A5.0-gram sample of fe(s) is to be placed in 100. milliliters of hcl(aq). which changes will result in the fastest rate of reaction?

Raising the temperature of the reactants increases the reaction between the reactants. The kinetic energy of the molecules of the reactants collides more frequently with ach other thereby increasing its reaction. Increasing the concentration of the reactants increases the reaction rate. Adding a catalyst to the reaction increases the rate of reaction of a substance. The catalyst hastens the chemical reaction. 

Cr(oh)3 -> cr(3+) + 3oh-