15. D is correct, exothermic reactions release heat
I am not sure about 16
Answer:
Ethanol's chemical formula is C2H6O. This chemical formula can also be written as CH3CH2OH or C2H5OH. It is made of nine atoms that include two carbon (C) atoms, six hydrogen (H) atoms, and one oxygen (O) atom.
Explanation:
Substance P replaces X in the compound XY
this is the characteristic of decomposition reaction
%yield = 54.6%
<h3>Further explanation</h3>
Percent yield is the compare of the amount of product obtained from a reaction with the amount you calculated
(theoretical)
General formula:
Percent yield = (Actual yield / theoretical yield )x 100%
<h3 />
Reaction
2ZnS+3O₂ ⇒ 2ZnO+2SO₂
MW ZnS = 97.474 g/mol

MW ZnO = 81.38 g/mol
- mol ZnO (from mol ZnS as limiting reactant, O₂ excess)


Theoretical production = 125.388

Answer:
That would be helium, with a melting point of 0.95 K (-272.20 °C)—although this happens only under considerable pressure (~25 atmospheres). At ordinary pressure, helium would remain liquid even if it could be chilled to absolute zero.