B3+ is isoelectronic with helium.
Isoelectronicity is the phenomenon whereby two or more molecular entities have the same number of electrons or similar electronic configuration regardless of the nature of the elements that are involved.
In the question given above, helium and B3+ have the same number of electrons. Helium has two electrons. Boron has five electrons but it has given away three of the electrons [that is why it has a charge of +3] and it now has only two left.
Base on your question where a concentration cell consist of two SN/SN2+half cells. The solution in one half cell A is 0.13M SN(NO3)2 and is 0.87 M Sn(NO3)2 in the other half cell to get the cell potential at 25 degree the answer is 0.059/2 log0.13/0.87
Answer:
3.711 L
Explanation:
The formula you need to use is the following:

3.4L / 298 K = V2 / 273 K
V2 = 3.711 L
The correct answer is option B. X-rays are the waves found in the electromagnetic spectrum at a wavelength of 1x10^-11 - 1x10^-8 m and frequencies of 3x10^16 to 3x10^19 Hz. These waves penetrate easily through certain materials which made them usefule in the field of medicine.