Which equation must be used to determine the mass of solid formed in a precipitation reaction?

Question

1. Balanced ionic equation

 

2. Balanced net ionic equation

 

3. Balanced molecular equation

 

4. Two of the above can be used 

 

5. All of the above can be used

 

I predict it's all of the above. 

Answer 1

As long as the chemical equation is correctly BALANCED, it can be used to determine the mass of a precipitate.  So, the answer would be (5) all of the above.  

 

Note:  It is true that the net ionic equation must be used to determine if a reaction takes place at all, but once that is known, any of the balanced equations can be used to obtain mole ratios and hence, mass of precipitate.

Answer 2

Hello Kacy

 

The answer is 2) Balanced net ionic equation.

 

In an ionic equation, there are spectator ions present that do not participate in the precipitation reaction and must be cancelled when writing the overall chemical reaction.  An example is the reaction of silver nitrate with sodium chloride to form insoluble silver chloride.

 

Molecular Equation

 

AgNO₃ (aq) + NaCl (aq) → NaNO₃ (aq) + AgCl (s)

 

Ionic equation:  All substances that are "aq" in the molecular equation must be written in ionic form.

 

Ag⁺ (aq) + NO₃^- (aq) + Na⁺ (aq) + Cl^- (aq) → Na⁺ (aq) + NO₃^- (aq) + AgCl (s)

 

In the ionic equation, you can see that Na⁺ and NO₃^- are present on both sides of the equation, therefore, they are the spectator ions and must be cancelled as they do not participate in the precipitation of AgCl.

 

Net Ionic Equation

 

Ag⁺ (aq) + Cl^- (aq) →  AgCl (s) 

Answer 3

It's not a molecular equation, it's an ionic equation.  So, maybe two of the above.