Ratio of hybrid orbitals to pure orbitals involved in bonding in Ethyne molecule is

H-Csp≡Csp-HEach ‘sp’ carbon contains 2 ‘sp’ hybrid orbitals and 2 pure ‘p’ orbitals ;H-atom utilizes its pure ‘s’ orbitals in bonding.Number of ‘sp’ hybrid orbitals = 2×2 = 4Number of pure ‘p’ orbitals     = 2×2 = 4Number of pure ‘s’ orbitals     = 2×1 = 2Ratio of hybrid orbitals to pure orbitals = 4 : 6 = 2 : 3 ;