CHEM 1A03 Chapter Notes - Chapter Unit 8 Module 2: Heat Capacity, Intermolecular Force, Hydrogen Bond

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CHEM 1A03 Full Course Notes

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We can think of heat capacity of a system as its ability to resist temperature change when energy is added to, or removed from, the system. Temperature change comes from the translation of molecules when energy is added it is a measure of kinetic energy. Water can resist translation because of the strong intermolecular forces hydrogen bonding: this is why water has such a strong heat capacity. The more complex a molecule is, the more internal degrees of freedom it has, and generally, the higher its specific heat capacity. Molar heat capacity is similar to specific heat (cid:272)apa(cid:272)it(cid:455), (cid:271)ut defi(cid:374)es the (cid:862)s(cid:455)ste(cid:373)(cid:863) as 1 (cid:373)ol of (cid:373)ate(cid:396)ial. Qrxn the quantity of heat exchanged between a system and its surroundings when a chemical reaction occurs within the system at constant temperature. When a reaction is carried out at constant temperature: If qrxn is negative reaction releases heat = exothermic. If qrxn is positive the reaction absorbs heat = endothermic.

Related Questions

1. The amount of energy released by burning a fuel source, measured in energy per mass, is called the fuel value. If all the energy obtained from burning 1.23 pounds of ethane (fuel value is 11.36 kcal/g) is used to heat 121.0 kg of water at an initial temperature of 20.6C, what is the final temperature?

2. A 1445 kg car is traveling down the road at 93.0 km/h. while traveling at this rate of speed, what is the kinetic energy of this vehicle in kilojoules?

3. when 1576 j of heat energy is added to 38.7 g of hexane, C6H14, the temperature increases by 18.0 C . calculate the molar heat capacity of C6H14.

4. If a system has 2.50 x 10^2 kcal of work done to it, and releases 5.00 x 10^2 kj of heat into its surroundings, what is the change in internal energy of the system?

5. when a 3.00 -g sample of RbBr is dissolved in water in a calorimeter that has a total heat capacity of 0.9690 kj .K^-1, the temperature decreases by 0.410 K, calculate the molar heat of solution of RbBr

When 0.595 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 25.4 âC to 29.9 âC.

Part A

Find ÎErxn for the combustion of biphenyl in kJ/mol biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/âC.

Part B

Learning Goal: To understand the concepts of heat capacity, specific heat, and molar heat capacity. Heat capacity, C, is the amount of energy required to raise the temperature of a substance by exactly 1 degree Celsius. The energy needed to warm an object increases as the mass of that object increases. We see this in our everyday life. For example, we know that it takes much more energy to heat a large tank of water than a small cup. Because of this dependence on mass, experimentally determined heat capacities are always reported in terms of the amount of the substance that is heated. One method is to report how much energy it takes to raise the temperature of one mole of a substance by exactly 1 degree Celsius. This value is the molar heat capacity, which has the symbol Cp.The molar heat capacity is given in the units J/(molâ âC). A second method is to report how much energy it takes to raise the temperature of one gram of a substance by exactly 1 degree Celsius. This value is the specific heat, which has been given the symbol Cs. The units for specific heat are J/(gâ âC). The heat capacity of a substance is therefore related to the energy q needed to raise its temperature by an amount ÎT. That is, q=nCpÎT, where n denotes the number of moles of the substance, or q=mCsÎT, where m denotes the number of grams of the substance.

Part 1

It takes 55.0 J to raise the temperature of an 9.90 g piece of unknown metal from 13.0âC to 24.8 âC. What is the specific heat for the metal?

Express your answer with the appropriate units.

Part 2

The molar heat capacity of silver is 25.35 J/molâ âC. How much energy would it take to raise the temperature of 9.90 g of silver by 16.0 âC?

Express your answer with the appropriate units.

Part 3

What is the specific heat of silver? Express your answer with the appropriate units.

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CHEM 1A03 Chapter Notes - Chapter Unit 8 Module 2: Heat Capacity, Intermolecular Force, Hydrogen Bond

CHEM 1A03 Full Course Notes

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