1. directions: select each correct answer.

biotic factors of an ecosystem could include which of the following?

a. all types of plants
b. the quantity of water available
c. the temperature range
d. all animal populations

Which of the following is always a reactant in a combustion reaction? oxygen nitrogen hydrogen carbon

13. a covalent bond between two atoms is likely to be polar if: a. one of the atoms is much more electronegative than the other. b. the two atoms are equally electronegative. c. the two atoms are of the same element. d. the bond is part of a tetrahedrally shaped molecule. e. one atom is an anion.

To calculate percent by mass, use the equation below: calculate the percent by mass of each element. %n = % %h = % %o = %