They need more oxygen to function, so gas exchange needs to increase
The free fall of the phone is an uniformly accelerated motion toward the ground, with constant acceleration equal to

So, assuming the downward direction as positive direction of the motion, since the phone starts from rest the distance covered by the phone after a time t is given by

And if we substitute t=2.7 s, we find the distance covered:
Answer:
The balanced equation is 3NaBr+1H3PO4 ----> 1Na3PO4 + 3HBr
This is a double replacement because you are switching both the Na and the Hydrogen.
Explanation: