Understanding Neutrons in a Mole of Heavy Water

Heavy Water (Deuterium Oxide): Chemical Composition and Isotopic Makeup

Heavy water, also known chemically as deuterium oxide (D2O), is a unique form of water composed of two deuterium atoms and one oxygen atom. Deuterium (D), an isotope of hydrogen, has one proton and one neutron in its nucleus, whereas oxygen (O) has eight protons and can vary in the number of neutrons. In the context of heavy water, we often deal with the isotope 16O, which has eight neutrons.

Neutrons in Heavy Water Molecules

To understand the total number of neutrons in a mole of heavy water (D2O), we need to break down the contributions from both deuterium and oxygen atoms.

Neutrons from Deuterium

Each deuterium atom has one neutron in its nucleus. Therefore, in each 2H2O molecule, there are two neutrons (one from each deuterium atom).

The formal mathematical representation of this is:

1 neutron/De2H 2 neutrons per molecule.

Neutrons from Oxygen

One mole of oxygen has 8 neutrons, as it typically consists of the 16O isotope, which has eight neutrons. However, in the context of heavy water, we consider one mole of 16O.

Total Neutrons in One Mole of Heavy Water

Combining these contributions, we can calculate the total number of neutrons in one mole of heavy water. Let's break it down step by step:

Each D2O molecule contains two neutrons from deuterium. One mole of deuterium (D) equals one mole of 2H, which contains two moles of deuterium atoms. Therefore, one mole of D2O contains two moles of neutrons from deuterium. One mole of oxygen (O) contains eight neutrons from 16O.

Thus, the total number of neutrons in one mole of heavy water (D2O) is:

2 neutrons from deuterium 8 neutrons from oxygen 10 neutrons per molecule.

The Calculation in Depth

Let's perform the calculation step by step for clarity:

Neutrons from deuterium: In a molecule of D2O, there are 2 D atoms, and each D atom has 1 neutron. Therefore, each D2O molecule contains 2 neutrons from deuterium.

One mole of heavy water (D2O) contains 6.023 x 1023 molecules. Thus, one mole of D2O contains:

2 neutrons/molecule x 6.023 x 1023 molecules 1.2046 x 1024 neutrons from deuterium.

Neutrons from oxygen: One mole of oxygen (O) contains 8 neutrons from 16O. Hence, one mole of D2O (since it contains one O atom per molecule) contains 8 neutrons from oxygen.

Thus, the total number of neutrons in one mole of heavy water (D2O) is:

1.2046 x 1024 neutrons (from deuterium) 8 x 6.023 x 1023 neutrons (from oxygen) 1.2046 x 1024 4.8184 x 1024 neutrons 6.022 x 1024 neutrons.

Conclusion

The total number of neutrons in one mole of heavy water (D2O) is 10. This includes 2 neutrons from each of the deuterium atoms (an isotope of hydrogen) and 8 neutrons from the 16O isotope of oxygen.

Therefore, the answer is 10 neutrons per mole of heavy water, as each D2O molecule contributes 10 neutrons (2 from deuterium and 8 from oxygen).