Manganese dioxide oxidises hydrochloric acid to chlorine and gives manganous chloride and water.

Explanation

(a) The skeleton equation is written as
`MnO_(2)+HCl to MnCl_(2)+Cl_(2)+H_(2)O`
(b) Focusing on the oxidation numbers
`overset(+4)(Mn) overset(-2)(O_(2)) +overset(+1)(H) overset(-1)(Cl) to overset(+2)(Mn) overset(-1)(Cl_(2)) +overset(Cl_(2))+overset(+1)(H_(2)) overset(-2)(O)`
(c) Locating atoms undergoing change in oxidation numbers
`overset(+4)(Mn) O_(2)+H overset(-1)(Cl) to overset(+2)(MnCl_(2))+overset(0)(Cl_(2))+H_(2)O`
(d) Determining the change in oxidation number
(e) Cris-crossing these changes in the oxidation numbers
`MnO_(2)+2HCl to MnCl_(2)+Cl_(2)+H_(2)O`
(f) Balancing the atoms other than hydrogen and oxygen
`MnO_(2)+2HCl +2HCl to MnCl_(2)+Cl_(2)+H_(2)PO`
(g) Balancing the atoms hydrogen and oxygen `MnO_(2)+4HCl to MnCl_(2)+Cl_(2)+H_(2)O`
This is balanced equations.