I need help in 5 and 6

Consider the four elements above. which one of these elements will combine with oxygen in a 1: 1 ratio?

650.j is the same amount of energy as? 2720cal1550cal650.cal2.72cal

The solid xy decomposes into gaseous x and y: xy(s) m x(g) + y(g) kp = 4.1 (at 0 °c) if the reaction is carried out in a 22.4 l container, which initial amounts of x and y will result in the formation of solid xy?