Question

The standard molar entropy of NHz is 192.45 JK+mol-1 at 298K, and its heat capacity is given by the equation Com= a +bT +c/T2 with the coefficients given in the table below. Calculate the standard molar entropy of NH3 at 100 °C. Please explain as much as possible. Why did you use the equation? Or what conditions did you see from the question? etc. Table 1: Temperature variation of molar heat capacities, Cp /K-mol-?) = a +bT + c/T2 b/(10-3K-1) 25.1 c/(105 K) -155 NH3 29.751 T

Answer 1

briven data Scwg) = 192.45 TK molt standard molar entropy (sm) (p, m = (a + b + c) J K molt Ta bt(183ke) / (10542) NH3 29-75251 - 155 Som ) = ? We know that entropy variation with temperature is given by below formula son tf = Sam TP + Gram Tf where in a standard molar heal capacities so According to the given condition S (3434) = Sud (2986) 4.3"(a+b7+9) d> J* *my 2 Sm 373 88k) +31 (a+b +c) dt 2 I t t molt T2 → Smk373) = 50 5.372 (250mm 29Y So gange = singa [unt 7.3+ b[733+ e Fitnes} skambie 2) Smeg 18= 19245J**+29.75 [ In 1873-298)]+ b[373-293K - T i ga Cutting b, a &c value from given data table also = 192.45JK+89.75 in 75 k.+ 251x10*x15- 155x18 2 TSx2 m. 3135 - 13 3}Jktmold

Som15** *5 4,373** 193.45 3K Mar 29.75 An (46) +95-1.6 16x16 - 255x16 Note Constant value of c in your datatable at 155 bed in atkin physical chemashy Fuso once reckon 1.55 But I am following your dała table, doing calodahon Sm 3+3* = 19245 + 128.41 +1-8825 - 1377.78} TK mel? $,323 = - 1054.98 JK 'me! Hence mentropy of ammonia at 100°C temperature decrease due to negative sign come. Hence it is not correct, due to your data value of constant c is wrong Now putting correct value C = 155x10K2 Sm., 3731 = 192.45 +$24.75 in 75+ 2.5.1.x10²x15 - 1.55110) JK Tart Sm2736 = (192.45 +128.47+ 1.9925 - 13.78)Jkmere 2x 18°,273 = 309.03 Jkmal2| Standard molar entropy of NHz ał 100*687 373 k

The equation C_p,m = a + bT + c/T²

This equation is use because heat capacity is varies with change in temperature is large amount, Normally we neglect heat capacities changes with small variation in temperature. This equation is use where your compound is more effective or responsive with temperature.