The inversion of cane sugar (sucrose) is an acid catalysed hydrolysis reaction which can be represented as,
This is a bimolecular reaction.
Hence,
The true rate law for the reaction should be,
Rate = k[C12H22O11] [H2O].
This shows that the reaction should be second order.
Since water (H2O) is in large excess, its concentration remains constant and the rate depends only upon the concentration of cane sugar.
Rate = k[C12H22O11]
Therefore,
The second order true rate law becomes first order rate law.
Hence,
The inversion of cane sugar is a pseudo first order reaction.