The steel bar was immersed in a vessel containing 20 kg of water at a temperature of 90 ° C.

The steel bar was immersed in a vessel containing 20 kg of water at a temperature of 90 ° C. What temperature will be established in the vessel if the water gives off 840 kJ of heat during cooling?

Problem data: m (mass of water in the vessel) = 20 kg; t0 (temperature in the vessel before immersion of the steel bar) = 90 ºС; Q (amount of heat delivered) = 840 kJ (840 * 103 J).

Reference values: Cw (specific heat of water) = 4200 J / (kg * K).

The temperature established in the vessel can be expressed from the formula: Q = Cw * m * (t0 – t), whence t = t0 – Q / (Cw * m).

Calculation: t = 90 – 840 * 103 / (4200 * 20) = 80 ºС.

Answer: After the immersion of the steel bar, the temperature in the vessel will be set to 80 ºС.