Explain why eating a meal with too much salt leads to production of small volume of concentrated urine.

Eating a meal with too much salt leads to a decrease in the water potential of blood. This fall in water potential is detected by the osmoreceptors in the hypothalamus (in brain). The hypothalamus stimulates the pituitary gland to release antidiuretic hormone (ADH). The walls of the collecting duct in the kidney become more permeable to water, hence, a greater proportion of water is reabsorbed from the urine back into the blood by osmosis.

As a result, a small volume of concentrated urine is formed.

b.have there own function.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.