열용량과 비열. 중화열

열용량과 비열. 중화열

 

 

A quantity of 200 mL of 0.862 M HCl is mixed with 200 mL of 0.431 M Ba(OH)2 in a constant pressure calorimeter of negligible heat capacity. The initial temperature of the HCl and Ba(OH)2 solution is the same at 20.48 ℃. For the process H+(aq) + OH-(aq) → H2O(l) the heat of neutralization is –56.2 kJ/mol.

What is the final temperature of the mixed solution?

Assume the density of the solution is the same as that of water (1.00 g/mL), and the specific heat of the solution is the same as that for pure water (4.184 J/g•℃).

 

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0.862 mol/L × 0.200 L

= 0.1724 mol HCl = 0.1724 mol H+

 

0.431 mol/L × 0.200 L

= 0.0862 mol Ba(OH)2 = 0.1724 mol OH-

Ba(OH)2(aq) → Ba2+(aq) + 2OH-(aq)

 

H+(aq) + OH-(aq) → H2O(l)

H+ : OH : H2O = 1 : 1 : 1 이므로,

생성된 H2O의 몰수 = 0.1724 mol H2O

 

중화열 = (-56.2 kJ/mol) × 0.1724 mol

= -9.689 kJ = -9689 J

 

q = C m Δt

Δt = q / C m

= 9689 J / [(4.184 J/g•℃)(400 g)]

= 5.79 ℃

 

final temperature = 20.48 + 5.79 = 26.27

 

답: 26.27 ℃