In a methane `(CH_(4)` molecule each hydrogen atom is at a corner of a regular tetrahedron with the carbon atom at the centre. In coordinates where one of the `C-H` bond in the `hat(i)-hat(j)-hat(k)`, an adjacent `C-H` bond in the `hat(i)-hat(j)-hat(k)` direction. Then angle between these two bonds.

Options

A. `cos^(-1)(2/3)`
B. `cos^(-1)(2/3)`
C. `cos^(-1)(-1/3)`
D. `cos^(-1)(1/3)`

Answer

C

Explanation

`cos theta=((hat(i)+hat(j)+hat(k)).(hat(i)-hat(j)-hat(k)))/(sqrt(3))= (1-1-1)/3= -1/3`