1. Assume the dimensions of this classroom are 15m x 15 m x 4 m. Using the Ideal
ID: 1972251 • Letter: 1
Question
1. Assume the dimensions of this classroom are 15m x 15 m x 4 m.Using the Ideal Gas Law, estimate the number of moles of air present in the
classroom. How many air molecules is this?
(Do not use the density of air in this step. Density will be determined in step 2.)
2. Use your answer to question 1 to estimate the total mass of the air in the lab in kg.
What is the density of the air in the lab in kg/m^3.
(The mass of one mole of air is 0.21 x 32 gram + 0.79 x 28 gram)
3. The specific heat of air is 22 J/(mole.C).
How much energy would be required to increase the air temperature in the lab by
3C?
Explanation / Answer
PV = nRT
n = PV/RT
= (1 atm) (15*15*4*100 Litres)/(0.082057 * 298) ( taking atmospheric pressure 1 atm and atmospheric temperaure 298 K)
= 36805.32
2.
mass of one mole of air = .21*32 + .79*28 = 28.84 gram (given)
mass of 36805.32 moles = 28.84 * 36805.32 /1000 kg = 1061.465 kg
density = m/v = 1061.465 kg /(15*15*4 m3) = 1.1794 kg/m3
3.
energy required = specific heat * no. of moles * required increase in temp
= 22 * 36805.32 * 3 = 2.43 mega joules
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