A chemistry graduate student is given 500. mL of a 1.60 M hydrocyanic acid (HCN) solution. Hydrocyanic acid is a weak acid with K_a = 4.9 times 10^-10. What mass of KCN should the student dissolve in the HCN solution to turn it into a buffer with pH = 9.16? You may assume that the volume of the solution doesn't change when the KCN is dissolved in it. Be sure your answer has a unit symbol, and round to 2 significant digits.

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water pollution kills aquatic life. aquatic life includes algae and other plant life that use photosynthesis. photosynthesis takes   c02 out of the air.  

c02is a greenhouse gas.

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