1.7gm of ammonium salt was heated with excess of NaOH . The ammonia released in the process neutralises 100 c.c. solution of N/5 H2SO4 . What is the percentage of ammonia in the salt

To determine the percentage of ammonia in the ammonium salt, we need to follow a series of logical steps involving stoichiometry and the properties of acids and bases. Let's break this down step by step.

Understanding the Reaction

When ammonium salt is heated with sodium hydroxide (NaOH), ammonia gas (NH3) is released. The reaction can be represented as:

• NH4Cl + NaOH → NH3 + NaCl + H2O

In this case, we are given that the ammonia produced neutralizes a specific volume of sulfuric acid (H2SO4). The concentration of the sulfuric acid solution is N/5, which means it is a 0.2 N solution (since N/5 is equivalent to 0.2 N).

Calculating Moles of H2SO4

First, we need to calculate the number of moles of sulfuric acid in the 100 c.c. solution. The normality (N) of H2SO4 is 0.2 N, and since normality is defined as equivalents per liter, we can find the moles:

• Volume of H2SO4 = 100 c.c. = 0.1 L
• Moles of H2SO4 = Normality × Volume = 0.2 × 0.1 = 0.02 moles

Neutralization Reaction

In the neutralization reaction between ammonia and sulfuric acid, the balanced equation is:

• 2 NH3 + H2SO4 → (NH4)2SO4

This indicates that 2 moles of ammonia react with 1 mole of sulfuric acid. Therefore, the moles of ammonia produced can be calculated as follows:

• Moles of NH3 = 2 × Moles of H2SO4 = 2 × 0.02 = 0.04 moles

Finding Mass of Ammonia

Next, we need to convert the moles of ammonia into grams. The molar mass of ammonia (NH3) is approximately 17 g/mol. Thus, the mass of ammonia can be calculated as:

• Mass of NH3 = Moles × Molar Mass = 0.04 × 17 = 0.68 g

Calculating the Percentage of Ammonia in the Salt

Now that we have the mass of ammonia released, we can find the percentage of ammonia in the original ammonium salt. The mass of the ammonium salt used was 1.7 g. The percentage can be calculated using the formula:

• Percentage of NH3 = (Mass of NH3 / Mass of Ammonium Salt) × 100

Substituting the values we have:

• Percentage of NH3 = (0.68 g / 1.7 g) × 100 ≈ 40%

Final Thoughts

Thus, the percentage of ammonia in the ammonium salt is approximately 40%. This calculation illustrates the relationship between the amount of ammonia produced and the original mass of the salt, showcasing the principles of stoichiometry and acid-base reactions.