For each reaction, identify another quantity that is equal to Δ H ∘ rxn . CH 4 ( g ) + 2 O 2 ( g ) ⟶ CO 2 ( g ) + 2 H 2 O ( l ) enthalpy of formation of CO 2 ( g ) − 4 × bond energy of C − H 4 × bond energy of C − H enthalpy of combustion of CH 4 CH 4 ( g ) ⟶ C ( g ) + 4 H ( g ) 4 × bond energy of C − H − 4 × bond energy of C − H enthalpy of formation of C ( g ) enthalpy of combustion of CH 4 C ( graphite ) + 2 H 2 ( g ) ⟶ CH 4 ( g ) enthalpy of combustion of CH 4 4 × bond energy of C − H − 4 × bond energy of C − H enthalpy of formation of CH 4 ( g ) C ( g ) + 4 H ( g ) ⟶ CH 4 ( g ) − 4 × bond energy of C − H enthalpy of formation of CH 4 ( g ) enthalpy of combustion of C 4 × bond energy of C − H

Explanation:

CH 4 ( g ) + 2 O 2 ( g ) ⟶ CO 2 ( g ) + 2 H 2 O ( l )

enthalpy of formation of CO 2 ( g )

− 4 × bond energy of C H

4 × bond energy of C − H

enthalpy of combustion of CH 4

enthalpy of combustion of CH 4: This is because we usually calculate the enthalpy change of combustion from enthalpies of formation. This is given as;

ΔHoc = ∑ΔH∘f(products) − ∑ΔH∘f(reactants)

CH 4 ( g ) ⟶ C ( g ) + 4 H ( g )

1. enthalpy of combustion of CH4

2. enthalpy of formation of C(g)

3. 4× bond energy of C–H

4. –4× bond energy of C–H

4× bond energy of C–H: Bond breaking is an endothermic process. So it cannot be option 4, enthalpy of formation of a pure element is 0 KJ/mol. This is not a combustion reaction, so options 1 and 2 are aslo wrong.

c) C(graphite) + 2H2(g) CH4(g)

1. enthalpy of combustion of CH4

2. enthalpy of formation of CH4(g)

3. 4× bond energy of C–H

4. –4× bond energy of C–H

The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements. The correct option is; enthalpy of formation of CH4(g)

d) C(g) + 4H(g) CH4(g)

1. enthalpy of combustion of C

2. enthalpy of formation of CH4(g)

3. 4× bond energy of C–H

4. –4× bond energy of C–H

–4× bond energy of C–H; bond formation is always exothermic, it cannot be option 3. This is not a combustion reaction so it cannot be option 1.  enthalpy of formation of a pure element is 0 KJ/mol, so it cannot be option 2.

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.

i think it's letter a.