Energy Changes lll Cliti Review Questions 6.7 Define these terms: thermochemistr
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Question
Energy Changes lll Cliti Review Questions 6.7 Define these terms: thermochemistry, exothermic 6.8 6.9 Describe two exothermic processes and 6.10 Decomposition reactions are usually endothermic, process, endothermic process. Stoichiometry is based on the law of conservation of mass. On what law is thermochemistry based? two endo- thermic processes. whereas combination reactions are usually exother- mic. Give a qualitative explanation for these trends. First Law of Thermodynamics Review Questions 6.11 On what law is the first law of thermodynamics based? Explain the sign conventions in the equation 6.12 Explain what is meant by a state function. Give two R 6. two two that are not. 6.13 The internal energy of an ideal gas depends only on its temperature. Do a first-law analysis of this cess. A sample of an ideal at constant temperatur pro- gas is allowed to expand e against atmospheric pressure 6.Explanation / Answer
11.
The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.
U = q + w
In this case, w is defined as the work done *on* the system *by* the surroundings. Now positive work increases the internal energy of the system, and negative work decreases it. This convention is a little more consistent, in that positive signs for q and w are both associated with quantities going *into* the system (q is the heat added *to* the system, and w is work done *on* the system).
19.
Sn(s) + 2H+(aq) ==> Sn(2+)(aq) +H2(g)
The work is done by releasing H2 gas.
The molar mass of Sn: 118.71 g/mol.
50.0g Sn <=> 0.421 mol Sn ==> reacted to get 0.421 mol H2
==> W = nRT = 0.421*8.314*298 = 1.04 kJ
33. q =C(T)
q =(0.385 J/g.oC)(303.8 oC)
q =116.96 J/g x 6220 g
q =727.51 kJ
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