In a study of the gas phase decomposition of nitrogen

Question

In a study of the gas phase decomposition of nitrogen dioxide at 383 °C

NO₂(g)--->NO(g) + ½ O₂(g)

the concentration of NO₂ was followed as a function of time.

It was found that a graph of 1/[NO₂] versus time in seconds gave a straight line with a slope of 0.761 M^-1 s^-1 and a y-intercept of 2.55 M^-1. 

Based on this plot, the reaction is _______(zero/first/second) order in NO₂ and the rate constant for the reaction is _________M^-1 s^-1.

In a study of the gas phase decomposition of phosphine at 120 °C

PH₃(g)---->1/4 P₄(g) + 3/2 H₂(g) the concentration of PH₃ was followed as a function of time.

It was found that a graph of ln[PH₃] versus time in seconds gave a straight line with a slope of -2.86×10^-2 s^-1 and a y-intercept of -2.35. 

Based on this plot, the reaction is _______(zero/first/second) order in PH₃ and the rate constant for the reaction is ____________ s^-1.