Chlorine is an element of Atomic Number 17. It is a mixture of two isotopes having a mass number of 35 and 37.
If molten magnesium chloride is electrolysed suggest a suitable electrode [anode].
P.S. - Answer given is carbon. My question is why is it carbon?
Answers
I think there is a misconception of what the atomic mass related to the atomic number means. In the periodic system of the chemical elements, one element differs from another element by the number of protons in the nucleus of each elements atom. In other words the atomic number equals the number of protons of an element. And because an atom as a whole has no charge, the positive charge of the protons has to be neutralized by the exact same number of negatively charged electrons, which in the case of chlorine is 17. In this example chlorine with the atomic number 17 has 17 positively charged protons and 17 electrons in order to be without charge as a whole atom. By definition 1 proton has the mass of 1 u, where "u" stands for unified atomic mass unit, where 1 u actually stands for the weight of about 1.661*10^-27 kg in SI units. Because this is not very handy to calculate with it is defined as 1 u.
Now back to your question. As you mentioned in your question, chlorine has the atomic mass of 35.45 u. Why not 17, and why such an uneven number? In the nucleus of every atom (except hydrogen) there are not only protons but also neutrons, which have the same mass like protons but possess no charge, as the name suggests. Atoms of the same element can have different numbers of neutrons, and this different subspecies of one element are called isotopes. Some isotopes of an element are stable and other isotopes are not and undergo radioactive decay. Most elements found in nature are stable isotopes, but e.g. uranium is a radioactive element with only unstable isotopes. The reason why we still find uranium in nature is the fact that the main isotope U238 (99.27%) decays very slowly (half-life of 4.468*10^9 years), whereas U235 (0.72%), which is used in atomic reactors or nuclear bombs decays about 10 times faster.
This brings me to the second part of your question. As with uranium, most elements are a mixture of different isotopes, and because isotopes differ in the number of neutrons they also differ in the atomic mass. Therefore the atomic mass of an element in the periodic system always represents the mean atomic mass of the isotope mixture. In the case of chlorine, it is a mixture of 75.77% Cl35 and 24.23% Cl37, which both are stable isotopes of chlorine. If you calculate the mean atomic mass including the percentage of both isotopes, you will get the final atomic mass of 35.45 u.
hope its help