Question

30. Calculate the standard enthalpy of formation for

nitromethane, CH3NO2, using its enthalpy of combustion: 2 CH3NO2(l)
+ O2(g) → 2 CO2(g) + 3 H2O(l) + N2(g) ΔH˚ = –1418 kJ ΔHf˚ for

Answer 1

The standard enthalpy of formation for nitromethane (CH3NO2) is -857.4 kJ/mol.

Step-by-step explanation:

To calculate the standard enthalpy of formation for nitromethane (CH3NO2), we can use Hess's Law and the enthalpy of combustion reaction provided.

The enthalpy of combustion reaction is:

2 CH3NO2(l) + 3/2 O2(g) → 2 CO2(g) + 3 H2O(l) + N2(g) ΔH˚ = -1418 kJ

First, we need to balance the equation by multiplying the enthalpy of combustion reaction by a factor of 2:

4 CH3NO2(l) + 3 O2(g) → 4 CO2(g) + 6 H2O(l) + 2 N2(g) ΔH˚ = -2836 kJ

Next, we can use the balanced equation to determine the enthalpy of formation for nitromethane. Since the enthalpy of formation for elements in their standard states is defined as zero, we can subtract the enthalpy of combustion from the enthalpy of formation for the products:

ΔHf˚(CH3NO2) = [ΔH˚(CO2) + 3 ΔH˚(H2O) + ΔH˚(N2)] - [4 ΔH˚(CH3NO2) + 3 ΔH˚(O2)]

Substituting the known values:

ΔHf˚(CH3NO2) = [0 + 3(-285.8 kJ/mol) + 0] - [4(-2836 kJ/mol) + 3(0)]

ΔHf˚(CH3NO2) = -857.4 kJ/mol

Therefore, the standard enthalpy of formation for nitromethane (CH3NO2) is -857.4 kJ/mol.

The complete question is

Calculate the standard enthalpy of formation for nitromethane, CH3NO2, using its enthalpy of combustion:

2 CH3NO2(l) +