Problem 7.1

1. In (i) What takes priority Electron transfer or Electronegative/Positive element ?

2. In (i) Explain addition of Electronegative/Positive element seen as oxidation

3. In (iii) How can Na be oxidized when hydrogen is been added to it ?

1 hour ago, HbWhi5F said:

Problem 7.1

1. In (i) What takes priority Electron transfer or Electronegative/Positive element ?

2. In (i) Explain addition of Electronegative/Positive element seen as oxidation

3. In (iii) How can Na be oxidized when hydrogen is been added to it ?

What are your initial thoughts about this?

@exchemist

1. In (i) What takes priority Electron transfer or Electronegative/Positive element ?

I think more electronegative is a good oxidant

2. In (i) Explain addition of Electronegative/Positive element seen as oxidation

When the other atoms is more electronegative it is oxidized

3. In (iii) How can Na be oxidized when hydrogen is been added to it ?

This part is wierd hydrogen being added is reduced.

3 hours ago, HbWhi5F said:

@exchemist

1. In (i) What takes priority Electron transfer or Electronegative/Positive element ?

I think more electronegative is a good oxidant

2. In (i) Explain addition of Electronegative/Positive element seen as oxidation

When the other atoms is more electronegative it is oxidized

3. In (iii) How can Na be oxidized when hydrogen is been added to it ?

This part is wierd hydrogen being added is reduced.

Yeah I think that's the right idea. In H₂S, the nominal oxidation state of S is -2 and H is +1. In effect you are pretending the compound is ionic, even thought it is covalent, giving a +ve oxidation number to the more electropositive atom and a -ve state to the more electronegative. Cl, being in elemental form, has an oxidation number of 0. After the reaction, H is still +1, but Cl is now -1 and S has gone from -2 to 0. So one can say that Cl has been reduced, whereas S has been oxidised and H has not changed. So H₂S overall has been oxidised by Cl₂. Something similar will go for the rest of them.

And you are right NaH is a bit weird. But Na is more electropositive than H. This compound is called sodium hydride. It is in fact ionic and contains an actual anion of H, the hydride ion, H-. This has 2 valence shell electrons, making it isoelectronic with helium. Needless to say this compound is pretty reactive.

Oxidation numbers are a bit of a strange convention in chemistry that takes some getting used to. Your problem 7.3 is easier in that you have some obvious metals that will have +ve oxidation states and obvious halide or oxide partners that will be -ve.

@exchemist thanks alot