Which will have the lowest boiling point?

a.

pure water

b.

0.5 m nacl (aq)

c.

1.0 m nacl (aq)

d.

2.0 m nacl (aq)

A.   pure water

Explanation:

= change in boiling point

i = Van'T Hoff factor  

= freezing point constant

m = molality

1. For pure water

, i= 1 as it is a non electrolyte and does not dissociate.

2. For

, i= 2 , as it is a electrolyte and dissociate to give 2 ions and concentration will be (0.5+0.5)=1M[/tex]

3. For

, i= 2 , as it is a electrolyte and dissociate to give 2 ions and concentration will be (1+1)=2M[/tex]

4. For

, i= 2 , as it is a electrolyte and dissociate to give 2 ions and concentration will be (2+2)=4M[/tex]

Thus as vant hoff factor is lowest for pure water and thus the boiling point will be lowest.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.