Reaction of Sodium Metal and Water

[Qube]

Homework Statement

When sodium is dropped into water, aqueous sodium hydroxide and hydrogen gas are produced. Which of the following are correct regarding this reaction?

1) Sodium metal is the reducing agent.
2) There are no spectator ions.
3) In the balanced net ionic equation, all coefficients are unity.
4) The electrical conductivity of the aqueous part increases during the reaction.

Homework Equations

Oxidation is loss of electrons. Reduction is gain of electrons. Reducing agents give electrons. Oxidizing agents take electrons.

Unity = 1.

The Attempt at a Solution

1) Sodium metal starts with an oxidation number of 0 since it's by itself (in its elemental form). On the product side however sodium in NaOH has a +1 oxidation state. Sodium has been oxidized; it has lost electrons. Sodium has given up electrons to the oxygen and hydrogen too, so sodium is a reducing agent. Not all elements that have been oxidized are reducing agents, correct?

2) I'm not seeing many ions except the ions that form on the product side of the equation, so there can't be any spectator ions, since spectator ions are defined to exist as reactants and as products.

3) There isn't a net ionic equation because the only ions are on the product side of the equation.

4) Yes, aqueous sodium hydroxide is produced, and it is an electrolyte.

So I conclude that yes, Na metal acts as a reducing agent, having reduced the oxygen and hydrogen by giving them an electron; that yes, there are no spectator ion; that yes, the electrical conductivity of the solution increases as electrolytes are formed. Is my reasoning all correct?

 

[Borek]

Looks OK to me.

I admit I don't like some of these questions. They are nitpicky without adding any value.

 

[Qube]

Great! But are all elements which are oxidized also reducing agents?

 

[Borek]

Great! But are all elements which are oxidized also reducing agents?

In the particular reaction they were oxidized - yes.. Doesn't mean they are reducing agent in general.

Hydrogen peroxide - which is a known oxidizing agent - is sometimes a reducing agent. Compare titrations.info/permanganate-titration-hydrogen-peroxide

 

[DeeNos]

Your reasoning is mostly correct, but there are a few points that could use clarification:

1) Sodium is indeed a reducing agent in this reaction, as it loses electrons and reduces the oxidation state of oxygen and hydrogen. However, it is important to note that not all elements that are oxidized are reducing agents. For example, in a reaction where oxygen is reduced to water, oxygen is not considered a reducing agent because it is not actively giving electrons to another species. In the case of sodium, it is actively giving electrons to oxygen and hydrogen, making it a reducing agent.

2) You are correct that there are no spectator ions in this reaction, as all the ions present are involved in the reaction. However, it is worth noting that spectator ions can exist in both reactants and products, as long as they are not involved in the actual chemical reaction. In this case, since there are no ions present in the reactants, there cannot be any spectator ions.

3) There is a net ionic equation for this reaction, which is: 2Na + 2H2O → 2NaOH + H2. The net ionic equation only includes the species that are actively participating in the reaction, in this case, sodium and water.

4) Yes, the electrical conductivity of the solution will increase as electrolytes are formed. However, it is important to note that the electrical conductivity is not solely due to the presence of sodium hydroxide, but also due to the presence of dissolved sodium ions and hydroxide ions, which are also present in the solution.