Question

the precipitate formed when ni(no₃)₂ is mixed with li₂s is
answer:
a. ni₂s
b. nis
c. lino₃
d. li₂no₃

Explanation:

Step1: Write the chemical reaction

When $\text{Ni(NO}_3)_2$ reacts with $\text{Li}_2\text{S}$, a double - displacement reaction occurs. The general form of a double - displacement reaction is $AB + CD
ightarrow AD+CB$. Here, $A = \text{Ni}^{2 +}$, $B=\text{NO}_3^-$, $C = \text{Li}^+$, and $D=\text{S}^{2 -}$. The reaction is $\text{Ni(NO}_3)_2+\text{Li}_2\text{S}
ightarrow\text{NiS}+2\text{LiNO}_3$.

Step2: Determine the precipitate

According to solubility rules, most nitrates ($\text{NO}_3^-$) are soluble in water. Lithium nitrate ($\text{LiNO}_3$) is soluble. Sulfides ($\text{S}^{2 -}$) of most transition metals are insoluble. Nickel sulfide ($\text{NiS}$) is insoluble in water and will precipitate out.

Answer:

B. NiS