Which statement best describes the use of a catalyst in a fuel cell? it reduces waste. it lowers energy requirements. it reduces toxic exhaust. it increases reaction rates.

Option (d) is the correct answer.

Explanation:

A catalyst is a substance that helps in increasing the rate of a chemical reaction without itself getting consumed in the reaction.

Basically, a catalyst decreases the activation energy gap so that molecules with less energy can also participate in the reaction. Hence, rate of reaction increases due to which products are obtained quickly.

Thus, we can conclude that the statement, it increases reaction rates increases reaction rates.

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j