Can a catalyst alone make a nonspontaneous reaction occur spontaneously Explain why or why not.?

No, a catalyst alone cannot make a nonspontaneous reaction occur spontaneously. A catalyst can only speed up the rate of a reaction by lowering the activation energy, but it cannot change the overall thermodynamics of the reaction. In order for a nonspontaneous reaction to occur spontaneously, the reaction must have a negative change in Gibbs free energy (G) value.