Question

Consider the following oxides: 
V_2O_5, Cr_2O_3, Mn_2O_7, V_2O_3, VO_2 
A number of oxides which are acidic is \( x \). 
Consider the following complex compound: 
[Co(NH_2CH_2CH_2NH_2)_3](SO_4)_3 
The primary valency of the complex is \( y \). 
What is the value of \( x + y \) is?

Hint:

When dealing with complex compounds, the primary valency is determined by the number of directly coordinated ions or ligands around the central metal ion.

Answer 1

We are given the following oxides: \( V_2O_5, Cr_2O_3, Mn_2O_7, V_2O_3, VO_2 \). We need to determine which of these oxides are acidic.
- \( V_2O_5 \): This is an acidic oxide because it forms \( H_2VO_3 \) when dissolved in water.
- \( Cr_2O_3 \): This is a basic oxide as it is amphoteric but tends to show basic behavior in general.
- \( Mn_2O_7 \): This is an acidic oxide because it forms \( H_2MnO_4 \) when dissolved in water.
- \( V_2O_3 \): This is an amphoteric oxide, but it can act as an acidic oxide under certain conditions.
- \( VO_2 \): This is an acidic oxide.
Thus, the acidic oxides are \( V_2O_5, Mn_2O_7, VO_2 \), giving us \( x = 3 \). Now, consider the complex \( [Co(NH_2CH_2CH_2NH_2)_3](SO_4)_3 \), where the ligand \( NH_2CH_2CH_2NH_2 \) is ethylenediamine (en). In this complex, ethylenediamine is a bidentate ligand, coordinating through two lone pairs. The primary valency \( y \) corresponds to the number of ions that the metal ion coordinates with directly. As there are three ethylenediamine ligands, the primary valency \( y \) is 3. Thus, the value of \( x + y = 3 + 3 = 6 \).