How to find equivalent weight of molecule given from the equation can u give some more examples ?

For example if it is asked to find equivalent weight of HNO₃ in the reaction HNO₃+H₂S----->H₂O+NO+S?

To determine the equivalent weight of a molecule, we first need to understand what equivalent weight means. It is defined as the mass of a substance that will combine with or displace one mole of hydrogen atoms or one mole of electrons in a chemical reaction. The equivalent weight can be calculated using the formula:

Formula for Equivalent Weight

The equivalent weight (EW) can be calculated using the following equation:

EW = Molar Mass / n

Here, Molar Mass is the molecular weight of the compound, and n is the number of moles of reactive species (like H+ ions or electrons) that one mole of the substance can provide or react with in the given reaction.

Step-by-Step Example: Finding the Equivalent Weight of HNO3

Let's break down the example you provided: the reaction of nitric acid (HNO3) with hydrogen sulfide (H2S) to produce water (H2O), nitrogen monoxide (NO), and sulfur (S).

1. Identify the Reaction

The balanced reaction is:

HNO3 + H2S → H2O + NO + S

2. Determine the Change in Oxidation States

In this reaction, we need to analyze the oxidation states of the elements involved:

• N in HNO3 goes from +5 in HNO3 to +2 in NO.
• S in H2S goes from -2 in H2S to 0 in S.

Here, nitrogen is reduced (gaining electrons), and sulfur is oxidized (losing electrons).

3. Calculate the Number of Electrons Transferred

For each mole of HNO3, it reduces by 3 electrons (from +5 to +2), and for each mole of H2S, it oxidizes by 2 electrons (from -2 to 0). Therefore, in this reaction:

n = 3 (for HNO3)

4. Find the Molar Mass of HNO3

The molar mass of HNO3 is calculated as follows:

• H: 1 g/mol
• N: 14 g/mol
• O: 16 g/mol × 3 = 48 g/mol

So, the total molar mass of HNO3 is:

1 + 14 + 48 = 63 g/mol

5. Calculate the Equivalent Weight

Now, we can use the formula for equivalent weight:

EW = Molar Mass / n

Substituting the values we found:

EW = 63 g/mol / 3 = 21 g/equiv

Additional Example: Finding the Equivalent Weight of H2SO4

Let's consider another example with sulfuric acid (H2SO4) in a reaction where it donates two protons:

H2SO4 + 2 NaOH → Na2SO4 + 2 H2O

1. Identify the Molar Mass of H2SO4

• H: 1 g/mol × 2 = 2 g/mol
• S: 32 g/mol
• O: 16 g/mol × 4 = 64 g/mol

Total molar mass = 2 + 32 + 64 = 98 g/mol

2. Determine the Number of Protons Donated

In this case, sulfuric acid donates 2 protons, so n = 2.

3. Calculate the Equivalent Weight

Using the equivalent weight formula:

EW = 98 g/mol / 2 = 49 g/equiv

By following these steps, you can find the equivalent weight of various substances in different reactions. Understanding the concept of oxidation states and the number of electrons transferred is crucial in determining the equivalent weight accurately.