A certain reaction proceeds by first order kinetics. The half life of a reaction is 180s. What percent of the initial concentration remains after 900s?​

Bis the answerhope it !

Bthats what im doing to and i figured it out it is b

Hello thereone of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description? answer: atomic mass  was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.