The molecular mass of water `(H_2O)` is-

Options

A. 12g/mol
B. 18g/mol
C. 20g/mol
D. 15g/mol

Answer

To find the molecular mass of water (H₂O), we need to follow these steps:

### Step 1: Identify the elements in the compound
Water (H₂O) consists of two elements: hydrogen (H) and oxygen (O).

### Step 2: Determine the number of atoms of each element
In one molecule of water:
- There are 2 hydrogen atoms.
- There is 1 oxygen atom.

### Step 3: Find the atomic mass of each element
The atomic masses of the elements are approximately:
- Hydrogen (H) = 1 gram/mole
- Oxygen (O) = 16 grams/mole

### Step 4: Calculate the total mass contributed by each element
- For hydrogen:
\[ \text{Mass from hydrogen} = \text{Number of H atoms} \times \text{Atomic mass of H} = 2 \times 1 = 2 \text{ grams/mole} \]

- For oxygen:
\[ \text{Mass from oxygen} = \text{Number of O atoms} \times \text{Atomic mass of O} = 1 \times 16 = 16 \text{ grams/mole} \]

### Step 5: Sum the total mass to find the molecular mass of water
\[ \text{Molecular mass of water (H₂O)} = \text{Mass from hydrogen} + \text{Mass from oxygen} = 2 + 16 = 18 \text{ grams/mole} \]

### Final Answer
The molecular mass of water (H₂O) is **18 grams/mole**.

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