Explanation:
21. The given molecule for cracking is tetradecane.
On cracking it forms one mole of decane (C10H22) and two moles of ethene gas.
The chemical equation is shown below:

22. The essential condition for the formation of an ester is the reaction of alcohol and acid in presence of concentrated sulfuric acid.
Thus among the given options, the first option is the correct one.
23. Isomers of butanol are shown below:
It is 2-butanol.
The position of -OH group changes to the second carbon.
If the states of matter have changed such as from solid to liquid, you have to remove or add energy.
Answer:
In the shell...
Explanation:
In the electronic shell, or the orbit..
Bohr's Atomic Model was given by Niels Bohr. He proposed that the electrons inside an atom moved around in orbits or shells. There were different shells in the atom named as K, L, M, N... These were also called energy levels...
Answer - Inter-molecular attractions
Explanation-
As we know everything around us is made up of matter that means everything has molecules as their basic structure. The state of anything is decided by the spaces between the molecules.
The state of the objects that have strong inter-molecular attractions a solid and gradually the lesser will be in state of liquid and gas. The attraction between the molecules is overcome only when a certain amount of energy is provided from outside.
Answer:
(b) matter is lost and energy is released
Explanation:
When atoms are being formed from its constituent components it weighs less this is called mass defect so the answer would be (b) matter is lost and energy is released.