The product formed when HCl and CH2Cl2 react is CH4
H
H-C- H methane structure
H
HCl react with CH2Cl2 to form methane (CH4) and chlorine gas(Cl2)
that is,
2HCl(g) + CH2Cl2(l) = CH4 (g) +2Cl2 (g)
In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed. The distinction between physical and chemical change is not clear cut.
1 is D - double-replacements do not make solid metals
2 is A - to have complete combustion the original compound must ONLY have C, H and O
3 is B - the elemental Mg replaces the H in the HCl
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