Explanation

• The statement "A chemical compound always contains the same elements combined together in the same proportion or ratio" is a statement of the Law of Constant Composition.
• It is also known as the Law of Definite Proportions.
• This law was first discovered by Joseph Proust in 1797.

Explanation

• Iodine-123 is used for the diagnosis of thyroid gland function.
• It is a radioactive isotope that helps in imaging and evaluating the performance of the thyroid gland.

Explanation

• When an atom gains or loses electrons, it becomes an ion.
• If it gains electrons, it becomes a negative ion (anion).
• It it loses electrons, it becomes a positive ion (cation).

Explanation

The substitution of a hydrogen atom (−H) by a nitro group (−NO2) on a benzene ring is called nitration.

Nitration is typically carried out using concentrated nitric acid (HNO3) and sulfuric acid (H2SO4).

The sulfuric acid acts as a catalyst and generates the nitronium ion (NO2+), the electrophile that reacts with the benzene ring.

The overall reaction can be represented as:

C6H6 + HNO 3 → C 6H5NO2 +H2O

Here, benzene (C6H6) is converted to nitrobenzene (C6H5NO2).

This is a key reaction in organic chemistry, especially in the synthesis of various aromatic compounds.

Explanation

• Common Salt (NaCl) is a compound, not a mixture.
• It is a pure substance made up of sodium and chlorine atoms in a fixed ratio.

Explanation

In a solid, the particles are arranged in a regular and closely packed manner, with a fixed position and shape.

Explanation

• A solid is a state of matter that has a fixed shape and a fixed volume.
• Solids maintain their shape and volume unless an external force is applied to change them.
• Liquid: A liquid has a fixed volume but takes the shape of its container.
• Gas: A gas has neither a fixed shape nor a fixed volume. It expands to fill its container.

Explanation

• Stoichiometry is a term derived from the Greek words "stoicheion" (element) and "metron" (measure).
• It refers to the study of the quantitative relationships between reactants and products in chemical reactions, and is a fundamental concept in chemistry.

Explanation

Amines are of three types, primary, secondary and tertiory.

1. Primary amines are those which directlr attached to one carbon as CH3NH2 or RNH2.
2. Secondary amines are those which attached to two more carbon atoms as C2H5 − NH − C2H5 or R2NH
3. Tertiory amines all valency of nitrogen are satisfied by alkyl groupe R3N.

Explanation

• Dry ice is the solid form of carbon dioxide (CO2), and it is an example of a molecular crystal.
• In a molecular crystal, the molecules are held together by weak intermolecular forces such as van der Waals forces or hydrogen bonds, rather than by strong chemical bonds.