Since the forward reaction is endothermic (heat is consumed in the reaction) that means that the enthalpy change for the forward reaction is a positive value.
Therefore, i would say that the reverse or backward reaction is exothermic (heat is released in the reaction to the sorroundings) and that the enthalpy change is a negative value.
Solution:
mass of the cellulose in the mixture is 0.38g
total mass of the mixture is:
3.35+0.38+8.76
=12.4g
thus the percentage of the cellulose in the mixture is:
mass of the cellulose/total mass of the mixture*100%
0.38/12.4*100%
=3%
