According to the vsepr model, the progressive decrease in the bond angles in the series of molecules ch₄, nh₃, and h₂o is best accounted for by the

lone pair-bond pair repulsion is best accounted for decrease in bond angle

Explanation:

Bond angle in each compounds depends on presence of lone pair on central atom.

In , there is no lone pair on C atom. So, no lone pair-bond pair repulsion is present here. Hence is

In , there is one lone pair on N atom. So, one lone pair-bond pair repulsion is present here. Hence is

In , there are two lone pairs on O atom. So, two lone pair-bond pair repulsion are present here. Hence is

So, lone pair-bond pair repulsion is best accounted for decrease in bond angle

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.

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.