A solution is known to contain either Ni2 or Cr3 . Addition of what single (1 only) reagent would identify which ion is present?

Chemistry

1 answer:

galina1969 [7]3 years ago

6 0

Answer:

Explanation:

From the periodic table; both elements given are from the same group 3.

To test for which ion will be present in the experiment;

We added 6M aqueous sodium hydroxide in excess.

This process is followed by the addition of hydrogen peroxide H2O2 while stirring.

Heat is then applied to the solution.

After we've carried out those process;

We will notice the following;

If $Ni^{2+}$ is present, then a green $NI(OH)_2$ precipitate will be formed

If $Cr^{3+}$ is present,then a yellow-colored $CrO^{2-}_{4}$ will be formed.

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Explanation:

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In this case, since the modelling of titration problems can be approached via the Henderson-Hasselbach equation to set up a relationship between pH, pKa and the concentration of the acid and its conjugate base, we can write:

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Whereas the pH is given as 3.14 and the concentrations are the same, that is why the pH would be equal to the pKa as the logarithm gets 0 (log(1)=0); thus, we can calculate the Ka via:

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