no more information is given 21 Question (Practice) See page 205 Igniting gunpow

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21 Question (Practice) See page 205 Igniting gunpowder produces nitrogen and carbon dioxide gas that propels a bullet by the reaction 2KNO,(s)--S(s) + 3C(s)- K,S(s) +N,(g) + 3CO2 (g) 3rd attempt Part 1 See Periodic Table Q See Hint If 3.45 g of KNO3 reacts with sufficient sulfur(S8) and carbon (C), how much P-Vwork will the gases do against an external pressure of 1.00 atm given the densities of nitrogen and carbon dioxide are 1.165 g/L and 1.830 g/L, respectively, at 20°C? kJ Part 2 See Hint If the reaction produces 74.5 kJ of heat, what is Efor the system? kj

Explanation / Answer

Part 1

Molecular weight of KNO3 = 101 g/mol, amount taken = 3.45 g. Hence no.of mole of KNO3 = (3.45/101) mol = 0.034 mol

Now in comparison to KNO3 , no. of moles of N2 = (0.034/2)=0.017 mol and no. of moles of CO2 = (0.017*3) = 0.051 mol respectively.

Temperature (T) = 200C = (273+20)K = 293 K

Workdone by N2 = P dV = dN*RT = 0.017*8.314*293 = 41.41 J

Workdone by CO2 = P dV = dN*RT = 0.051*8.314*293 = 124.24 J

Hence total work done = (41.41+124.24)J = 165.65 J = 0.166 kJ

Part 2

dE = dQ + dW = (74.5 - 0.166)kJ (negative sign is given when the work is done by the system)

= 74.33 kJ

The end

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