Chapter 9, Problem 112A

Precipitate Formation ne addition of hydrochloric acid to beakers containing solutions of either sodium chloride $\text{(NaCl)}$ or silver nitrate ${\text{(KNO}}_{\text{3}}\text{)}$ causes a whiteprecipitate in one of the beakers.

a. Which beaker contains a precipitate?
b. What is the precipitate?
c. Write a chemical equation showing the reaction.
d. Classify the reaction.

Interpretation Introduction

(a)

Interpretation:

The beaker containing a precipitate needs to be determined.

Concept introduction:

The reactivity series of metals is as follows:

Lithium > Rubidium > Potassium > Calcium > Sodium > Magnesium > Aluminium > Manganese > Zinc > Iron > Nickel > Tin > Lead > Copper > Silver > Platinum > Gold

The metal higher on the series is the most active and will not be precipitated. The metal lower on the series is less active and hence will be precipitated.

Answer to Problem 112A

The beaker containing a mixture of $\text{HCl}$ and ${\text{AgNO}}_{\text{3}}$ will contain a precipitate.

Explanation of Solution

Both HCl and NaCl are water soluble compounds. Because of this, adding HCl to NaCl will generate no precipitate. Hence, no products will be formed.

But addition of HCl to ${\text{AgNO}}_{\text{3}}$ will generate a precipitate. It is because the product $\text{AgCl}$ is not soluble in water, i.e. it is water insoluble.

So, the beaker containing a mixture of $\text{HCl}$ and ${\text{AgNO}}_{\text{3}}$ will generate a precipitate.

Interpretation Introduction

Interpretation:

A precipitate needs to be determined.

Concept introduction:

The reactivity series of metals is as follows:

Lithium > Rubidium > Potassium > Calcium > Sodium > Magnesium > Aluminium > Manganese > Zinc > Iron > Nickel > Tin > Lead > Copper > Silver > Platinum > Gold

The metal higher on the series is the most active and will not be precipitated. The metal lower on the series is less active and hence will be precipitated.

Answer to Problem 112A

The precipitate on adding HCl to ${\text{AgNO}}_{\text{3}}$ is $\text{AgCl}$.

Explanation of Solution

Addition of HCl to ${\text{AgNO}}_{\text{3}}$ will generate a precipitate. It is because the product is not soluble in water, i.e. it is water insoluble. The product formed is $\text{AgCl}$.

Interpretation Introduction

Interpretation:

A chemical equation showing the reaction and formation of precipitate needs to be determined.

Concept introduction:

In a chemical reaction, the reactants are written on the left side of the equation and the product is written on the right side. The product and the reactants contain an arrow between them showing the proceeding of the reaction from the reactants to the products.

A chemical equation is balanced by balancing the number of moles of each element on the reactants and on the products according to the law of conservation of matter.

Answer to Problem 112A

The chemical equation of the reaction is,

$\text{HCl}\left(\text{aq}\right)\text{+}{\text{AgNO}}_{\text{3}}\left(\text{aq}\right)\to \text{AgCl}\left(\text{s}\right){\text{+HNO}}_{\text{3}}\left(\text{aq}\right)$

Explanation of Solution

Addition of HCl to ${\text{AgNO}}_{\text{3}}$ will generate a precipitate of $\text{AgCl}$.

The chemical equation can be given as,

$\text{HCl}\left(\text{aq}\right)\text{+}{\text{AgNO}}_{\text{3}}\left(\text{aq}\right)\to \text{AgCl}\left(\text{s}\right){\text{+HNO}}_{\text{3}}\left(\text{aq}\right)$

Interpretation Introduction

Interpretation:

The type of the reaction needs to be determined.

Concept introduction:

In a chemical reaction, the reactants are written on the left side of the equation and the product is written on the right side. The product and the reactants contain an arrow between them showing the proceeding of the reaction from the reactants to the products.

A chemical equation is balanced by balancing the number of moles of each element on the reactants and on the products according to the law of conservation of matter.

Chemical reactions are classified according to the products they form as synthesis reaction, replacement reaction, oxidation reaction, combustion reaction, double-replacement reaction etc.

Answer to Problem 112A

The reaction,

$\text{HCl}\left(\text{aq}\right)\text{+}{\text{AgNO}}_{\text{3}}\left(\text{aq}\right)\to \text{AgCl}\left(\text{s}\right){\text{+HNO}}_{\text{3}}\left(\text{aq}\right)$ is a double displacement type reaction.

Explanation of Solution

The reaction,

$\text{HCl}\left(\text{aq}\right)\text{+}{\text{AgNO}}_{\text{3}}\left(\text{aq}\right)\to \text{AgCl}\left(\text{s}\right){\text{+HNO}}_{\text{3}}\left(\text{aq}\right)$ is a double displacement type reaction. It is because, the two compounds $\text{HCl}$ and ${\text{AgNO}}_{\text{3}}$ swap their anions.