Question

In CH₄ molecule, there are four C – H bounds. If two adjacent bonds are in $\widehat{i} + \widehat{j} + \widehat{k}$and $\widehat{i} - \widehat{j} - \widehat{k}$ direction, then fin d the angle between these bonds.

• A. sin^-1$\left( \frac{- 1}{3} \right)$
• B. cos^-1$\left( \frac{1}{3} \right)$
• C. sin^-1$\left( \frac{1}{3} \right)$
• D. cos^-1$\left( \frac{- 1}{3} \right)$

Answer 1

Answer: (D)

cos^-1$\left( \frac{- 1}{3} \right)$

Answer 2

$\cos\theta = \frac{\left( \widehat{i} + \widehat{j} + \widehat{k} \right)\left( \widehat{i} - \widehat{j} - \widehat{k} \right)}{\sqrt{3}.\sqrt{3}} = \frac{- 1}{3}$

θ = cos^-1$\left( \frac{- 1}{3} \right)$