During a certain chemical reaction, the temperature gradually increases.
Which statement best describes this process?
A. It is combustion.
B. It is endothermic.
C. It is a closed system.
D. It is exothermic.

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Given the following at 25c calculate delta hf for hcn (g) at 25c. 2nh3 (g) +3o2 (g) + 2ch4 (g) > 2hcn (g) + 6h2o (g) delta h rxn= -870.8 kj. delta hf=-80.3 kj/mol for nh3 (g), -74.6 kj/mol for ch4, and -241.8 kj/mol for h2o (g)