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Heat Loss and Specific Heat

a) A student wishes to determine the specific heat of a metal using a coffee cup calorimeter (calorimeter constant 50.35 cal/degrees Celsius). The student heats 130.56 grams of unknown metal from 25.0 degrees Celsius to 100.4 degrees Celsius. The initial temperature of the calorimeter (coffee cup plus 30 mL water) was 23.5 degrees Celsius. The student then adds the hot metal to the coffee cup and temperature changes until equilibrium occurs. The equilibrium temperature is 30.5 degrees Celsius. Answer the following two questions:

1. How much heat is lost by the metal and what is it gained by?
2. What is the secific heat of the unknown metal?

b) A compound containg only carbon and hydrogen is 7.74% H by mass and has a molar mass of 78.1 g/mol. Determine the empirical and molecular formulae of the compound.

c) An isotope of a neutral atom has 19 electrons and 22 neutrons? Give the atomic symbol of the element.

Solution Preview

1. The heat lost by the metal is gained by the water and the calorimeter.

(50.53 cal/deg C)(30.5 deg C - 23.5 deg C)
+ (30 g)(1.00 cal/g*deg C)(30.5 deg C - 23.5 deg C)
= 564 cal

2. Specific heat is how much heat something absorbs per degree Celsius per gram. In other words, J/(g*degC). Heat capacity is ...

Solution Summary

The solution can be found by solving for the heat lost by the metal equal to the heat that the calorimeter and water absorb. In other words (deltaH of calorimeter and water) = - (deltaH of metal).