How much work is done on (or by) the gases in each of the following at 298 K and

Question

How much work is done on (or by) the gases in each of the following at 298 K and 1 atm? Indicate whether the work is done on or by the gas.

(a) condensation of 17.3 g of water WebAssign will check your answer for the correct number of significant figures. kJ work done on the gas work done by the gas no work done

(b) reaction of 4.5 g Na(s) and 12.0 g Cl2(g) to produce NaCl(s) WebAssign will check your answer for the correct number of significant figures. kJ work done on the gas work done by the gas no work done

(c) decomposition of 10.0 g KClO3 into KCl(s) and O2(g) WebAssign will check your answer for the correct number of significant figures. kJ work done on the gas work done by the gas no work done

(d) reaction of 7.8 g of H2(g) with 4.0 g of CO2(g) to produce H2O(g) and CO(g) WebAssign will check your answer for the correct number of significant figures. kJ work done on the gas work done by the gas no work done

Explanation / Answer

(a)

in condensation work done on the system .

moles of water = 17.3 / 18 = 0.96

work = n R T = 0.96 x 8.314 x 10^-3 x 298

       = 2.38 kJ

(b) reaction of 4.5 g Na(s) and 12.0 g Cl2(g) to produce NaCl(s) WebAssign will check your answer for the correct number of significant figures. kJ work done on the gas work done by the gas no work done

2Na + Cl2 --------------------> 2 NaCl

46g      71g                              2 x 58.5g

4.5g     12.0g                             ?

for 4.5 g Na ---------------> 4.5 x 71 / 46 = 6.94 g Cl2 needed

so moles of Cl2 for this consumption= 6.94 / 71 = 0.098

work = 0.098 x 8.314 x 10^-3 x 298

        = 0.24 kJ

here work done by the gas

(c) work done by the gas

(d) work done by the gas

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