Trichloroethylene, a widely used degreasing solvent for machine parts, is produced in a two-step reaction sequence. Ethylene is first chlorinated to yield tetrachloroethane, which is dehydrochlorinated to form trichloroethylene.

C2H4 (g) + 2Cl2 (g) → C2H2Cl4 (l) + H2 (g): AHᵣ⁰ = -385.76 kJ
C2H2Cl4 (l) → C2HCl3 (l) + HCl (g)

The standard heat of formation of liquid trichloroethylene is -276.2 kJ/mol.
Use the given data and tabulated standard heats of formation of ethylene and HCl to calculate the standard heat of formation of tetrachloroethane and the standard heat of reaction for the second reaction.

ΔH°C2H2Cl4(l) = -333,36 kJ/mol

ΔH°r₂ = -35,14 kJ/mol

Explanation:

The ΔH°r of the first reaction is:

ΔH°r = -385,76 kJ/mol = (ΔH°C2H2Cl4(l) + ΔH°H2(g)) - (ΔH°C2H4(g) + 2ΔHCl2 (g))

ΔH°H2(g) = 0 kJ/mol

ΔH°C2H4(g) = 52,4 kJ/mol

Δ°HCl2 (g) = 0 kJ/mol

Replacing:

ΔH°C2H2Cl4(l) = -385,76 kJ/mol + 52,4 kJ/mol = -333,36 kJ/mol

The standard heat of the second reaction is:

ΔH°r₂ = ΔH°C2HCl3(l) + ΔH°HCl(g) - ΔH°C2H2Cl4(l)

Where:

ΔH°C2HCl3(l) = -276,2 kJ/mol; ΔH°HCl(g) = -92,3 kJ/mol; ΔH°C2H2Cl4(l) = -333,36 kJ/mol

Replacing:

ΔH°r₂ = -276,2 kJ/mol -92,3 kJ/mol + 333,36 kJ/mol

ΔH°r₂ = -35,14 kJ/mol

I hope it helps!

a

explanation:

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.