The values are given in the table below

substance δh°f (kj/mol)
so2 (g) −297
so3 (g) −396
so2cl2 (g) −364
h2so4 (ℓ) −814
h2o (ℓ) −286

the value of δh° for the following reaction is −62.1 kj. what is the value of δh°f for hcl(g)?

so2cl2(g) + 2 h2o(ℓ)→ h2so4(ℓ) + 2 hcl(g)

ΔH°f,HCl = - 92.05 KJ/mol

Explanation:

∴ ΔH°rxn = 62.1 KJ/mol

⇒ - 62.1 KJ/mol = 2 ΔH°f,HCl(g) + ΔH°f,H2SO4(l) - 2 ΔH°f,H2O(l) - ΔH°f,SO2Cl2(g)

⇒ 2 ΔH°f,HCl = - 62.1 KJ/mol + 2 ΔH°f,H2O(l) + ΔH°f,SO2Cl2(g) - ΔH°f,H2SO4(l)

⇒ 2 ΔH°f,HCl = - 62.1 KJ/mol + 2 (-286 KJ/mol) - 364 KJ/mol - (- 814 KJ/mol)

⇒ 2 ΔH°f,HCl = - 62.1 KJ/mol - 572 KJ/mol - 364 KJ/mol + 814 KJ/mol

⇒ 2 ΔH°Δf,HCl(g) = - 62.1 KJ/mol - 122 KJ/mol

⇒ 2 ΔH°f,HCl(g) = - 184.1 KJ/mol

⇒ ΔH°f,HCl(g) = ( - 184.1 KJ/mol ) / 2 = - 92.05 KJ/mol

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.