Question

A 215-g sample of a substance is heated to 350 ∘C and then plunged into a 105-g aluminum calorimeter cup containing 185 g of water and a 17-g glass thermometer at 12.5 ∘C. The final temperature is 35.0∘C. The value of specific heat for aluminium is 900 J/kg⋅C∘ , for glass is 840 J/kg⋅C∘ , and for water is 4186 J/kg⋅C∘

What is the specific heat of the substance? (Assume no water boils away.)

Express your answer using three significant figures.

Answer 1

heat rejected by the substance will be absorbed by aluminium calorimeter , water and glass thermometer.

dQ = mc dT

where m is mass

c is the specific heat

and dT is change in temperature.

m_sub c_sub (T_{i sub} - T_final ) = m_Al c_Al (T_final - T_{i Al} ) + m_w c_w (T_final - T_{i w} ) + m_g c_g (T_final - T_{i g})

m_sub c_sub (T_{i sub} - T_final ) = 0.105 kg x 900 J/kg C⁰ ( 35 - 12.5 ) + 0.185 kg x 4186 J/kg C⁰ ( 35 - 12.5 ) +0.017 kg x 840J/kg C⁰ (35 - 12.5)

m_sub c_sub (T_{i sub} - T_final ) = 883. 19 x 22.5

0.215 kg x c_sub (350 - 35) = 883. 19 x 22.5

c _sub = (883. 19 x 22.5) / ( 0.215 x 315 )

c_sub = 293.4186 J/kgC⁰