Question

A piece of brass of mass 200 g and at 100°C, is placed in 400 g of turpentine oil, contained in a copper calorimeter of mass 50 g at 15°C. The final temperature recorded is 23°C. Find the sp. heat capacity of turpentine oil.

[S.H.C. for brass = 370 Jkg⁻¹K⁻¹; S.H.C. of copper = 390 Jkg⁻¹K⁻¹]

Answer 1

Using SI units:

brass mass m_b = 0.2 kg

turpentine mass m_t = 0.4 kg

calorimeter mass m_c = 0.05 kg

Initial temperatures:

brass 100°C

turpentine and calorimeter = 15°C

final temperature θ = 23°C

Fall in temperature of brass:

θ_F = 100 − 23 = 77°C

Rise in temperature of turpentine and calorimeter:

θ_R = 23 − 15 = 8°C

Heat lost by brass:

Q_b = m_bc_bθ_F

= 0.2 × 370 × 77

= 5698 J

Heat gained by calorimeter:

Q_c = m_cc_cθ_R

= 0.05 × 390 × 8

= 156 J

Heat gained by turpentine:

Q_t = m_tc_tθ_R

= 0.4 × c_t × 8

= 3.2c_t J

By the principle of calorimetry,

Q_b = Q_t + Qc

5698 = 3.2c_t + 156

3.2c_t = 5542

$$c_t=\frac{5542}{3.2}$$

= 1731.875

≈ 1731.9 J kg⁻¹ K⁻¹