What is called chemical equivalent?
2 Answers
The **chemical equivalent** (also called the equivalent weight or equivalent mass) of a substance refers to the mass of that substance which will react with or supply a fixed amount of another substance, typically hydrogen ions (H⁺) or electrons, in a chemical reaction.
In more specific terms, it is the amount of a substance that can:
- Combine with or displace **1 mole of hydrogen ions (H⁺)** in an acid-base reaction, or
- Donate or accept **1 mole of electrons** in a redox (oxidation-reduction) reaction.
### How to Calculate Chemical Equivalent:
The chemical equivalent (E) is generally calculated using the formula:
\[
E = \frac{M}{n}
\]
where:
- \(E\) = Equivalent weight
- \(M\) = Molar mass of the substance (in grams per mole)
- \(n\) = Number of electrons lost or gained in a redox reaction, or the number of H⁺ ions replaced or supplied in an acid-base reaction.
The value of \(n\) will depend on the type of reaction:
1. **For acids or bases**: It is the number of H⁺ ions the substance can donate (in the case of an acid) or accept (in the case of a base). For example:
- In **HCl (Hydrochloric acid)**, 1 mole of HCl donates 1 mole of H⁺ ions, so the equivalent weight is the molar mass of HCl.
- In **H₂SO₄ (Sulfuric acid)**, 1 mole of H₂SO₄ donates 2 moles of H⁺ ions, so its equivalent weight is half its molar mass.
2. **For redox reactions**: \(n\) is the number of electrons transferred per mole of the substance. For example:
- In **Fe²⁺ to Fe³⁺** conversion (oxidation), 1 electron is involved, so the equivalent weight of iron in this reaction would be its molar mass divided by 1.
### Examples of Chemical Equivalent:
1. **Sodium Hydroxide (NaOH)** in a reaction with an acid:
- Molar mass of NaOH = 40 g/mol
- It releases 1 mole of hydroxide ions (OH⁻) per mole, which neutralizes 1 mole of H⁺ ions.
- So, the equivalent weight of NaOH = 40 g.
2. **Sulfuric Acid (H₂SO₄)** in an acid-base reaction:
- Molar mass of H₂SO₄ = 98 g/mol
- Each molecule of H₂SO₄ can donate 2 moles of H⁺ ions, so the equivalent weight of H₂SO₄ = 98/2 = 49 g.
3. **Iron (Fe) in a redox reaction**:
- If Fe²⁺ gets oxidized to Fe³⁺, one electron is lost per Fe²⁺ ion.
- Molar mass of Fe = 56 g/mol
- So, the equivalent weight of iron for this reaction is 56/1 = 56 g.
### Importance of Chemical Equivalent:
- **Stoichiometry**: It simplifies chemical reaction calculations by allowing you to relate different substances in terms of equivalents rather than moles.
- **Titration**: In acid-base titrations, equivalent weight helps calculate how much acid will neutralize a base (and vice versa).
- **Redox reactions**: In redox processes, equivalent weight allows us to balance reactions based on the transfer of electrons.
In summary, the chemical equivalent is a way to measure and compare different substances in reactions by the quantity needed to either donate or accept a fixed number of particles (like electrons or protons).
In more specific terms, it is the amount of a substance that can:
- Combine with or displace **1 mole of hydrogen ions (H⁺)** in an acid-base reaction, or
- Donate or accept **1 mole of electrons** in a redox (oxidation-reduction) reaction.
### How to Calculate Chemical Equivalent:
The chemical equivalent (E) is generally calculated using the formula:
\[
E = \frac{M}{n}
\]
where:
- \(E\) = Equivalent weight
- \(M\) = Molar mass of the substance (in grams per mole)
- \(n\) = Number of electrons lost or gained in a redox reaction, or the number of H⁺ ions replaced or supplied in an acid-base reaction.
The value of \(n\) will depend on the type of reaction:
1. **For acids or bases**: It is the number of H⁺ ions the substance can donate (in the case of an acid) or accept (in the case of a base). For example:
- In **HCl (Hydrochloric acid)**, 1 mole of HCl donates 1 mole of H⁺ ions, so the equivalent weight is the molar mass of HCl.
- In **H₂SO₄ (Sulfuric acid)**, 1 mole of H₂SO₄ donates 2 moles of H⁺ ions, so its equivalent weight is half its molar mass.
2. **For redox reactions**: \(n\) is the number of electrons transferred per mole of the substance. For example:
- In **Fe²⁺ to Fe³⁺** conversion (oxidation), 1 electron is involved, so the equivalent weight of iron in this reaction would be its molar mass divided by 1.
### Examples of Chemical Equivalent:
1. **Sodium Hydroxide (NaOH)** in a reaction with an acid:
- Molar mass of NaOH = 40 g/mol
- It releases 1 mole of hydroxide ions (OH⁻) per mole, which neutralizes 1 mole of H⁺ ions.
- So, the equivalent weight of NaOH = 40 g.
2. **Sulfuric Acid (H₂SO₄)** in an acid-base reaction:
- Molar mass of H₂SO₄ = 98 g/mol
- Each molecule of H₂SO₄ can donate 2 moles of H⁺ ions, so the equivalent weight of H₂SO₄ = 98/2 = 49 g.
3. **Iron (Fe) in a redox reaction**:
- If Fe²⁺ gets oxidized to Fe³⁺, one electron is lost per Fe²⁺ ion.
- Molar mass of Fe = 56 g/mol
- So, the equivalent weight of iron for this reaction is 56/1 = 56 g.
### Importance of Chemical Equivalent:
- **Stoichiometry**: It simplifies chemical reaction calculations by allowing you to relate different substances in terms of equivalents rather than moles.
- **Titration**: In acid-base titrations, equivalent weight helps calculate how much acid will neutralize a base (and vice versa).
- **Redox reactions**: In redox processes, equivalent weight allows us to balance reactions based on the transfer of electrons.
In summary, the chemical equivalent is a way to measure and compare different substances in reactions by the quantity needed to either donate or accept a fixed number of particles (like electrons or protons).
The term "chemical equivalent" is used in chemistry to refer to the amount of a substance that will react with or replace one mole of hydrogen ions (H⁺) or one mole of electrons in a chemical reaction. It is a concept that helps in understanding and calculating the stoichiometry of reactions.
### Key Points:
1. **Definition**:
- The chemical equivalent of a substance is the quantity of that substance that will combine with or displace a fixed amount of another substance in a chemical reaction. This fixed amount is typically one mole of hydrogen ions (H⁺) or one mole of electrons.
2. **Calculation**:
- For acids, the chemical equivalent is the amount of acid that will donate one mole of hydrogen ions (H⁺).
- For bases, it is the amount of base that will react with one mole of hydrogen ions (H⁺).
- For oxidizing and reducing agents, it is the amount of the agent that will accept or donate one mole of electrons.
The chemical equivalent can be calculated using the formula:
\[
\text{Chemical Equivalent} = \frac{\text{Molar Mass}}{\text{N}}
\]
where \( \text{Molar Mass} \) is the mass of one mole of the substance, and \( \text{N} \) is the number of hydrogen ions or electrons the substance can donate or accept.
3. **Applications**:
- **Titration**: In titration, chemical equivalents are used to determine the concentration of a solution by reacting it with a solution of known concentration.
- **Stoichiometry**: It helps in balancing chemical equations and calculating the amounts of reactants and products involved in a reaction.
4. **Examples**:
- For sulfuric acid (H₂SO₄), which can donate 2 moles of hydrogen ions (H⁺), its chemical equivalent is its molar mass divided by 2.
- For sodium hydroxide (NaOH), which can react with one mole of hydrogen ions (H⁺), its chemical equivalent is the same as its molar mass.
Understanding chemical equivalents is essential for accurately performing and interpreting chemical reactions and processes.
### Key Points:
1. **Definition**:
- The chemical equivalent of a substance is the quantity of that substance that will combine with or displace a fixed amount of another substance in a chemical reaction. This fixed amount is typically one mole of hydrogen ions (H⁺) or one mole of electrons.
2. **Calculation**:
- For acids, the chemical equivalent is the amount of acid that will donate one mole of hydrogen ions (H⁺).
- For bases, it is the amount of base that will react with one mole of hydrogen ions (H⁺).
- For oxidizing and reducing agents, it is the amount of the agent that will accept or donate one mole of electrons.
The chemical equivalent can be calculated using the formula:
\[
\text{Chemical Equivalent} = \frac{\text{Molar Mass}}{\text{N}}
\]
where \( \text{Molar Mass} \) is the mass of one mole of the substance, and \( \text{N} \) is the number of hydrogen ions or electrons the substance can donate or accept.
3. **Applications**:
- **Titration**: In titration, chemical equivalents are used to determine the concentration of a solution by reacting it with a solution of known concentration.
- **Stoichiometry**: It helps in balancing chemical equations and calculating the amounts of reactants and products involved in a reaction.
4. **Examples**:
- For sulfuric acid (H₂SO₄), which can donate 2 moles of hydrogen ions (H⁺), its chemical equivalent is its molar mass divided by 2.
- For sodium hydroxide (NaOH), which can react with one mole of hydrogen ions (H⁺), its chemical equivalent is the same as its molar mass.
Understanding chemical equivalents is essential for accurately performing and interpreting chemical reactions and processes.