What is the rate constant of a first-order reaction that takes 490 secondsseconds for the reactant concentration to drop to half of its initial value

Using a value of ksp = 1.8 x 10-2 for the reaction pbcl2 pb+2(aq) + 2cl -(aq). if the value of ksp was determined to be only 1.2 x 10-2: too much solid has dissolved. additional precipitate is forming. the solution is unsaturated. the ions are now combining to reduce their concentrations.

At 300 mm hg, a gas has a volume of 380 l, what is the volume at standard pressure

How do you know when a chemical reaction has occurred