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

The provided oxides are \( V_2O_5, Cr_2O_3, Mn_2O_7, V_2O_3, VO_2 \). Acidic oxides among these are identified as follows:
- \( V_2O_5 \) is acidic, forming \( H_2VO_3 \) in water.
- \( Cr_2O_3 \) is primarily basic, despite amphoteric properties.
- \( Mn_2O_7 \) is acidic, forming \( H_2MnO_4 \) in water.
- \( V_2O_3 \) is amphoteric and can exhibit acidic behavior.
- \( VO_2 \) is acidic.
Consequently, the acidic oxides are \( V_2O_5, Mn_2O_7, VO_2 \), resulting in \( x = 3 \).
Next, consider the complex \( [Co(NH_2CH_2CH_2NH_2)_3](SO_4)_3 \), where \( NH_2CH_2CH_2NH_2 \) (ethylenediamine, en) acts as a bidentate ligand through its two lone pairs.
The primary valency \( y \) is determined by the number of directly coordinated metal ions. With three ethylenediamine ligands, the primary valency \( y \) is 3.
Therefore, \( x + y = 3 + 3 = 6 \).