Chapter 3, Problem 3.29CP

In the following drawings, red spheres represent cations and blue spheres represent anions. Match each of the drawings (a)–(d) with the following ionic compounds:

1. (i) Ca₃(PO₄)₂
2. (ii) Li₂CO₃
3. (iii) FeCl₂
4. (iv) MgSO₄

Interpretation Introduction

Interpretation:

For the given compounds correct representation of diagramhas to be chosen.

Explanation of Solution

To choose: Correct representation of diagram for given compounds.

Given,

${\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}}\text{)}}_{\text{2}}\text{,}{\text{Li}}_{\text{2}}{\text{CO}}_{\text{3}}\text{,}{\text{FeCl}}_{\text{2}}\text{and}{\text{MgSO}}_{\text{4}}$

Figure 1

Consider red sphere as cation and blue sphere as anion.

${\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}}\text{)}}_{\text{2}}$:

The ratio of cation (${\text{Ca}}^{\text{2+}}$) and anion (${\text{PO}}_{\text{4}}{}^{\text{3-}}$ ) is $3:2$. There are $18$ red sphere and $12$ blue spheres are in diagram d which means they are in $3:2$. Hence, ${\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}}\text{)}}_{\text{2}}$ matches diagram d.

${\text{Li}}_{\text{2}}{\text{CO}}_{\text{3}}$:

The ratio of cation (${\text{Li}}^{\text{+}}$) and anion (${\text{CO}}_3{}^{\text{2-}}$ ) is $2:1$. There are $12$ red sphere and $6$ blue spheres are in diagram b which means they are in $2:1$. Hence, ${\text{Li}}_{\text{2}}{\text{CO}}_{\text{3}}$ matches diagram b.

${\text{MgSO}}_{\text{4}}$:

The ratio of cation (${\text{Mg}}^{\text{2+}}$) and anion (${\text{SO}}_{\text{4}}{}^{\text{2-}}$ ) is $1:1$.  There are $12$ red sphere and $12$ blue spheres are in diagram a which means they are in $1:1$. Hence, ${\text{MgSO}}_{\text{4}}$ matches diagram a.

${\text{FeCl}}_{\text{2}}$:

The ratio of cation (${\text{Fe}}^{\text{+}}$) and anion (${\text{Cl}}^{\text{-}}$ ) is $1:2$. There are $6$ red sphere and $12$ blue spheres are in diagram c which means they are in $1:2$. Hence, ${\text{FeCl}}_{\text{2}}$ matches diagram c.

Conclusion

For the given compounds correct representation of diagram was chosen.