Answer:
-12162.47 joules (or -12000 joules when accounting for significant figures)
Explanation (btw I used 1 cal as 4.184 joules because SI units are better):
q = m c delta T
q = (70.9) (4.184) (25 - 66)
q = (70.9) (4.184) (-41)
q = -12162.47 joules
Most atoms do not. For those atoms that do not have a full valence shell (which usually would contain eight electrons, except for hydrogen and helium, where it would contain two), something has to change. So nature's tendency toward a full valence shell will lead to one of two things: The gain or loss of electrons.
Answer:
the equilibrium concentration of [PCl₅] is 3.64*10⁻³ M
Explanation:
for the reaction
PCl₅(g) → PCl₃(g) + Cl₂(g)
where
Kc= [PCl₃]*[Cl₂]/[PCl₅] = 2.0*10¹ M = 20 M
and [A] denote concentrations of A
if initially the mixture is pure PCl₅ , then it will dissociate according to the reaction and since always one mole of PCl₃(g) is generated with one mole of Cl₂(g) , the total number of moles of both at the end is the same → they have the same concentration → [PCl₃(g)] = [Cl₂]=0.27 M
therefore
Kc= [PCl₃]*[Cl₂]/[PCl₅] = 0.27 M* 0.27 M /[PCl₅] = 20 M
[PCl₅] = 0.27 M* 0.27 M / 20 M = 3.64*10⁻³ M
[PCl₅] = 3.64*10⁻³ M
the equilibrium concentration of [PCl₅] is 3.64*10⁻³ M
