For a concentration cell, the standard cell potential is always:. a. positive
b. negative
c. zero
d. need more information

C. Zero

Explanation:

A concentration cell is defined as a type of galvanic cell which has two equivalent half-cells of the same constituent in the electrodes but different concentration in the electrolytes.

For a concentration cell, the standard cell potential is always Zero and the cell potential is usually measured with the use of the Nernst equation.

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.