What order of C-H bond lengths do you expect in c2h6,c2h4,c2h2?
Well, when it comes to C-H bond lengths, it's a "short" story. If we focus on the compounds C2H6, C2H4, and C2H2, we find that the bond lengths decrease gradually as we move from C2H6 to C2H4, and then C2H2. So, the order of C-H bond lengths goes like this:
C2H6 - They say it's like a long-distance relationship, so the C-H bonds here are the longest. It's like they're stretching their bond to stay connected.
C2H4 - The C-H bonds in this compound are shorter than in C2H6, but not as short as in C2H2. It's like a comfortable distance, still close but not cramped.
C2H2 - The C-H bonds in this compound are the shortest among the three. They're like two peas in a pod, sticking together closely.
So, to summarize, the order of C-H bond lengths from longest to shortest would be C2H6, C2H4, and C2H2. You could say it's a reflection of their "bonding" preferences!
To determine the order of C-H bond lengths in C2H6, C2H4, and C2H2, we need to consider the hybridization of carbon atoms in each molecule.
In C2H6 (ethane), each carbon atom is sp3 hybridized, which means it forms four sigma bonds with four hydrogen atoms. All C-H bonds in ethane are equivalent, and thus have the same bond length.
In C2H4 (ethylene), each carbon atom is sp2 hybridized, forming three sigma bonds with three hydrogen atoms, and one pi bond with the other carbon atom. The pi bond in C2H4 is formed by the overlapping of p orbitals on each carbon atom. In general, pi bonds are weaker and longer than sigma bonds. Thus, the C-H bond directly involved in the pi bond is weaker and longer than the other two C-H bonds.
In C2H2 (acetylene), each carbon atom is sp hybridized, forming two sigma bonds with two hydrogen atoms, and two pi bonds with the other carbon atom. Similar to C2H4, the C-H bond directly involved in the pi bond is weaker and longer than the other C-H bond in C2H2.
Therefore, we can conclude that the order of C-H bond lengths is as follows:
C2H6 (ethane) > C2H4 (ethylene) > C2H2 (acetylene).
In summary, the order of C-H bond lengths is determined by the hybridization and involvement of the carbon atoms in pi bonds.