Chemistry Homework week 5-6

# Chemistry Homework week 5-6 -...

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5.29: A sample of nitrogen gas kept in a container of volume 2.3 L and at a temperature of 32<sup>o</sup>C exerts a presure of 4.7 atm. Calculate the number of moles of gas present. Answer: moles of nitrogen gas(n) = [4.7atm x (2.3L/K(mol))] / [(.0821L(atm)/K(mol)) x (273+32K)] moles of nitrogen gas = 0.43moles 5.31 What volume will 5.6 moles of sulfur hexafluoride (SF<sub>6</sub>) gas occupy if the temperature and pressure of the gas are 128<sup>o</sup>C and 9.4 atm? Answer: V=[5.6moles x (.0821L(atm)/K(mol)) x (273+128)K]/ 9.4 atm V= 20 L 6.35 Calculate the heat of decomposition for this process at constant pressure and 25<sup>o</sup>C: CaCo<sub>3</sub>(<i>s</i>) ---> CaO(<i>s</i>) + CO<sub>2</sub>(<i>g</i>) Answer: &Delta;H<sup>o</sup><sub>Rxn</sub>=[1mol(-635.6kJ/mol) + 1mol(-393.5kJ/mol)] -
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Unformatted text preview: [1mol(-1206.9kJ/mol)] &Delta;H<sup>o</sup><sub>Rxn</sub>= 177.8kJ 6.73 Methanol (CH<sub>3</sub>OH) is an organic solvent and is also used as fuel in some automobile engines. From the following data, calculate the standard enthalpy of formation of methanol: 2CH<sub>3</sub>OH(<i>l</i>) + 3O<sub>2</sub>(<i>g</i>) - 2CO<sub>2</sub>(<i>g</i>) + 4H<sub>2</sub>O(<i>l</i>) &Delta;H<sup>o</sup><sub>Rxn</sub>= -1452.8kJ Answer: &Delta;H<sup>o</sup><sub>f</sub>(CH<sub>3</sub>OH, <i>l</i>) = {[2mol(-393.5kJ/mol) + 4mol(-187.6kJ/mol)] – (-1452.8kJ)} / 2mol &Delta;H<sup>o</sup><sub>f</sub>(CH<sub>3</sub>OH, <i>l</i>) = -42.3 kJ/mol...
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