How can you prove that mercury oxide and chalk are complex substances? What phenomena (physical or chemical) will this proof be based on?

bystudin | November 9, 2020 | Education

Complex substances consist of atoms of different elements, therefore, when they decompose, new substances can be obtained. This phenomenon is based on a chemical phenomenon.
Decomposition of mercury (II) oxide is orange. observes a color change to black – mercury is formed, and a gas is also released – oxygen.
2HgO = 2Hg + O2
When chalk decomposes, carbon dioxide is released:
CaCO3 = CaO + CO2

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