1a) 32.4 kg of liquid 1 comes in thermal contact with 74.4 kg of liquid 2. If li

Question

1a) 32.4 kg of liquid 1 comes in thermal contact with 74.4 kg of liquid 2. If liquid 1 has an initial temperature of 268 K, and a specific heat of 2.65 kJ/kg K, and liquid 2 has an initial temperature of 242 K, and a specific heat of 1.58 kJ/kg K, then what is the final temperature at thermal equilibrium? Assume the system is thermally isolated. 258 K

1b) The dissolution of barium hydroxide in water is an exothermic process. Which of the following statements is correct?

The enthalpy of solid barium hydroxide plus pure water is less than that of the solution, at the same temperature. The temperature of the solution is lower than of the barium hydroxide and water before mixing.

When barium hydroxide dissolves in water, the system does work on the surroundings.

The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution, at the same temperature. The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature.

Explanation / Answer

Q1 = M1*C1+(Tf-T1)

Q2 = M2*C2+(Tf-T2)

Q1 = -Q2

M1*C1(Tf-T1) = M2*C2+(Tf-T2)

32.4*2.65*(Tf-268) = -74.4*1.58*(Tf-242)

(32.4*2.65) / (-74.4*1.58) * (Tf-268) = (Tf-242)

-0.7304Tf - 268*-0.7304 = Tf - 242

Tf(-0.7304-1) = -242 +  268*-0.7304

Tf = -437.747 / (-0.7304-1) = 252.97 K

B)

Ba(OH)2 <-> Ba+2 + 2OH- + heat

The temperature of the solution is lower than of the barium hydroxide and water before mixing. --> TRUE

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