A3.540-g sample of an unknown metal m is burned in the presence of excess oxygen, producing the oxide m2o3(s) and liberating 18.56 kj of heat at constant pressure. what is the identity of the metal? 4m(s) + 3o2(g) → 2m2o3(s) substanceδh°f (kj/mol) yb2o3(s)–1814.6 tb2o3(s)–1865.2 sm2o3(s)–1823.0 sc2o3(s)–1908.8 y2o3(s)–1905.3 a) sm b) tb c) y d) sc e) yb

a) Sm

Explanation:

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This substantiation could be done by knowing how to compute the released energy for 1 mol the oxide. Thus, for Sm, the computation turns out into:

The sign just indicates that the heat is released due to the chemical reaction and it matches with the indicated heat in the statement.

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i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.