Step 1 :Given: m_substance = 170 g, T_initial_substance = 120 °C, m_water = 200 g, T_initial_water = 10 °C, T_final_mixture = 12.6 °C, c_water = 4.18 J/g°C
Step 2 :Using the formula q_substance = q_water, we have: 170 * c_substance * (12.6 - 120) = 200 * 4.18 * (12.6 - 10)
Step 3 :Solving for c_substance, we get: c_substance = \(\frac{200 * 4.18 * (12.6 - 10)}{170 * (12.6 - 120)}\)
Step 4 :Calculating the value, we get: c_substance = -0.119 J/g°C
Step 5 :\(\boxed{-0.119}\) J/g°C is not physically meaningful. There might be an error in the given data or the problem statement.