Question

Normality of \(0.3 \mathrm{M} \mathrm{H}_{3} \mathrm{PO}_{4}\) solution is: (a) \(0.1 \mathrm{~N}\) (b) \(0.45 \mathrm{~N}\) (c) \(0.6 \mathrm{~N}\) (d) \(0.9 \mathrm{~N}\)

Short answer

(d) 0.9 N

Step-by-step solution

Understand Normality and Molarity

Normality (N) is a measure of concentration equivalent to molarity (M) adjusted by the number of hydrogen ions (H⁺) an acid can donate or hydroxide ions (OH⁻) a base can accept. For acids, this depends on the basicity, which is the number of moles of replaceable hydrogen ions. The given acid, phosphoric acid (H₃PO₄), can donate 3 moles of H⁺, so its basicity is 3.

Use the Normality Formula

The formula relating normality (N) to molarity (M) for an acid is: \[ N = M \times ext{Basicity} \]Substitute the given values into the formula:\[ N = 0.3 \text{ M} \times 3 \]

Calculate Normality

Calculate the normality by multiplying the molarity by the basicity:\[ N = 0.3 \times 3 = 0.9 \]}],

Select the Correct Answer

Based on the calculation, the normality of the solution is 0.9 N. Therefore, the correct answer is (d) \(0.9 \mathrm{~N}\).

Key concepts

Molarity

Molarity is a crucial concept in chemistry, particularly when discussing solutions. It allows us to express the concentration of a solute in a solution.
Essentially, molarity (M) is defined as the number of moles of solute per liter of solution. This means if you have 1 mole of a substance dissolved in a total solution volume of 1 liter, the molarity of the solution is 1 mol/L.

• Molarity helps in comparing the concentrations of solute present in different solutions.
• It is expressed in terms of moles per liter (mol/L), commonly referred to as Molar (M).

You can find the molarity using the formula:
\[ M = \frac{n}{V} \]where:

• \( n \) is the number of moles of the solute
• \( V \) is the volume of the solution in liters

For example, in the case of a 0.3 M phosphoric acid solution, it means there are 0.3 moles of phosphoric acid per liter of solution.

Acid-Base Chemistry

Acid-base chemistry is an essential field of study that explores the reactions between acids and bases. Acids are substances that can donate hydrogen ions (H⁺), while bases are substances that can accept hydrogen ions.
In an aqueous solution, acids increase the concentration of H⁺ ions, making the solution acidic, while bases increase hydroxide ions (OH⁻), making the solution basic.

• **pH Scale**: This measures how acidic or basic a solution is. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic solution.
• **Neutralization**: An acid and a base can react to form water and a salt, a process known as neutralization.

Understanding acid-base chemistry is essential for numerous applications, including drug formulation, environmental science, and food chemistry.
In this context, understanding how acids like phosphoric acid behave in water is crucial. Phosphoric acid (H₃PO₄) is a triprotic acid, meaning it can donate up to three hydrogen ions, making it an excellent example for calculating normality.

Phosphoric Acid

Phosphoric acid is a triprotic acid, often represented by the chemical formula \( \text{H}_3\text{PO}_4 \). This means that in solution, it can donate up to three hydrogen ions (H⁺). This gives phosphoric acid a unique property of having a basicity of 3.
Using phosphoric acid in laboratories and industry highlights its versatility:

• **As an Acid**: It can participate in reactions where donating hydrogen ions is essential.
• **Applications**: Commonly used in fertilizers, food additives, and even as a rust remover due to its corrosive nature.
• **Role in Calculations**: Because phosphoric acid can provide three hydrogen ions, it's pivotal in computing properties like normality. For instance, if a solution has a molarity of 0.3 M, the normality becomes 0.9 N due to multiplying the molarity by its basicity.

Phosphoric acid's role in chemistry extends beyond simple calculations, influencing many industrial and chemical processes due to its acidifying strength and ability to act as a reactant in various reactions.