Answer to Question #197476 in Organic Chemistry for Earl

Question

Which of the following statements is INCORRECT? (1) H-C≡N is a linear molecule and the bond angle of H-C-N is 180 O (2) Formaldehyde is a trigonal planar molecule with the H-C-H bond angle of 120 O (3) Water is a bent molecule. The H-O-H bond angle is 120 O and the arrangement of the electron pairs on the oxygen atom is tetrahedral. (4) Methane is a tetrahedral molecule with the H-C-H bond angles of 109.5 O 

Answer 1

The answer is (3)

1. The carbon and nitrogen are bonded through a triple bond which counts as "one electron pair". Hence the molecule has two electron pairs and is linear. So, it's bond angle will be 180.
2. A formaldehyde molecule is trigonal planar because it has an atom at the end of each electron cloud. H-C-H bond angle is of 120.
3. Water is a bent molecule. The H−O−H angle in water molecule is about 105( due to two lone pair of electron).
4. Methane is a tetrahedral molecule with the H-C-H bond angles of 109.5.