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Two reactions are given below: 2Fe(s) + 32O2(g) Fe2O3(s), H = -822 kJ/mol C(s) + 12O2(g) CO(g), H = -110 kJ/mol Then enthalpy change for following reaction 3C(s) + Fe2O3(s) 2Fe(s) + 3CO(g) is kJ/mol.
492
Hess's law: required reaction = 3 × (ii) − (i)
H = 3(-110) - (-822)
= -330 + 822
= +492 kJ/mol
Answer: 492
Which of the following is not correct?
Standard enthalpy of vapourisation for CCl4 is 30.5 kJ mol-1. Heat required for vapourisation of 284 g of CCl4 at constant temperature is kJ. (Given molar mass in g mol-1; C = 12, Cl = 35.5)
If three moles of an ideal gas at 300 K expand isothermally from 30 dm3 to 45 dm3 against a constant opposing pressure of 80 kPa, then the amount of heat transferred is J.
For a certain thermochemical reaction M N at T = 400 K, = 77.2 kJ mol-1, = 122 J K-1, log equilibrium constant (log K) is − 10-1.