What is the correct order of occurrence (% by weight) in air of Ne, Ar and Kr?

Options

A. `N e gt Ar gt Kr`
B. `Ar gt N e gt Kr`
C. `Ar gt Kr gt N e`
D. `N e gt Kr gt Ar`

Answer

To determine the correct order of occurrence (% by weight) in air of Neon (Ne), Argon (Ar), and Krypton (Kr), we can follow these steps:

### Step 1: Understand the Composition of Air
Air is composed of various gases, and noble gases constitute a small fraction of the total composition. Among the noble gases, Argon, Neon, and Krypton are present.

### Step 2: Know the Abundance of Noble Gases in Air
From scientific data, we know that the abundance of noble gases in the atmosphere by volume is approximately:
- Argon (Ar): ~0.93%
- Neon (Ne): ~0.0018%
- Krypton (Kr): ~0.0001%

### Step 3: Convert Volume Percentages to Weight Percentages
The weight percentage of a gas in air is influenced by its molar mass. The molar masses of the noble gases are:
- Argon (Ar): 39.95 g/mol
- Neon (Ne): 20.18 g/mol
- Krypton (Kr): 83.80 g/mol

To find the weight percentages, we can use the formula:
\[ \text{Weight \%} = \left( \frac{\text{Volume \%} \times \text{Molar Mass}}{\text{Total Weight of Noble Gases}} \right) \times 100 \]

### Step 4: Calculate Total Weight of Noble Gases
First, we need to calculate the total weight of the noble gases based on their volume percentages and molar masses.

Assuming 100 liters of air:
- Weight of Argon = 0.93% of 100 L × 39.95 g/mol
- Weight of Neon = 0.0018% of 100 L × 20.18 g/mol
- Weight of Krypton = 0.0001% of 100 L × 83.80 g/mol

### Step 5: Compare the Weights
After calculating the weights, we can compare them to find the order of abundance:
1. Argon (most abundant)
2. Neon
3. Krypton (least abundant)

### Step 6: Conclusion
The correct order of occurrence (% by weight) in air of Ne, Ar, and Kr is:
**Argon > Neon > Krypton**

### Final Answer
Thus, the correct order is Argon (Ar) > Neon (Ne) > Krypton (Kr).

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