Precipitation Reactions (4.2.1)

Question 1

• A precipitation reaction occurs when substances in solution react to form a solid insoluble salt.

Answer 1

• A precipitation reaction occurs when substances in solution react to form a solid insoluble salt.

Question 2

• A solubility table helps in predicting the solubility of a salt.

Answer 2

• A solubility table helps in predicting the solubility of a salt.

Question 3

A precipitation reaction occurs when substances in solution react to form a solid insoluble salt. This salt is called a precipitate. For example, when a solution of lead(II) nitrate (Pb(NO3)2) is mixed with a solution of potassium iodide (KI), a yellow precipitate forms. This precipitate is lead(II) iodide (PbI2). Since potassium ion and nitrate ion do not take part in the precipitation reaction, they are not shown in the net ionic equation. Ions which do not take part in a reaction are called spectator ions. A solubility table helps in predicting the solubility of a salt. Problem: What is the precipitate when a solution of nickel(II) nitrate (Ni(NO3)2) is mixed with a solution of sodium carbonate (Na2CO3)? First, identify the ions in the solution (Ni2+, NO3–, Na+, and CO32–). Second, check a solubility table for information on these ions. Compounds containing alkali metal ions such as
sodium ion (Na+) tend to be soluble, so sodium ion will not precipitate. Compounds containing nitrate ion (NO3) also tend to be soluble, so nitrate ion will not precipitate.
However, compounds containing carbonate ion (CO3
2–) tend to be insoluble. Therefore, the precipitate is nickel(II) carbonate (NiCO3).

Answer 3

A precipitation reaction occurs when substances in solution react to form a solid insoluble salt. This salt is called a precipitate. For example, when a solution of lead(II) nitrate (Pb(NO3)2) is mixed with a solution of potassium iodide (KI), a yellow precipitate forms. This precipitate is lead(II) iodide (PbI2). Since potassium ion and nitrate ion do not take part in the precipitation reaction, they are not shown in the net ionic equation. Ions which do not take part in a reaction are called spectator ions. A solubility table helps in predicting the solubility of a salt. Problem: What is the precipitate when a solution of nickel(II) nitrate (Ni(NO3)2) is mixed with a solution of sodium carbonate (Na2CO3)? First, identify the ions in the solution (Ni2+, NO3–, Na+, and CO32–). Second, check a solubility table for information on these ions. Compounds containing alkali metal ions such as
sodium ion (Na+) tend to be soluble, so sodium ion will not precipitate. Compounds containing nitrate ion (NO3) also tend to be soluble, so nitrate ion will not precipitate.
However, compounds containing carbonate ion (CO3
2–) tend to be insoluble. Therefore, the precipitate is nickel(II) carbonate (NiCO3).