Describe in your own words, in terms of particle movement and energy, what occurs when a liquid is heated to its boiling point.
1 answer:
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Answer:
(a) 45.17×10^-14 kg/s
(b) since the amount of helium escaped due to diffusion is insignificant, the final pressure drop in the tank remains the same as the initial pressure 500kPa.
Explanation:
Helium gas at temperature T=293k
Helium gas at pressure P= 500kPa
The inner diameter of spherical tank is
The inner radius of spherical tank is :
=
=1m
Thickness of the container r = 1cm =0.01m
Outer radius of the spherical tank is ;
t =
multiplying through with (-) we have ;
From table of binary diffusion coefficients of solids, the diffusion coefficients of helium in silica is noted as
From table molar mass and gas constant, the molecular weight of helium is:
M = 4.003kg/kmol
The solubility of helium in fused silica is determined from Table of Solubility of selected gases and soilids.
= 0.00045 kmol/m³. bar
Considering total molar concentration as constant, the molar concentration of helium inside the container is determined as
= 0.00045kmol/m³. bar × (5)
From one dimensional mass transfer through spherical layers is expressed as:
substituting all the values in the above relation, we have;
(a) The mass flow rate is expressed as
(b) The pressure drop in the tank after a week;
For one week the mass flow rate of helium is
The volume of the spherical tank is
V = 4.189m³
The initial mass of helium in the sphere is determined from the ideal gas equation:
PV=NRT
where R is the universal gas constant and its value is R = 8.314 KJ/Kmol.k
N= PV/RT
N= 500 × 4.189/ 8.314 × 293
N= 0.86kmol
The number of moles of helium gas remaining in the tank after one week is:
therefore, since the amount of helium escaped due to diffusion is insignificant, the final pressure drop in the tank remains the same as the initial pressure 500kPa.
Answer:
Highest speed: He
Lowest speed: CO2
Explanation:
The rms speed (average speed) of the molecules/atoms in an ideal gas is given by:
where
R is the gas constant
T is the absolute temperature of the gas
M is the molar mass of the gas, which is the mass of the gas per unit mole
From the equation, we see that at equal temperatures, the speed of the molecules in the gas is inversely proportional to the molar mass: the higher the molar mass, the lower the speed, and vice-versa.
In this problem, we have 5 gases:
(CO2) (O2) (He) (N2) (CH4)
Their molar mass is:
CO2: 44 g/mol
O2: 16 g/mol
He: 4 g/mol
N2: 14 g/mol
CH4: 16 g/mol
The gas with lowest molar mass is Helium (He): therefore, this is the gas with greatest average speed.
The gas with highest molar mass is CO2: therefore, this is the gas with lowest average speed.