[bookworm]

i) the pH of aqueous NH4NO3 is less than 7

is it because
NH4NO3  NH4+  + NO3- (don't undergo salt hydrolysis)

NH4+  +  H2O  NH3 + H3O+
.:. the solution is acidic, therefore it is less than 7

ii)the pH at the end point in the titration of ethanoic acid (CH3COOH) with sodium hydroxide (NaOH) is greater than 7

is it because there is an excess of NaOH
whereby, NaOH    Na+  + OH-

iii) the pH of 1*10^-3 M HF is not 3

[Borek]

NH₄⁺ is a weak acid.

Equivalence point is when you mix stoichiometric amount of titrant and titrated substance, so you can't have exess NaOH. What do you know about CH₃COO^-?

[bookworm]

CH3COO-Na+    CH3COO-  + Na+ (does not undergo salt hydrolysis)

CH3COO- + H2O  CH3COOH + OH-

[Borek]

CH3COO-Na+    CH3COO-  + Na+ (does not undergo salt hydrolysis)

CH3COO- + H2O  CH3COOH + OH-

You see where the high pH comes from?

You don't have to write dissociation reaction each time for reagents that are fully dissociated from the very beginning (like NaOH, HCl, NaF, CH₃COONa and so on).

[bookworm]

it comes from the base?

[Borek]

Please elaborate.

[bookworm]

im lost 

[Borek]

Just try to give more details.