1.An ideal gas is at 30 C. The gas is cooled, reducing the thermal energy by 25%

Question

1.An ideal gas is at 30 C. The gas is cooled, reducing the thermal energy by 25%. What is the new temperature in C?

2. The lowest pressure ever obtained in a laboratory setting is 4.0×1011 Pa. At this pressure, how many molecules of air would there be in a 40 C experimental chamber with a volume of 0.090 m3 ?

3. A diver named Jacques observes a bubble of air rising from the bottom of a lake (where the absolute pressure is 3.50 atm) to the surface (where the pressure is 1.00 atm). The temperature at the bottom is 4.00 C, and the temperature at the surface is 23.0 C. part A. What is the ratio of the volume of the bubble as it reaches the surface (Vs) to its volume at the bottom (Vb)?

Explanation / Answer

1.Answer:

you have to use Kelvin or absolute degrees when making these calculations; this is because zero on the centigrade scale does not represent the lowest possible temperature

so lowering the temp by 25% will lower the thermal energy by 25 percent,

but here we have to realize the starting temp is 303K, and we will reduce the temp to 75% of 303K =

227.25 K = - 45.750C

2.Answer:

n=(PV)/(RT) where R is related to the Boltzmann constant, k,

by R = k*N, where k = 1.3806 x 10-23 J K^-1
=(4.0*10^-11 Pa * 0.90 m^3) / (1.3806 * 10^-23 J*K^-1 * 313 K)
=8.33 * 10^9

3.Answer:

pv=nrt
(pv)/t =nr

nr is constant

(3.5 Vb)/(4+273) = Vs/(23+273)

Vs/Vb = 1036/277

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