Chem equilibrium module 4, Question #13?

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Adriana Rangel 1A
Posts: 96
Joined: Fri Sep 29, 2017 7:04 am

Chem equilibrium module 4, Question #13?

Postby Adriana Rangel 1A » Sun Nov 26, 2017 3:59 pm

13. State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs.
2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1
i. The volume of the system is compressed. 
ii. The temperature of the system is decreased.

A. i = Products, ii = Products

B. i = Products, ii = Reactants

C. i = Reactants, ii = Neither

D. i = Products, ii = Neither

PART A: I watched the module and am EXTREMELY confused? When the volume of the system decreases and the pressure increases then the concentration of everything increases right? So you're supposed to look at the number of moles on each side (or no?) but then both sides have the same number of moles? So where does the equilibrium shift I am so confused.

PART B: A negative delta H means the chemical reaction is exothermic since heat is being released. In exothermic reactions when temperature decreases then reactant formation is favored. Since more reactants are being formed then will the equilibrium shift towards products to create more products??? I'm kinda confused on this too I am not sure if I am right.

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

Re: Chem equilibrium module 4, Question #13?

Postby Shawn Patel 1I » Sun Nov 26, 2017 5:00 pm

For part A, you have the correct reasoning, but on the right side of the reaction, you have I2(s), which is a solid. You only have to check for the most amount of gas moles in the reaction, not including solids or liquids.

For part B, when the reaction is exothermic, and the heat is decreased, product formation is favored, but if the heat increases, reactant formation is favored.

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