Which of the following isotopes are NMR inactive? a. 1H
b. 12C
c. 15N
d. 16o
e. 19F
f. 31P

12C and 16O

Explanation:

Here, we want to select which of the options are NMR inactive. For an isotope to be NMR inactive, then the net nuclear spin is zero.

What this means is that the number of proton present coupled with the number of neutrons are an even number pair.

What we are saying here is that the number of protons is an even number while the number of neutrons too is an even number. So the net nuclear spin in this case is zero.

in the case of oxygen, we have 8 protons and 8 neutrons. This makes the nuclear spin zero and consequently makes the isotope NMR inactive.

Same is in the case of carbon. There are 6 protons and 6 neutrons and this also makes nuclear spin zero .

In all the other isotopes in the question, we have odd number even number or even number odd number pairs of protons and neutrons.

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.

there is none because earth is stationary and flat.