You are using a 10 mL Volumetric Flask to prepare a diluted solution of dye. After transferring the 2 mL of dye solution into the flask, you can make up the solution to 10 mL by:

Question

BlackTom AI · Accepted Answer

Volumetric flasks are calibrated to contain a precise volume when the liquid meniscus exactly aligns with the calibration mark; for aqueous solutions this is read at the bottom of the concave meniscus at eye level. Surface tension causes a concave meniscus for water-based solutions, so the correct optical reference is the lowest point of that curve.

Step-by-step reasoning:
1) Relevant concepts: volumetric flasks are high-accuracy “to contain” instruments; final volume must be adjusted slowly and read at eye level. For water-like liquids, read the bottom of the meniscus. Large repetitive pipetting increases cumulative error and is awkward for fine final adjustment.
2) After transferring the 2.00 mL sample, you need ~8.00 mL of solvent to reach 10.00 mL. Add most of that bulk volume with a beaker, wash bottle, or larger pipette, but leave the last few drops to add slowly.
3) Use a dropper (or a wash bottle with care) to add the last drops: bring the meniscus up slowly until the bottom of the meniscus just touches the calibration line. Ensure your eye is level with the mark to avoid parallax error.
4) Mix by inverting the flask several times (with stopper) to homogenize the solution.

Why the correct option is correct:
- A dropper allows controlled addition of the final small volume so the meniscus can be positioned precisely; reading the bottom of the meniscus is the standard convention for aqueous solutions in volumetric glassware.

Why the other options are incorrect:
- Stopping when the top of the meniscus touches the line is wrong because you must read the bottom of a concave meniscus for water; using the top would give an incorrectly high volume.
- Using a P1000 to deliver eight 1000 μL aliquots is poor practice: repeated transfers increase cumulative volumetric error and make fine adjustment to the mark impractical; an autopipette is not ideal for the final precision fill to a volumetric flask mark.

Conclusion: therefore the correct practice is using a plastic dropper pipette and stopping once the bottom of the water meniscus touches the mark, matching the provided answer.

You are using a 10 mL Volumetric Flask to prepare a diluted solution of dye. After transferring the 2 mL of dye solution into the flask, you can make up the solution to 10 mL by:多项选择题

类似问题

You are being interviewed for a high paying laboratory position. Your final interview question is this. "Explain in detail how you would go about preparing 1.00L of a 1.00 M solution of sodium chloride."

What was the world's first widely adopted biodiversity policy?

The aim of the Paris Agreement is to ensure that the earth’s preindustrial temperature is not exceeded by more than º Celsius.

The IPCC's mission is to Blank ______.

Why have most international agreements for environmental protection been based on the honor system?

As was exhibited with the Montreal Protocol and the encouragement of reduced CFC production, trade can be an effective tool to compel compliance with international treaties.

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单