Questions

The given sentence is in simple past. No improvement required.

To get the mass of a mole of NaCl, we need to add the molar atomic weights of the individual elements i.e, Na and Cl

Atomic weights of Na = 22.99 gm/mol  Cl = 35.45 gm/mol

Now, mass of a mole of NaCl = 22.99 + 35.45 = 58.44 gm/mol.

The process which involves absorption of heat is endothermic.

Here given all the options are involving in absorption of heat. Hence, all the above are endithermic.

the least populated state in India as per Census 2011 is Sikkim.

Article 370 of the Indian constitution used to give special provision to the region of Jammu and Kashmir. It allows the state to have its own constitution, a separate flag and independence over all matters except foreign affairs, defence and communications. It was adopted in 1947 by then Prime Minister Jawaharlal Nehru.

Lothal

Cobalt therapy or cobalt-60 therapy is the medical use of gamma rays from the radioisotope cobalt-60 to treat conditions such as cancer.

Cobalt 60 is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors.