Question

Dihydrogen reacts with dioxygen $O_2$ to form water. Write the name and formula of the product when the isotope of hydrogen which has one proton and one neutron in its nucleus is treated with oxygen. Will the reactivity of both the isotopes be the same towards oxygen? Justify your answer.

Answer 1

1.$2H_2+O_2⟶2H_{2}O$

$2H_2$=Dihydrogen

$O_2$=oxygen

$2H_{2}O$=water

i.) There are $2$ types of isotopes of hydrogen they are

a. Deuterium (D)

b. Tritium (T)

Where Deuterium has $1$ proton, $1$ electron and $1$ neutron, while Tritium has $1$ proton, $1$ electron and $2$ neutron

Both are radioactive isotope of Hydrogen;

From which Deuterium is most stable among hydrogen and tritium.

2. When Deuterium is treated with oxygen it forms deuterium oxide, i.e.,

$2D_2+O_2⟶D_{2}O$

$2D_2$=Deuterium

$O_2$=oxygen

$D_{2}O$=Deuterium oxide

The product formed is Deuterium oxide with chemical formula $\left(D_{2}O\right)$

$D_{2}O$ is a stable product and will not get dissociated easily likewise in $H_{2}O$

Reactivity depends on no. of the electrons present and on the bond length.

Shorter the bond length lesser the reactivity and vice versa

The bond length in $H_{2}O$ is bigger than the $D_{2}O$

Therefore the $H^{+}$ released from $H_{2}O$ is more acidic than $D^{+}$ from $D_{2}O$

The release of $H^{+}$ does not require much energy while removal of $D^{+}$ will require high energy

Hyperconjugation is seen (refer Image) bond; and heterolytic fission is $H_{2}O$

While $D_{2}O$ forms free radical and not ions in normal condition.

Therefore the $D_{2}O$ is also called as heavy water

$D_{2}O$ being more stable than $H_2$ so it will not react as fast as $H_2$.

$H_2$ in presence of sunlight will go to undergo homolytic fission;

So the formation of H takes place easily while

$D_2$ will not undergo fission easily.