Carbon monoxide and hydrogen react over a catalyst to produce methanol. At 5-10
ID: 1069632 • Letter: C
Question
Carbon monoxide and hydrogen react over a catalyst to produce methanol. At 5-10 MPa (50-100 atm) and 250 degree C, it can catalyze the production of methanol from carbon monoxide and hydrogen with high selectivity (>99.8%): CO + 2 H_2 rightarrow CH_3OH Describe the chemical bonding and the geometry of the methanol molecule. Write the balanced chemical reaction equation for complete combustion of methanol. When 1.922 g of methanol is burned in a constant-volume bomb calorimeter, the energy, 43.68 kJ, is liberated. Calculate the heat of combustion of methanol in kJ/mol. Calculate the standard enthalpy of reaction in kJ/mol for combustion of methanol given that the standard enthalpy of formation. Delta H_f degree, for carbon dioxide, water and methanol is: -393.5 kJ/mol, -285.8 kJ/mol and -238.4 kJ/mol, respectively. Comment on the difference between the results in c) and d). The dipole moment of methanol is 1.69 D. Write the definition of dipole moment. Explain why the methanol molecule could be dipolar and decide whether it could be miscible with water or not.Explanation / Answer
2. CH3OH + 2O2--->CO2+ 2H2O
3. moles of methanol in 1.922 gm = mass/molar mass = 1.922/32 = 0.060
Heat of combustion = 43.68/0.060=728 Kj/mole
4. standard enthalpy = 2* standard enthalpy of H2O+ 1* standard enthalpy of CO2-{ 1* standard enthalpy of CH3OH + 2* standard enthalpy of O2}
Standard enthalpy of O2 is since =0, 2, 1,1 and 2 are stoichiometric coefficients of H2O.CO2, CH3OH and O2.
standard enthalpy= 2*(-285.8)+(-393.5)- {238.4}=-726.7 Kj
5. Dipole moment is product of the separation of the ends of a dipole and the magnitude of the charges.
Methanol is dipolar due to electronegativity difference between O and H. Electronegativity of O is 3.5 while that for Hydrogen is 2.1. This gives rise to partial negative charge on O and partial positive charge on H. Hence dipole moment.
water interacts with hydroxide groups of methnol leading to their miscibility.