Why does every sample of given substance has the same properties?

Apure solvent has a vapor pressure the vapor pressure of a solution. a. equal to b. lower than c. higher than

The chemical bond connecting one nucleotide with the next one along the nucleic acid chain is called a

The chemical equation below shows the reaction of sodium (na) and chlorine (cl) to form sodium chloride (nacl). 2na + cl2 → 2nacl in this equation, which of the following is a reactant? i. sodium ii. chlorine iii. sodium chloride