I really need help with these. Please explain.

|using the periodic tablewarm-upuse the periodic table in the tools bar to answer the following questions. what elemental classification does oxygen belongto? done

Chemistry worksheet - i am not sure what they are asking for exactly?

How does a catalyst increase the speed of a reaction? a. the catalyst eliminates the activated complex stage, allowing products to form immediately. b. the catalyst lowers the energy level of the reactants, making it easier for them to react. c. the catalyst makes it easier for the activated complex to form, lowering the activation energy. d. the catalyst raises the energy level of the products, making the reaction finish sooner. reset next