<h3>
Answer:</h3>
250.756 moles He
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Explanation:</h3>
From the question we are given;
Volume, L = 685 L
Temperature, T = 621 K
Pressure, P = 189 × 10 kPa
We are required to calculate the number of moles of the gas,
Using the Ideal gas equation,
PV = nRT, where P is the pressure, V is the volume, T is the temperature, n is the number of moles, and R is the ideal gas constant.
We can replace the known variables and constant in the equation to get the unknown variable, n.
Using ideal gas constant as 8.3145 L.kPa/K/mol
n = 250.756 moles
The moles of helium contained in the sphere is 250.756 moles
It will take 1.11 min to heat the sample to its melting point.
Melting point = - 20°C
Boiling point = 85°C
∆H of fusion = 180 J/g
∆H of vap = 500 J/g
C(solid) = 1.0 J/g °C
C(liquid) = 2.5 J/g °C
C(gas) = 0.5 J/g °C
Mass of sample = 25 g
Initial temperature = - 40°C
Final temperature = 100°C
Rate of heating = 450 J/min
Specific heat capacity formula:- q = m ×C×∆T
Here, q = heat energy
m = mass
C = specific heat
∆T = temperature change
Melting point = - 20°C
C(solid) = 1.0 J/g °C
∆T = final temperature - initial temperature = -20 - (-40) = 20
Put these value in Specific heat capacity formula
q = m ×C×∆T
q = 25×1.0×20
=500J
The Rate of heating = 450 J/min
i.e. 450J = 1min
so, 500J = 1.11min
1.11 minutes does it take to heat the sample to its melting point.
The specific heat capacity is defined as the amount of heat absorbed in line with unit mass of the material whilst its temperature increases 1 °C.
Learn more about specific heat capacity here:- brainly.com/question/26866234
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