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Model Paper 7 — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryModel Paper 73 Marks
Question
1. The fact that the enthalpy is a state function forms the basis of a very useful law. Name the law.
2. Two liters of an ideal gas at a pressure of 10 atm expands isothermally at $25^{\circ} C$ into a vacuum until its total volume is 10 liters. How much heat is absorbed and how much work is done in the expansion?
3. A sample of 1.0 mole of a monoatomic ideal gas is taken through a cyclic process of expansion and compression as shown in the figure. What will be the value of $\Delta H$ for the cycle as a whole?
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Answer

1. The name of the law is Hess's law of heat summation.
2. We have $q =- w = p _{ ex }(10-2)=0(8)=0$ No work is done; no heat is absorbed.
3. According to the question, 1 mole of a mono atomic ideal gas is taken through a cyclic process of expansion and compression.
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$\Delta H$ for a cyclic process is zero because enthalpy change is a state function.

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