Why are atmospheric co2 concentrations low in the northern hemisphere in summer and high in the winter? see section 53.3 (page 1130) ?

Which statement is best described as a atom

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.

The diagin dilutepage 6 of 12a6a5(a)fluorine, chlorine, bromine and iodine are placed in the same group of theperiodic table.state the common name used to describe elements in this group.(i)state the group in which the elements are placed and explain whythey are placed in that group.(ii)which of the above named elements is a solid at roomtemperature and pressure?