Module 4 Post Assessment #14

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Elizabeth Gallmeister 1A
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Module 4 Post Assessment #14

Postby Elizabeth Gallmeister 1A » Mon Jan 14, 2019 4:12 pm

15. The photosynthesis reaction, 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(aq) + 6 O2(g), is endothermic. What effect will the following changes have on the equilibrium composition.
a) Water is added.
b) The partial pressure of CO2 is decreased.

A. a) Decrease [C6H12O6] and [O2], b) Decrease [O2]

B. a) Decrease [C6H12O6] and [O2], b) Increase [O2]

C. a) Increase [C6H12O6] and [O2], b) Decrease [O2]

D. a) Increase [C6H12O6] and [O2], b) Increase [O2]

For (a) I know that adding a reactant will cause a shift left and Increase [C6H12O6] and [O2], but what is the effect of CO2 pressure decreasing? Moles of gas are equal on both sides, so I'm a little confused.

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Re: Module 4 Post Assessment #14

Postby AdityaGuru1H » Mon Jan 14, 2019 4:22 pm

i think that the answer is c. This is because partial pressure can be derived from concentration using p= conc * r* t and so a decrease in partial pressure basically means that the amount of co2 is less so the reaction will go towards reactants and decrease the concentration of o2

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Re: Module 4 Post Assessment #14

Postby Chem_Mod » Mon Jan 14, 2019 4:25 pm

Water being added does not shift the reaction in any particular way because it is a liquid solvent that is in excess. Partial pressure and moles/concentration are all analogous, when thinking about Le Chatelier's Principle. Therefore, if the partial pressure of CO2 (a reactant) is decreased then the reaction will shift to the left to increase the partial pressure of CO2 back to normal.

Fanny Lee 2K
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Re: Module 4 Post Assessment #14

Postby Fanny Lee 2K » Mon Jan 14, 2019 5:15 pm

Adding water to the reactants will cause the yield of the products (in this case C6H12O6 and O2) to increase as well. If the partial pressure of CO2 is decreased, it will cause the products to decrease to make up for the loss of the partial pressure from the reactants.

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