the human body. Identify and describe the structure and functions of the kidney. Explain the processes involved in urine formation (filtration, reabsorption, and secretion). Describe how the kidney contributes to homeostasis. Identify common kidney-related diseases and how to prevent them. Evaluate the importance of maintaining kidney health. Lesson Content: 1. Introduction to the Human Kidney The kidneys are vital organs in the human body responsible for filtering waste from the blood and regulating water and electrolyte balance. They are part of the excretory system and play a crucial role in homeostasis. Location: The kidneys are located in the abdominal cavity, on either side of the spine, just below the rib cage. Each kidney is bean-shaped and about the size of a fi...
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Chemistry Lesson Note on Acid-Base Titration – Apparatus, Procedures, Calculations


Topic: Acid-Base Titration – Apparatus, Procedures, Calculations

Class: SS1

Specific Objectives:

By the end of this lesson, students should be able to:

  1. Define titration and state its purpose.
  2. Identify the apparatus used in acid-base titration.
  3. Describe step-by-step procedures for carrying out a titration.
  4. Record and interpret titration results.
  5. Perform basic titration calculations to determine unknown concentrations.

Instructional Materials:

  • Burette and stand
  • Pipette and pipette filler
  • Conical flask
  • White tile
  • Measuring cylinder
  • Beakers and wash bottle
  • Indicator (e.g., methyl orange or phenolphthalein)
  • Known acid (e.g., HCl) and base (e.g., NaOH) solutions
  • Laboratory notebook for recording results

Lesson Content:

Step 1: Meaning of Titration

Titration is a volumetric analytical technique used to determine the unknown concentration of a solution by reacting it with a solution of known concentration.

In acid-base titration, an acid reacts with a base in the presence of an indicator to determine the concentration of either the acid or the base.

Step 2: Apparatus Used in Titration

Apparatus Function
Burette Delivers known volume of titrant (solution of known concentration) into the conical flask.
Pipette Measures a fixed volume (usually 25 cm³) of the solution with unknown concentration.
Conical Flask Holds the unknown solution and receives the titrant during titration.
White Tile Helps observe color changes clearly.
Indicator Detects the end-point of the titration by color change.

Common Indicators:

Indicator Acid Color Base Color Suitable Titration
Methyl orange Red Yellow Strong acid vs weak base
Phenolphthalein Colorless Pink Weak acid vs strong base

Step 3: Procedure for Carrying Out Titration

  1. Rinse the burette with the standard solution (acid or base), then fill and clamp it vertically.
  2. Rinse the pipette with the unknown solution, then transfer 25 cm³ into a clean conical flask.
  3. Add a few drops of a suitable indicator into the flask.
  4. Place the flask on a white tile.
  5. Record the initial burette reading.
  6. Open the burette tap slowly to allow the standard solution to flow into the conical flask.
  7. Swirl the flask continuously to mix.
  8. Watch for the end-point (color change of indicator).
  9. Record the final burette reading and calculate the volume of titrant used (titre).
  10. Repeat the titration until you get concordant results (titres within 0.1 cm³ of each other).

Step 4: Sample Calculation

Example:
25 cm³ of NaOH neutralizes 22.5 cm³ of 0.10 mol/dm³ HCl. Find the concentration of NaOH.

Reaction:

Mole ratio = 1:1

Step-by-step:

  1. Moles of HCl:

\text{Moles} = C \times V = 0.10 \times \frac{22.5}{1000} = 0.00225 \text{ mol}

  1. Since mole ratio is 1:1, moles of NaOH = 0.00225 mol

  2. Concentration of NaOH:


C = \frac{\text{moles}}{\text{volume}} = \frac{0.00225}{25/1000} = 0.09 \text{ mol/dm}^3

Step 5: Precautions During Titration

  • Always remove air bubbles in the burette tip.
  • Ensure consistent swirling of the flask.
  • Use correct indicator for acid-base strength.
  • Take readings from the lower meniscus (especially for colorless solutions).
  • Perform multiple trials for accuracy.

Evaluation:

  1. What is the purpose of titration?
  2. List five apparatus used in acid-base titration.
  3. Why is a white tile placed under the conical flask?
  4. What is the color change observed with phenolphthalein in a base?
  5. A student used 24.0 cm³ of 0.1 mol/dm³ H₂SO₄ to neutralize 25 cm³ of NaOH. Calculate the concentration of NaOH.

Homework:

  1. Describe the step-by-step procedure for a titration involving HCl and NaOH using methyl orange.
  2. If 20.0 cm³ of 0.15 mol/dm³ HCl is required to neutralize 25.0 cm³ of NaOH, calculate the concentration of NaOH.
  3. List three common errors that may occur during titration and how to avoid them.

Conclusion:

Titration is a precise and widely used method in analytical chemistry for determining concentrations of solutions. Mastery of technique and calculations is essential for success in practical chemistry.

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