Justify why the bond angles for BH3 are greater than the bond angles for NH3

Explanation:

Bond angles in BH3 are greater than the bond angles for NH3 because BH3 have three electron clouds that bond to one central atom Boron. Each clods have electrons that bond between Boron and Hydrogen atom. The three electrons cloud attach to Central atom B and adopt a position which make them to form triagonal planar geometry making the angles between them to be bigger.

But as for NH3, it has extra lone pairs making it four electron clouds which form tetrahedral geometry. The extra lone pair occupy space making the angles between the bond to be reduced.

c.

explanation:

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.