20g of NaOH was dissolved in 500cm ^3 of water , find the concentration of the solution

Name the element in group 17, period 2. (periodic table)

Mary is conducting an experiment on how pollution affects plant growth. how can she ensure that her data are reliable?

Which statement is true about a catalyst? a: a catalyst decreases the rate of the reaction. b. a catalyst is consumed during a chemical reaction. c. a catalyst lowers the activation energy of a reaction. d. a catalyst increases the reactant concentration during a reaction.