What mass of each gas is present in a 1.15 −l sample of this mixture at 25.0 ∘c?

total pressure = 666/760=0.876 atm

moles gas = 0.876 x 1.10 L / 0.08206 x 298 K=0.0394

moles N2 / 0.0394 = 330/ 666

moles N2 =0.0195

mass N2 = 0.0195 x 28.0134 g/mol= 0.546 g

moles O2 / 0.0394 = 126/666

moles O2 = 0.00745

mass O2 = 0.00745 x 32 g/mol=0.239 g

moles He/ 0.0394 = 210/ 666

moles He = 0.0124

mass He = 0.0124 x 4 g/mol=0.0497 g

pure substance: iron,copper

impure substance: water,charcoal

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