will changing the solvent change the Rf value in chromatography?

Answer 1

Not always, but usually.

The Rf value (ratio of the distance a sample moved to the distance the mobile phased or solvent moved) is dependent upon the stationary phase (the solid in thin layer or paper), the mobile phase, and the chemical nature of the sample.

If the solvent is changed to one more or less polar, then the Rf values of the known and unknown spots will probably change.

Keep in mind that the stationary and mobile phases that are used are usually determined experimentally. The system that gives the best separation between the sample spots is the one usually used. The solvent is one of the items varied.