Boiling water weighing 200 g was poured into a porcelain cup weighing 100 g at a temperature of 20 C.

Boiling water weighing 200 g was poured into a porcelain cup weighing 100 g at a temperature of 20 C. The temperature of the cup with water turned out to be 90 C. Determine the specific heat of porcelain. Disregard the heat loss of a cup of boiling water.

Given:
m1 (porcelain) = 100 g = 0.1 kg
m2 (water) = 200 g = 0.2 kg
t1 (f) = 20 C
t2 (f) = 90 С
t1 (c) = 100 С
t2 (c) = 90 С
s2 (c) = 4200 J / kg * C
Find c1 (f) =?
Decision:
Qf = Qw
c1m1 (t2f-t1f) = c2m2 (t1v-t2v)
From here
c1 = c2m2 (t1v-t2v) / m1 (t2ph-t1ph)
c1 = 4200 J / kg * C * 0.2 kg * (100-90 C) / 0.1 kg * (90-20 C) = 1200 J / kg * C
Answer: c1 = 1200 J / kg * C