Question

calculate the enthalpy change for the allotropic transformation of sulphur in the monoclinic form to sulphur in the rhombic form from the following data's
1.S+oxygen gives sulphurdioxide,Delta H is equal to-295.1KJ
2.sulphur +oxygen gives sulpherdioxide,Delta H is equal to -296.KJ

Answer 1

Note: Data is the plural of datum. Apostrophe not needed.
Let Sr = sulfur rhombic and Sm = sulfur monoclinic.
You don't specify which is which; however, check your data.
I found Sr + O2 ==> SO2(g) dH = -296.06
......... Sm + O2 --> SO2(g) dH = -296.36.

If we assume your data to be mean #1 is monoclinic

.........Sm + O2 ==> SO2(g) dH = -295.1 and #2 to be rhombic so
........Sr + O2 ==> SO2(g) dH = -296.

Take equation 1 and add to the reverse of equation 2 like this.
.............Sm + O2 ==> SO2(g) dH = -295.1
.............SO2(g) ==> Sr + O2 dH = +296
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...........Sm ==> Sr -295.1 + 296 = +?
If I have assumed incorrectly you can easily change the two equations and get your answer. Again, please check your numbers.