Questions and Answers
What is the primary reason for ensuring a balance is located on a hard, stable, level surface?
What should be done before using any laboratory balance?
Which type of balance typically offers milligram accuracy and is popular in laboratories today?
What is the correct method to fill pipettes safely?
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Why is using a lightweight weighing container recommended when using a balance?
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What type of glassware is essential for the preparation of culture media?
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Which method provides the most precise measurements when preparing solutions?
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What is a common mistake when measuring liquids with graduated cylinders?
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How does the third type of pipettor operate?
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Which of the following statements is true regarding the reading of a meniscus in calibrated equipment?
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What type of glassware is least suitable for precise measurements of liquid volume?
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Why should a clean graduated cylinder always be used for measurement?
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What is the shape of the meniscus formed by aqueous solutions in glassware?
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What calibration method minimizes errors in noting the level of the meniscus?
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Which factor primarily contributes to improper drainage of liquid in a graduated cylinder?
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Which equipment is designed specifically to deliver a certain specific volume of liquid accurately?
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Study Notes
Basic Laboratory Techniques
- In vitro plant propagation requires familiarity with laboratory operations focusing on accuracy, cleanliness, and attention to detail.
- Careful weighing of media components is crucial for preparation, even when using commercially prepared mediums.
Weighing Techniques
- Various laboratory balances include:
- Top-loading single-pan balance
- Triple-beam balance
- Double-pan torsion balance
- Analytical single-pan balance
- Top-loading electronic balance (noted for accuracy and ease of use)
- Top-loading electronic balances can achieve milligram accuracy which was once exclusive to analytical balances.
- Precautions for accurate weighing:
- Place balance on a stable, hard surface free from vibrations and drafts.
- Ensure cleanliness of the balance and weigh area.
- Avoid overloading the balance according to manufacturer specifications.
- Use lightweight containers for weighing instead of placing materials directly on the balance pan.
Measuring Liquids
- Calibrated glassware is essential for preparing culture media, including beakers, flasks, and pipettes.
- Graduated cylinders (10ml to 1000ml) and volumetric flasks are used for precise measurements.
- Correct reading methods include:
- Aligning the bottom of the air-liquid interface with the measuring mark to ensure accuracy.
- Pipettes must be filled using a hand-operated device (pipettor) due to safety concerns (never pipette by mouth).
Types of Pipettors
- Bulb-type pipettor: Controlled by valves.
- Wheel-operated pipettor: Rotating the wheel creates suction for filling; opposite direction releases liquid.
- Electric air pump pipettor: Draws liquid by pressing a button and releases by pressing another button.
Volume Measurement Specifics
- Volumetric flasks, graduated cylinders, pipettes, and burettes measure liquid volume.
- Calibration marks are typically etched on equipment to signify specific volumes at a designated temperature.
- Aqueous solutions form a concave meniscus; measurements should align the bottom of the meniscus at eye level with the etched mark to avoid parallax errors.
Graduated Cylinder Usage
- Always ensure the graduated cylinder is clean to avoid chemical contamination and inaccurate volume determination.
- Dirty glassware may not drain correctly, affecting measured volume.
- Graduated cylinders are available in various capacities (5mL, 10mL, 25mL, 100mL, 250mL, 500mL, 1000mL, and 2000mL).
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Description
This quiz focuses on essential laboratory techniques crucial for in vitro plant propagation. Key topics include accurate weighing methods with various types of balances and best practices for maintaining a clean and efficient work environment. Test your knowledge on the importance of precision in laboratory operations.
