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Reaction of Sodium Metal and Water

  1. Dec 3, 2013 #1

    Qube

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    Gold Member

    1. The problem statement, all variables and given/known data

    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.

    2. Relevant equations

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

    Unity = 1.

    3. 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?
     
  2. jcsd
  3. Dec 3, 2013 #2

    Borek

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    Staff: Mentor

    Looks OK to me.

    I admit I don't like some of these questions. They are nitpicky without adding any value.
     
  4. Dec 3, 2013 #3

    Qube

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    Gold Member

    Great! But are all elements which are oxidized also reducing agents?
     
  5. Dec 3, 2013 #4

    Borek

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    Staff: Mentor

    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
     
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