What is the standard for the molecular weights of molecules ?

Answer

To determine the standard for the molecular weights of molecules, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Molecular Weight (MW)**:
- Molecular weight is often abbreviated as MW. It represents the mass of a molecule in atomic mass units (AMU).

2. **Units of Molecular Weight**:
- Molecular weight is expressed in Atomic Mass Units (AMU) or Daltons (Da). Both terms are used interchangeably in chemistry.

3. **Definition of 1 AMU**:
- 1 AMU is defined as one-twelfth (1/12) of the mass of a carbon-12 atom. This means that the carbon-12 isotope serves as a standard reference for measuring atomic and molecular weights.

4. **Standard for Molecular Weight**:
- The standard for molecular weight is based on the carbon-12 isotope. Therefore, when calculating the molecular weight of other molecules, they are compared to the mass of carbon-12.

5. **Conclusion**:
- The standard for molecular weights of molecules is the carbon-12 isotope (C-12).

### Final Answer:
The standard for the molecular weights of molecules is based on the carbon-12 isotope (C-12).

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