Which one of the following is the lightest?

Options

A. 0.2 mole of hydrogen gas
B. `6.023 xx 10^(22)` molecules of nitrogen
C. 0.1 g of silver
D. 0.1 mole of oxygen gas

Explanation

To determine which of the given options is the lightest, we will calculate the mass of each substance based on the information provided in the question.

### Step-by-Step Solution

**Step 1: Calculate the mass of Hydrogen gas (Option A)**
- We are given 0.2 moles of Hydrogen gas (H₂).
- The molecular weight of Hydrogen gas (H₂) is 2 grams/mole.
- Therefore, the mass of 0.2 moles of Hydrogen gas is calculated as:
\[ \text{Mass of H₂} = \text{Number of moles} \times \text{Molecular weight} = 0.2 \, \text{moles} \times 2 \, \text{g/mole} = 0.4 \, \text{grams} \]

**Step 2: Calculate the mass of Nitrogen gas (Option B)**
- We are given 1 mole of Nitrogen gas (N₂).
- The molecular weight of Nitrogen gas (N₂) is 28 grams/mole.
- Therefore, the mass of 1 mole of Nitrogen gas is:
\[ \text{Mass of N₂} = 1 \, \text{mole} \times 28 \, \text{g/mole} = 28 \, \text{grams} \]

**Step 3: Calculate the mass of Silver (Option C)**
- We are given 0.1 grams of Silver (Ag).
- Therefore, the mass of Silver is simply:
\[ \text{Mass of Ag} = 0.1 \, \text{grams} \]

**Step 4: Calculate the mass of Oxygen gas (Option D)**
- We are given 0.1 moles of Oxygen gas (O₂).
- The molecular weight of Oxygen gas (O₂) is 32 grams/mole.
- Therefore, the mass of 0.1 moles of Oxygen gas is:
\[ \text{Mass of O₂} = 0.1 \, \text{moles} \times 32 \, \text{g/mole} = 3.2 \, \text{grams} \]

**Step 5: Compare the masses**
- Mass of Hydrogen (H₂) = 0.4 grams
- Mass of Nitrogen (N₂) = 28 grams
- Mass of Silver (Ag) = 0.1 grams
- Mass of Oxygen (O₂) = 3.2 grams

**Conclusion:**
The lightest substance among the options is **Silver (0.1 grams)**.