Please help me to answer these questions. tell me clearly how to do them.thank you so much bud's?

Question

1. True or False: The rate of a chemical reaction is directly related to the number of collisions that occur between reactant molecules.

2 Water molecules are polar molecules (that is they have a dipole moment). This results in which of the following propertes of water? Most ionic materials dissolve in water.

Water has a high boiling point.

Both are true

Neither are true.

Proceeding down the Noble Gas column on the periodic table, the melting and boiling points of the noble gas elements increases. Neon has higher melting and boiling points than Helium and Krypton has higher melting and boiling points than Neon etc. This shows which of the following:

The nature of ionic bonds

London Dispersion Forces are stronger between larger diameter atoms whose valence electrons are farther from the nucleus and not as tightly bound.

Hydrogen bonds

No other answers are correct

Answer 1

1. True.  This is the basis of the collision theory of kinetics -- in order for a reaction to occur, reactants need to collide with each other in very specific ways ("effective collisions").  More collisions = more collisions that are effective = higher observed rxn rate.

2. Question's not worded as well as I would like, but I'll explain it anyway.

As far as I know, in the covalent compound world, water's BP is not that low for a molecule of its size. This IS related to its being a polar molecule.  Specifically, water exhibits hydrogen bonding -- which is a type of interaction/ (intermolecular force) that involves a (slightly positive) hydrogen atom of one water molecule interacting with a (slightly negative) oxygen atom of another water molecule.  Looks kind of like an ionic bond, but much weaker.

What does this mean?  The process of boiling breaks up interactions between neighboring molecules.  Hydrogen bond type interactions take more energy to break up than, say, London Dispersion Forces.  More energy for breaking up interactions = higher melting/ boiling points.  As an example, N2, which does not exhibit hydrogen bonding, has a MUCH lower melting and boiling points.

With a dipole moment comes slight (electrical) charges.  Many ionic solids do very well with this -- in fact, when an ionic solid is put into water, individual ions are surrounded by water molecules that are attracted to the electrical charge.  The ionic solid breaks up into ions in water, and we see this as being "dissolved."

3. Noble gases do not bond in most cases.  London Dispersion forces are all we can talk about here - and the description looks correct.  Remember your periodic trends?  It's like you (an electron) being at summer camp 300 miles away from home -- how well, really, can your parents (nucleus) control you?  This is, by the way, called shielding.  

I won't write a whole description of how LDF works here, because it gets complicated -- but if you're interested, email me off list.

Answer 2

1) True because a reaction cannot occur unless the reactants come into contact with one another, so more collisions=more tiny reactions taking place.

2) Like dissolves like and water is not ionic so most ionic materials wouldn't dissolve in water.  Polar covalent bonds are not exceptionally strong, so water doesn't have a high boiling point, so neither are true.

3)Ionic and H-bonding has nothing to do with the properties of pure noble gases.  The part about London Dispersion forces is true