How many grams of hydrogen are in "69" g of ch4o?

             8.62 g of Hydrogen

Solution:

Molar mass of CH₄O (Methanol) is 32 g.mol⁻¹.

It means,

                  32 g of CH₄O contains  =  4 g of Hydrogen

Then,

             69 g of CH₄O will contain  =  X g of Hydrogen

Solving for X,

                    X  =  (69 g × 4 g) ÷ 32 g

                    X  =  8.62 g of Hydrogen

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.