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mariahcrook7
03.01.2020 •
Physics
How much heat energy is required to convert 93.4 g of solid ethanol at − 114.5 ° c to gasesous ethanol at 149.8 ° c ? the molar heat of fusion of ethanol is 4.60 kj/mol , and its molar heat of vaporization is 38.56 kj/mol . ethanol has a normal melting point of − 114.5 ° c and a normal boiling point of 78.4 ° c . the specific heat capacity of liquid ethanol is 2.45 j / g ⋅ ° c , and that of gaseous ethanol is 1.43 j / g ⋅ ° c .
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Ответ:
Q' = 140.859 kJ
Explanation:
Given that, 93.4 g of solid ethanol at − 114.5 °C is converted to gasesous ethanol at 149.8 ° C.
The molar heat of fusion of ethanol is, ΔH(f) = 4.60 kJ/mol , and its molar heat of vaporization is ΔH(v) = 38.56 kJ/mol .
And also Ethanol has a normal melting point of − 114.5 ° C and a normal boiling point of 78.4 ° C .
The specific heat capacity of liquid ethanol is S(l) = 2.45 J / g ⋅°C , and that of gaseous ethanol is S(g) = 1.43 J / g ⋅°C .
Lets solve this step wise ;
Given 93.4 g of ethanol is taken, but 1 mole of ethanol consists of 46.06 g
⇒ moles of ethanol given =
= 2.02 moles
step 1: solid ethanol to liquid ethanol at melting point of − 114.5 ° C
⇒ 1 mole requires ΔH(f) = 4.60 kJ/mol of heat
⇒ heat required = 4.60 × 2.02 = 9.292 kJ.
step 2: liquid ethanol at -114 °C to liquid ethanol at 78.4 °C
Q = m×S×ΔT ; Q = heat required
m = mass of the substance
S = specific heat of the substance
ΔT = change in temperature
Here S = S(l);
⇒ Q = 93.4×2.45×(78.4-(-114.5))
= 44.141 kJ
step 3: liquid ethanol at 78.4°C to gaseous ethanol at 78.4°C
1 mol of liquid ethanol requires ΔH(v) = 38.56 kJ/mol of heat
⇒ required heat = 38.56×2.02 = 77.89 kJ
step 4: gaseous ethanol at 78.4 °C to gaseous ethanol at 149.8 °C
Q = m×S×ΔT
Here, S = S(g)
Q = 93.4×1.43×(149.8-78.4)
= 9.536 kJ
⇒ Total heat required = 9.292 + 44.141 + 77.89 + 9.536
= 140.859 kJ
⇒ Q' = 140.859 kJ
Ответ:
The heat loss per unit length is![\frac{Q}{L} = 2981 W/m](/tpl/images/0636/2517/b593a.png)
Explanation:
From the question we are told that
The outer diameter of the pipe is![d = 104mm = \frac{104}{1000} = 0.104 m](/tpl/images/0636/2517/38bc5.png)
The thickness is
The temperature of water is
The outside air temperature is![T_a = -10^oC = -10 +273 = 263K](/tpl/images/0636/2517/87bb9.png)
The water side heat transfer coefficient is![z_1 = 300 W/ m^2 \cdot K](/tpl/images/0636/2517/95237.png)
The heat transfer coefficient is![z_2 = 20 W/m^2 \cdot K](/tpl/images/0636/2517/6c8fe.png)
The heat lost per unit length is mathematically represented as
Substituting values