The Decomposition of Phosphine,PH₃,follows First-Order Kinetics

Multiple Choice

The decomposition of phosphine,PH₃,follows first-order kinetics. 4 PH₃(g) → P₄(g) + 6 H₂(g)
The half-life for the reaction at 550 °C is 81.3 seconds.What percentage of phosphine remains after 195 seconds?

A) 2.2%
B) 9.8%
C) 19%
D) 42%
E) 58%