Q.Transform the following word equation into balanced chemical equation and write at least 3 changes that occur at molecular level during this chemical change.
2-Methylpropene + Hydrogen --(catalyst)--> Isobutane

Step 1. Write the balanced equation. 2-Methylpropene is CH2=C(CH3)2; hydrogenating it with H2 over Pt or Pd (room temperature) or Ni (high temperature and pressure) gives isobutane: CH2=C(CH3)2 + H2 --Pt/Pd or Ni--> CH3-CH(CH3)-CH3. The equation is already balanced as written (4 carbons and 8 hydrogens on the alkene side plus 2 more H from H2 equal the 10 hydrogens of isobutane, C4H10).

Step 2. Change 1 -- the pi bond breaks. The C=C double bond consists of one sigma bond plus one pi bond; hydrogenation breaks specifically the weaker pi bond, converting the double bond into a single (sigma-only) C-C bond.

Step 3. Change 2 -- rehybridisation. Both carbons that were part of the double bond were sp2-hybridised (planar, 120-degree bond angles); once the pi bond is gone and each carbon gains a new substituent (an H atom), both carbons rehybridise to sp3 (tetrahedral, ~109.5-degree bond angles). …

Writing the balanced hydrogenation equation, then breaking down the bond-level events (pi-bond cleavage, rehybridisation, new sigma-bond fo …

• Writing an unbalanced or mis-structured product (e.g. forgetting isobutane is a branched C4H10, not n-butane). …