Mole Concept And Molar Masses

To determine in which case the number of water molecules is maximum, we need to calculate the number of moles of water present in each option, because the number of molecules is directly proportional to the number of moles.

1. Understanding the relevant concept: The number of molecules can be calculated using Avogadro's number, which is molecules per mole. Hence, more moles mean more molecules.
2. Option 1: 18 mL of water
   • The density of water is . Therefore, 18 mL of water has a mass of 18 g.
   • Molecular weight of water (H₂O) = 18 g/mol.
   • Number of moles of water = .
   • Number of molecules = .
3. Option 2: 0.00224 L of water vapours at 1 atm and 273 K
   • At STP (Standard Temperature and Pressure), 1 mole of any gas occupies 22.4 L.
   • Moles of water vapor = .
   • Number of molecules = .
4. Option 3: 0.18 g of water
   • Molecular weight of water = 18 g/mol.
   • Number of moles = .
   • Number of molecules = .
5. Option 4: mol of water
   • Number of molecules = .
6. Conclusion: The option with the maximum number of molecules is determined by the calculation results. Option 1 gives the largest number of molecules.

Hence, the number of molecules of water is maximum in 18 mL of water.

To solve this problem, we need to consider the chemical reaction involved in the production of ammonia through the Haber process. The balanced chemical equation for this reaction is:

N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)

This equation tells us that 1 mole of nitrogen gas reacts with 3 moles of hydrogen gas to produce 2 moles of ammonia. Thus, the stoichiometric ratio between hydrogen and ammonia is 3:2.

Given in the problem, we need to produce 20 moles of ammonia. Let's calculate the number of moles of hydrogen required:

According to the stoichiometric ratio, 2 moles of ammonia require 3 moles of hydrogen. Therefore, to find out how many moles of hydrogen are needed for 20 moles of ammonia, we set up the proportion:

\frac{3 \text{ moles of } H_2}{2 \text{ moles of } NH_3} = \frac{x \text{ moles of } H_2}{20 \text{ moles of } NH_3}

Cross-multiplying gives us:

2x = 20 \times 3

2x = 60

Dividing each side by 2 to solve for x gives:

x = \frac{60}{2} = 30

Therefore, 30 moles of hydrogen gas are required to produce 20 moles of ammonia.

Hence, the correct answer is 30.