Question

The ratio of number of water molecules in Mohr's salt and potash alum is _________ \(\times 10^{-1}\). (Integer answer)

Hint:

Always remember the formulas: Mohr's salt has 6 waters, and all standard alums have 24 waters in their double salt formula unit (\(M_2SO_4 \cdot M'_2(SO_4)_3 \cdot 24H_2O\)).

Answer 1

Correct Answer: 5

Step 1: Understanding the Concept:
Double salts like Mohr's salt and Potash Alum contain a fixed number of water molecules of crystallization per formula unit.
Step 2: Detailed Explanation:
1. Mohr's Salt: Its chemical formula is \((NH_4)_2Fe(SO_4)_2 \cdot 6H_2O\).
Number of water molecules = 6.
2. Potash Alum: Its chemical formula is \(K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O\).
Number of water molecules = 24.
3. Calculation of Ratio:
\[ \text{Ratio} = \frac{\text{Water in Mohr's Salt}}{\text{Water in Potash Alum}} = \frac{6}{24} = 0.25 \]
Expressing in terms of \(10^{-1}\):
\[ 0.25 = 2.5 \times 10^{-1} \]
Rounding to the nearest integer as per standard JEE practice for this specific question type: 2.
Step 3: Final Answer:
The value is 2.