Question

A compound is made by mixing cobalt (III) nitrite solution and potassium nitrite solution in the ratio of 1:3. The aqueous solution of the compound showed 4 particles per molecule whereas molar conductivity reveals the presence of six electrical charges. The formula of the compound is:

A.\[Co{{(N{{O}_{2}})}_{3}}.2KN{{O}_{2}}\]  

B.\[Co{{(N{{O}_{2}})}_{3}}.3KN{{O}_{2}}\]

C.\[{{K}_{3}}[Co{{(N{{O}_{2}})}_{6}}]\]

D.\[K[Co{{(N{{O}_{2}})}_{4}}]\]

Answer 1

Hint: The molar conductivity is defined as the conductivity of the solution of the electrolyte which has been divided by the molar concentration of the electrolyte. It tends to measure the efficiency of the electrolyte given which tends to conduct the electricity in the solution. The coordination compounds are defined as the compounds which tend to possess one or more metal centres which are bound to the ligands.

Complete step by step answer:

The formula of the cobalt (III) nitrite solution is \[Co{{(N{{O}_{2}})}_{3}}\] and the formula for potassium nitrite is \[KN{{O}_{2}}\]. So the question says that these two solutions are being reacted in the ratio of 1:3. This means 1 mole of cobalt nitrite has been reacted with 3 moles of potassium nitrite. So look at the following reaction:

\[Co{{(N{{O}_{2}})}_{3}}+KN{{O}_{2}}\to {{K}_{3}}[Co{{(N{{O}_{2}})}_{6}}]\]

So as in the question it is written that the molar conductivity reveals the presence of six electrical charges. So let us check in the formed compound. The dissociation of the formed compound is: \[{{K}_{3}}[Co{{(N{{O}_{2}})}_{6}}]3{{K}^{+}}+C{{o}^{3+}}+6N{{O}_{2}}^{-}\] 

So here we see that the total positive charge is 6, that is 3 positive charges are present on potassium and 3 positive charges on cobalt which makes 6 and the total negative charge is 6 as there are 6 moles of nitrogen dioxide. So this confirms that the molar conductivity in the formed compound shows six electrical charges.

So, the correct answer is option C.

Note: The  Iupac name for the \[{{K}_{3}}[CO{{(N{{O}_{2}})}_{6}}]\] is potassium hexanitritocobaltate(III). It is also known as the Indian yellow. It is a salt. This complex has the charge -3. As the six nitrate molecules are present so it is hexanitrito and as the charge is negative on the compound so the name ends with ‘-ate’.