When an oxygen atom forms an ion, it gains two electrons. what is the electrical charge of the oxygen ion?

a.
+1

b.
-1

c.
-2

d.
+2

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

Energy flows from the producer level to the level. is called

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.