Chemistry

Acyl chloride is hydrogenated over catalyst, palladium or barium sulphate. This reaction is called Rosenmund reaction.

The inertness of ? subshell electrons towards bond formation is known as inert pair effect. This effect increases down the group thus, for Sn,  oxidation state is more stable, whereas, for Pb,  oxidation state is more stable, i.e.,  is reducing while  is oxidising.

Sodium carbonate is a white crystalline solid which exists as a decahydrate,  This is also called washing soda.

Due to its high dielectric constant, water is a good solvent.

Bond angles give some idea regarding the distribution of orbitals around the central atom in a molecule/complex ion and hence it helps us in determining its shape

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When any change in matter is not responsible for changing the characteristic of the reaction,   the amount of matter we would have intensive properties. These properties, which we know as temperature or density,   remain constant even when the matter's size or quantity changes. On the other hand, we would have extensive properties in substances when they change when the amount or quantity in the system changes. 

Internal energy is the sum of all the energy in the system, as simple as that. But if we look into enthalpy, it is a state function that tells us how much internal energy is there in the system and how much work would be required to do to expand a gas against a constant pressure.