Heavy water is

Options

A. sea water (`H_(2)O+`salt)
B. `D_(2)O`
C. `H_(2)O_(2)`
D. `H_(2)O` water + Ca and Mg carbonates

Explanation

**Step-by-Step Solution:**

1. **Understanding Heavy Water**: Heavy water is a form of water that contains a heavier isotope of hydrogen known as deuterium. The chemical formula for heavy water is D2O.

2. **Identifying Deuterium**: Deuterium is an isotope of hydrogen. While regular hydrogen (H) has one proton and no neutrons, deuterium (D) has one proton and one neutron. This additional neutron increases the mass of deuterium compared to regular hydrogen.

3. **Comparing Water Forms**: Regular water is composed of two hydrogen atoms and one oxygen atom, represented as H2O. In heavy water, both hydrogen atoms are replaced by deuterium, resulting in the formula D2O.

4. **Mass Comparison**: Since deuterium has a greater mass than regular hydrogen, the overall mass of heavy water (D2O) is greater than that of regular water (H2O). This is why it is termed "heavy" water.

5. **Hydrogen Bonding**: Heavy water (D2O) forms stronger hydrogen bonds compared to regular water due to the presence of deuterium. The bond between deuterium and oxygen is stronger than that between hydrogen and oxygen, making it more difficult to break these bonds.

6. **Conclusion**: Therefore, heavy water is defined as D2O, which is the correct answer to the question.

**Final Answer**: Heavy water is D2O (deuterium oxide).

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