November 10, 2024, 02:42:49 PM
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Topic: calculation from a neutralization reaction and balancing ox-red reactions -_-;;  (Read 4763 times)

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Offline imari

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I have two questions that I am struggling with.

1. When 50.0 mL of a certain Na2CO3 solution was combined with 0.102 M HCl, 56.3 mL of HCl were required for complete neutralization, according to the equation:

                             CO32- + 2H+ --> CO2 +H2O

Calculate the number of grams of CaCO3 that would be precipitated if an excess of CaCl2 were added to a separate 50.0 mL portion of the Na2CO3 solution.


I did work for this and got an answer but I am not sure if it is correct:

0.102 mol/L * 0.0563 L = 0.00574 mol HCL

0.00574 mol H * 1/2 = 0.00287 mol CO3

Since Ca2+ + CO32- --> CaCO3

0.00287 mol CaCO3 * 100 g/mol = 0.287g CaCO3



2. Balance the following oxidation-reduction equations:

a) Zn + NaNO3 + NaOH --> Na2ZnO2 + NH3 + H2O

First I split them up into two half reactions and then balanced them but the electrons and charges confused me so i am not sure if i did it right.

oxidation: Zn + 2NaOH --> Na2ZnO2 + H+ + 2e-
reduction: 2e- + 9H+ + NaNO3 --> NH3 + 3H2O + Na+

Then I added both the right sides and then both the left sides, without writing the two electrons on both sides. Are the half reactions correct?

b) MnSO4 + (NH4)2S2O8 + H2O --> MnO2 + H2SO4 + (NH4)2SO4

It looks to me that the Mn is oxidized and the S is reduced but when I try to write the half reactions, I am having trouble balancing them. How do I write the half reactions?

Offline Borek

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0.00287 mol CaCO3 * 100 g/mol = 0.287g CaCO3

Correct :)

Quote
2. Balance the following oxidation-reduction equations:

First of all - write them in net ionic form, this way it is easier to concentrate on what is going on.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline AWK

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1. OK
2
Quote
oxidation: Zn + 2NaOH --> Na2ZnO2 + H+ + 2e-
reduction: 2e- + 9H+ + NaNO3 --> NH3 + 3H2O + Na+
Be more careful when balancing half reaction - atoms and cherges should be balanced
oxidation: Zn + 2NaOH --> Na2ZnO2 + 2H+ + 2e-
reduction: 8e- + 9H+ + NaNO3 --> NH3 + 3H2O + Na+
Show your attempt for 3
AWK

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