Explain why some nuclei cannot experience magnetic resonance and give two examples.

Any nucleus that has an overall spin quantum number of zero (I=0) is NMR inactive

Explanation:

A wide range of nuclei are found to be NMR active. NMR is the acronym for nuclear magnetic resonance. It is a powerful spectroscopic tool which uses radio waves. The nuclear spin is described by the nuclear quantum number I and can take on values of; 0,1/2, 1, 3/2,2,5/2 etc.

Any nucleus that has an overall spin quantum number of zero (I=0) is NMR inactive e.g Carbon-12 and Oxygen-16 nuclei.

Commonly, all NMR active nuclei posses I ≥ 1/2, Hydrogen -1 , Carbon-13 and boron-11 are common examples of NMR active nuclei.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.