4) A 4.00 L balloon is filled with 0.297 moles of helium gas with a pressure of 0.910 atm. Calculate the temperature, in Kelvin, of the gas. (KEEP 3 SIG

FIGS; DO NOT TYPE ANY UNITS)*

149

Explanation:

Using the ideal gas equation; PV = nRT

P= Pressure = 0.910 atm,     T= Temperature = ?

V= Volume = 4.0L                  R = Gas constant = 0.08206 L.atm/mol/K

n = number of moles = 0.297

Making 'T' the subject of the formular, we have;

T = P V/ n R   =  0.910  x 4  /  0.297 x 0.08206

                       =  149

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

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