Question

Section Provide a test (including reagents needed and what to look for if it gives a positive result), and the ner ionic equation for the test used, to distinguish berween the following compounds NICI, or BaCl NaC,H,O, or KSCN: ZnS or CuS AgCl or Ag,O MgCO, or BaSO 27 LA

Answer 1

1) The addition of any soluble sulfate salt will allow us to differentiate between BaCl₂ (a white precipitate of BaSO₄) and NiCl₂ (NiSO₄ is soluble in water):

$Ba^{2+}_{(aq)}+SO_{4,(aq)}^{2-}\rightarrow BaSO_{4,(s)}$

2) The addition of Fe(III) ions (in the form of FeCl₃) for example would allow the differentiation of KSCN (by the formation of FeSCN²⁺, which has a strong red color) and NaC₂H₃O₂, which would not yield any color:

$Fe^{2+}_{(aq)}+SCN_{(aq)}^{-}\rightarrow FeSCN_{(aq)}^{2+}$

3) Of these, ZnS is white and CuS is black... so they are pretty easy to identify. Theur dissolution an strong acid should yield a blue solution in the case of CuS and an uncolored solution for ZnS:

$CuS_{(s)}+2H^{+}_{(aq)}\rightarrow H_{2}S_{(g)}+Cu^{2+}_{(aq)}$

4) Again, AgCl is a white solid and Ag₂O is a black solid, both insoluble in water . Upon addition of nitric acid, only Ag₂O will dissolve:

$Ag_{2}O_{(s)}+2HNO_{3,(aq)}\rightarrow 2Ag^{+}_{(aq)}+NO_{3,(aq)}^{-}+H_{2}O_{(l)}$

5) MgCO₃ will generate bubbles due to the formation of CO₂ upon the addition of an acid, while BaSO₄ won't:

$MgCO_{3}_{(s)}+2H^{+}_{(aq)}\rightarrow CO_{2,(g)}+H_{2}O_{(l)}+Mg_{(aq)}^{2+}$