If a mixture of gases has a total pressure of 257 mmHg, and is contains 87 mmHg of N2, and 46 mmHg of O2, what is the pressure of the third gas, Ar in mmHg?
(Answer with the three significant figures, but do not include units.)

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