A 20-cm-diameter vertical cylinder is sealed at the top by a frictionless 23 kg piston. The piston is 86 cm above the bottom when the gas temperature is 307°C. The air above the piston is at 1.00 atm pressure.
A) What is the gas pressure inside the cylinder?
B) What will the height of the piston be if the temperature is lowered to 13°C?

Respuesta :

Answer:

108507.02596 Pa

42.42 cm

Explanation:

F = Force

m = Mass of piston = 23 kg

[tex]T_1[/tex] = Initial temperature = 307°C

[tex]T_2[/tex] = Final temperature = 13°C

[tex]P_o[/tex] = Outside pressure

[tex]P_i[/tex] = Pressure inside cylinder

A = Area of pistion

h = Height of piston

Change in pressure is given by

[tex]\Delta P=\frac{F}{A}\\\Rightarrow \Delta P=\frac{mg}{\pi r^2}\\\Rightarrow \Delta P=\frac{23\times 9.81}{\pi 0.1^2}\\\Rightarrow \Delta P=7182.02596\ Pa[/tex]

[tex]P_i-P_o=\Delta P\\\Rightarrow P_i=\Delta P+P_0\\\Rightarrow P_i=7182.02596+101325\\\Rightarrow P_i=108507.02596\ Pa[/tex]

Gas pressure inside the cylinder is 108507.02596 Pa

From ideal gas law we have the relation

[tex]\frac{V_1}{T_1}=\frac{V_2}{T_2}\\\Rightarrow \frac{Ah_1}{T_1}=\frac{Ah_2}{T_2}\\\Rightarrow \frac{h_1}{T_1}=\frac{h_2}{T_2}\\\Rightarrow h_2=\frac{h_1}{T_1}\times T_2\\\Rightarrow h_2=\frac{0.86}{307+273.15}\times (13+273.15)\\\Rightarrow h_2=0.42418\ m=42.42\ cm[/tex]

The height of the piston at 13°C will by 42.42 cm

(a) The gauge pressure inside the cylinder is 108,500 Pa.

(b) The height of the piston when the temperature is lowered to 13°C is 42.4 cm.

Change in gas pressure inside the cylinder

The change in the pressure of the gas inside the cylinder is calculated as follows;

ΔP = F/A

ΔP = mg/πr²

ΔP = (23 x 9.8)/(π x0.1²)

ΔP = 7,174.7 Pa

Gauge pressure inside the cylinder

The gauge pressure inside the cylinder is calculated as follows;

Pi = ΔP + Po

Pi = 7,174.7  +  101325

Pi = 108,500 Pa

Height of the piston

The height of the piston is calculated as follows;

[tex]\frac{V_1}{T_1} = \frac{V_2}{T_2} \\\\\frac{Ah_1}{T_1} = \frac{Ah_2}{T_2} \\\\h_2 = \frac{T_2h_1}{T_1} \\\\h_2 = \frac{(13 + 273) \times 0.86}{(307 + 273)} \\\\h_2 = 0.424 \ m[/tex]

h₂ = 42.4 cm

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