[Unit 4] Chemical Reactions

This question is based on the following reaction.

MnO41-(aq) + 5Fe2+(aq) + 8H1+(aq) -> 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

a) Is this reaction an oxidation-reduction reaction? Justify your response by identifying the oxidation states for manganese (Mn).
b) An sample of unknown concentration of potassium permanganate (KMnO4) is titrated with 25.0 mL of 1.25 M iron (II) nitrate (Fe(NO3)2). If the volume of potassium permanganate that was titrated is 12.7 mL, what is its concentration?
c) In a separate reaction, sodium hydroxide (NaOH) it used to standardize the iron (II) nitrate.

2NaOH(aq) + Fe(NO3)2(aq) -> Fe(OH)2(s) + 2NaNO3(aq)

If 40.0 mL of 0.95 M NaOH reacts with 31.0 mL of 0.65 M Fe(NO3)2, then what mass of the precipitate forms?
d) What are three major ions that remain in the filtrate?

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Side Note: I used a whiteboard but I wouldn’t for the test, I was just too lazy to get out paper :crazy_face:

Solutions
a) The oxidation state for Mn in MnO41- is +7. The oxidation state for Mn in Mn2+ is 2+. The oxidation state for manganese change, therefore, this is a redox reaction.
b)


c)

d) First, the spectator ions are Na1+ and NO31-. They do not participate in the reaction and remain dissolved in solution. The third ion is Fe2+. It is part of the excess reactant and while a majority of it ends up in the precipitate, some remains dissolved in solution.

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