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#laboratory

2 public questions tagged with this topic.

CHEMISTRY

In Lassaigne’s test, the formation of a blood-red color indicates the presence of which elements together?

When nitrogen and sulphur are present, they form NaSCN, which reacts with FeCl₃ to produce a blood-red Fe(SCN)3 . This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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Water and Mole Concept

Which method is commonly used for preparing a solution of known concentration?

Serial dilution is the accurate answer because it correctly identifies the biological function or role described in this question. In Water and Mole Concept, understanding the specific functions of molecules, enzymes, or structures is fundamental. Serial dilution fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Direct weighing, Titration, and Precipitation) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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