Question

1. A hot lump of 46.2 g of iron at an initial temperature of 77.9 °C is placed in 50.0 mL of H2O initially at 25.0 °C and allowed to reach thermal equilibrium. What is the final temperature of the iron and water given that the specific heat of iron is 0.449 J/(g·°C)? Assume no heat is lost to surroundings. 2.When 1422 J of heat energy is added to 40.8 g of hexane, C6H14, the temperature increases by 15.4 °C. Calculate the molar heat capacity of C6H14. 3.A 39.88 g sample of a substance is initially at 22.7 °C. After absorbing 1159 J of heat, the temperature of the substance is 135.2 °C. What is the specific heat (c) of the substance? 4.If the heat of combustion for a specific compound is -1030.0 kJ/mol and its molar mass is 75.87 g/mol, how many grams of this compound must you burn to release 324.00 kJ of heat?

Answer 1

Q1. A hot lump of 46.2 g of iron at an initial temperature of 77.9 °C is placed in 50.0 mL of H2O initially at 25.0 °C and allowed to reach thermal equilibrium.

What is the final temperature of the iron and water given that the specific heat of iron is 0.449 J/(g·°C)? Assume no heat is lost to surroundings.

Apply:

-Heat lost = Heat gained

-m1*C1*(Tf-T1) = m2*C1*(Tf - T2)

-46.2*0.449*(Tf-77.9) = 50*4.184(Tf-25)

-20.7438Tf + 77.9*20.7438 = 209.2Tf - 25*209.2

Tf(-209.2-20.7438) = -25*209.2 -  77.9*20.7438

Tf = (-6845.942)/(-209.2-20.7438)

Tf = 29.7722°C

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