Question

Suppose that 145 g of ethanol at 20◦C is mixed

with 235 g of ethanol at 84 ◦C at constant

atmospheric pressure in a thermally insulated

vessel. What is the ∆Ssys for the process?

The specific heat capacity for ethanol is 2.42

J/g K.

Answer in units of J/K.

Answer 1

∆Ssys = 392.73-179.62 =213.11 J/K.

Step-by-step explanation:

m_1=145,T_1=20°C

and

m_2=235, T_2=84 °C

let, specific heat capacity be c(small)=2.42 J/g/K

let,

the constant temperature obtained after mixing is t

so heat absorbed(1st portion of ethanol),
`Q_1=m_1c(T-T_1)`

heat heat lost(2nd portion of ethanol), ,
`Q_2=m_2c(T_2-T)`

Now, heat lost= heat gained

,
`m_1c(T-T_1)`=
`m_2c(T_2-T)`

`145(T-20)`=
`235(84-T)`

T=61.25°C

`\Delta S_1= cm_1ln((T)/(T_1) )`

putting values we get

`\Delta S_1= 2.42*145ln((61.25)/(20) )`

ΔS_1= 392.73 J/ K.

and

`\Delta S_2= 2.42*235ln((61.25)/(84) )`

ΔS_2= -179.62557 J/K.

∆Ssys = 392.73-179.62 =213.11 J/K.