Question

Name Answer all questions. I. Use the standard reaction enthalpies given below to determine ??.n for the following reaction Given: What is the enthalpy change (in kJ] of a chemical reaction that raises the temperature of 250.0 mL of solution having a density of 1.25 g/ml by 9.20°c? (The specific heat of the solution is 3.74 1/s C.)

Answer 1

Delta H_r times n^0 = ? for P_4(g) + 10 cl_2(g) rightarrow 4 Pcl_3(g) given Pcl_5(s) rightarrow Pcl_3(g) + cl_2(g) delta H^0_r times n = 157KJ rightarrow (1) P_4(g) + 6cl_2(g) rightarrow 4 Pcl_3(g) delta H^0_r times n = -1207 KJ rightarrow (2) therefore By multiplying equation (1) by 4 and reversing to it therefore 4 Pcl_3(g) + 4Cl_2 rightarrow 4Pcl_5(s).. delta H^0_r times n = 4 times 157 rightarrow (3) = 628 KJ P_4(g) + 6cl_2(g) rightarrow 4Pcl_3(g)... delta H^0_r times n = -1207 KJ rightarrow (4) therefore BY addition and conclusion of opposite terms P_4(g) + 10cl_2(g) rightarrow 4 Pcl_5(s) therefore delta H^0_r times n = 628 KJ + (- 12.7 KJ) = -579KJ therefore delta H^0_r times n, P_4(g) + 10cl_2(g) rightarrow 4Pcl_5(s) = delta H^0_r times n = -579 KJ \r\n AS volume of solution = 250ml d = 1.25 gm/ml (because d = m/v) therefore m = d times V therefore mass = 1.25 times 250ml