Some Basic Concepts Of Chemistry

Answer (a)

The option ( d) is false as -electrons do not filled monotonically with the increase in atomic number.

- Extensive properties depend on the amount or size of the substance, and they change as the size of the system changes. Examples include mass, volume, and internal energy.
- Molar volume is an extensive property because it depends on the amount of substance present.
- Internal energy is also an extensive property because it depends on the quantity of the system.
- Temperature is an intensive property because it does not change with the amount of substance.
- Density is an intensive property because it is independent of the amount of substance.
- Pressure is an intensive property because it does not depend on the amount of substance in the system.
Thus, the correct answer is Internal energy (B), as it is an extensive property.

Actinoids (or actinides) are a series of elements that include thorium, uranium, and other elements. They are known for being highly reactive, especially the lighter actinides like thorium and uranium. - (a) Actinoids are least reactive is incorrect because actinoids, especially those with lower atomic numbers, are very reactive. For instance, uranium and thorium are highly reactive and can form compounds with many elements. - (b) Does not react with HCl: This is true for some actinides. For example, thorium reacts with hydrochloric acid to form thorium chloride (ThCl ). - (c) Does not react with HNO : This is also incorrect. Many actinides, including uranium, react with nitric acid (HNO ) to form various uranium compounds. Therefore, the incorrect statement is that actinoids are least reactive.

When a shell in projectile motion explodes, the center of mass of the shell and the resulting fragments continues to follow the same trajectory as if it had not exploded. This is a result of the conservation of momentum. The center of mass will follow the same parabolic path as the projectile would have if it had not exploded. Thus, the trajectory of the center of the fragments is a parabola.