Question

How do you balance a double replacement reaction using the solubility chart? and How do you read the solubility chart?

Answer 1

Double displacement reaction or salt metathesis reaction:

Definition: Double displacement reaction is a chemical reaction between two compounds where the positive ions in compounds mutually exchanged between them. For example

AgNO3 HCl HNO3+ AgCl J

Ag⁺ is replaced by H⁺ and AgCl is precipitated.

What is solubility chart ?

Solubility chart is a table containing a column of cation and a row of anions where cations are listed across the top and anions are listed vertically.

Solubility chart predicts the solubility, sparingly solubility or insolubility of the the resulting compound.

To predict the solubility, find the cell where column containing cation and row containing anion meet and find the prediction about the solubility of resulting compound.

Balancing a double displacement reaction:

For example, lets discuss the reaction between Na₂S and HCl

Na2SHCl?

Step one: Identification of ionic species with their charge

АхBy Вy | Аx- Ах -Ву ХАY+ YBX Cation Anion

In Na₂S, there are 2Na⁺ (Cation) and 1 S^2- (Anion)

In HCl, there are 1 H⁺ (cation) and 1 Cl^- (Anion)

Step 2: Replace the cations of the reaction

Replace the Na⁺ with H⁺

Na2S HClHS + NaCl

Notice that the cation partners are changed with anions.

Step 3: Balance the displacement reaction [Number according to charge]

Na2S HClHS + NaCl

In this reaction number of ions are not balanced.

(Ions) Na S H Cl H S Na Cl

(Numbers) 2 1 1 1 1 1 1 1

We can balance the reaction by adding coefficients as per requirement

There are 2 Na⁺ on left side, then multiply NaCl with 2 on right side.

Na2S HClHS +2NaC]

Now there becomes 2 Cl^- on right side, lets multiply HCl by 2 on left side.

Na2S 2HC HS+2NaC]

Now there are balanced number of S^2- on both side, but there are 2H⁺ on left side, lets balance the number of H⁺ on the right side-

H2S+ 2NaCl Na2S 2HC

That's the finally balanced equation of double displacement reaction.