Question

Assuming all the four valencies of carbon atom in propane pointing towards the corners of a regular tetrahedron; the distance (in $\dot{A}$) between the terminal carbon atoms in propane will be: (write the value of the nearest integer)
Given: $C-C$ single bond length is $1.54$ $\dot{A}$.

Answer 1

Since each $C$ atom has tetrahedral geometry, the $C-C$ bond angle will be ${109.5}^o$

$\theta =\frac{180-109.5}{2}={35.25}^o$
The distance between terminal carbon atoms $=2cos\theta \times$ C-C single bond length

It will be $2cos35.25\times 1.54=2\times 0.82\times 1.54=2.514A^o$