i have exam asap plz Given the following reaction Calculate the standard enthalp

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i have exam asap plz

Given the following reaction Calculate the standard enthalpy of formation of CuO(3) 155 kJ -155 kJ -299 kJ +299 kJ None of the above. The specific heat capacity of iron (Fe) is 0.45 g. Calculate the molar heat capacity of iron. 8.0 times 10^-3 J c, mol 8.0 J C, mol 25.1 times 10^-2 j C, mol 2.51 times 10^-2 J C, mol None of the above A gas of unknown identity effuses at a rate of 83.3 ml. per second. A second gas whose molar mass is 44.0 g effuses at a rate of 0.102 L per second. The molar mass of first gas is 98.5 g/mol 66.0 g/mol 126 g/mol 42.0 g/mol None of the above

Explanation / Answer

4) I3- + 2e- -------> 3I-
   3I = -1 ; I = -1/3
Option e is the answer.

5) Cu(s) + 1/2O2(g) ----> CuO(s)
Enthalpy of formation is the heat emitted to form one molecule of CuO(s) from its reactants.
To get the above equation we must rearrangethe given equations to form,
Cu2O(s) + (1/2)O2(g) -----> 2CuO(s) ; H° = -288 / 2 = -144 kJ
Cu(s) + CuO(s) -------> Cu2O(s) ; H° = -11 kJ
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Cu(s) + 1/2O2(g) ----> 2CuO(s) ; H°f  = -144-11 = -155 kJ
Option b is the answer

6) 0.45 J / (1 gm / 55.845 gm/mol) * oC = 25.13025 J / mol oC
Option C is the answer

7) According to Graham's law rate of effusion of gas is inversely proportional to square root of its
   molecular weight.
   102 / 83.3 = M / 44
   ( 102 / 83.3 )2 * 44 = M
   M = 65.9725 gm/mol = 66 gm/mol approx.
Option b is the answer

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