Which of these describes an exothermic reaction?
a. energy is created in the reaction
b. energy is released by the reaction
c. energy is absorbed by the reaction
d. no energy is transferred by the reaction.

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

Given that 1 mi = 1760 yd, determine what conver- sion factor is appropriate to convert 1849 yd to miles; to convert 2.781 mi to yards.

The chemical equation below shows the reaction of sodium (na) and chlorine (cl) to form sodium chloride (nacl). 2na + cl2 → 2nacl in this equation, which of the following is a reactant? i. sodium ii. chlorine iii. sodium chloride