1) Consider the equilibrium: HNO 3 (aq) + H 2 O(l) ? H 3 O + (aq) + NO 2 - (aq)
ID: 821782 • Letter: 1
Question
1) Consider the equilibrium: HNO3(aq) + H2O(l) ? H3O+(aq) + NO2-(aq)
Will the following changes cause the equilibrium to shift to the left or right or will there be no effect?
a. NaOH is added? Blank 1
b. NaNO2 is added? Blank 2
c. HCl is added?
d. H2O is added (Solution is diluted)?
2) Consider the equilibria: Fe3+(aq) + SCN-(aq) ? FeSCN2+(aq) ?H < 0
The iron (III) ion is a faint orange color in solution while the product is a dark red color. Predict whether the color will get darker (shift to the right) or lighter (shift to the left).
To help you answer, here are some chemical reactions involving ions in this equilibrium:
NH3(aq) + H2O(aq) ? NH4+(aq) + OH-(aq)
Fe3+(aq) + Sn2+(aq) ? Sn4+(aq) + Fe2+(aq)
Ag+(aq) + SCN-(aq) ? AgSCN(s)
Fe3+(aq) + 3OH-(aq) ? Fe(OH)3(s)
a. AgNO3 is added? Blank 1
b. SnCl2 is added? Blank 2
c. Aqueous NH3 is added? Blank 3
d. Heat is added? Blank 4
3)Consider the equilibrium: BaSO4(s) ? Ba2+(aq) + SO42-(aq) ?H > 0
What direction will the equilibrium shift (answer "left", "right" or "no effect") if
a. H2SO4 is added? Blank 1
b. BaCl2 is added? Blank 2
c. NaCl is added? Blank 3
d. Heat is added?
4) Consider the equilibrium: [Co(H2O)6]2+(aq) + 4Cl-(aq) ? [CoCl4]2-(aq) + 6H2O(l)
The reactants have a light pink color and the products are deep blue. How will adding sodium chloride affect the equilibrium?
Cannot be determined from the information provided.
Equilibrium is not affected.
Equilibrium shifts to the right (dark blue).
Equilibrium shifts to the left (pink).
5) Consider the equilibriam: CaCO3(s) + H2CO3(aq) ? Ca(HCO3)2(aq) ?H > 0
What effect will each of the following changes have on the equilibrium? Will it shift to the left (toward reactants), to the right (toward products) or will there be no effect? Another equilibrium reaction that you may need to consider:
CO2(g) + H2O(l) ? H2CO3(aq)
a. NaCl is added? Blank 1
b. NaHCO3 is added? Blank 2
c. Heat is added? Blank 3
d. Pressure is reduced? Blank 4
Blank 4
Cannot be determined from the information provided.
b.Equilibrium is not affected.
c.Equilibrium shifts to the right (dark blue).
d.Equilibrium shifts to the left (pink).
5) Consider the equilibriam: CaCO3(s) + H2CO3(aq) ? Ca(HCO3)2(aq) ?H > 0
What effect will each of the following changes have on the equilibrium? Will it shift to the left (toward reactants), to the right (toward products) or will there be no effect? Another equilibrium reaction that you may need to consider:
CO2(g) + H2O(l) ? H2CO3(aq)
a. NaCl is added? Blank 1
b. NaHCO3 is added? Blank 2
c. Heat is added? Blank 3
d. Pressure is reduced? Blank 4
Explanation / Answer
From Wiki Pedia:
Suppose we were to increase the concentration of CO in the system. Using Le Chatelier's principle, we can predict that the amount of methanol will increase, decreasing the total change in CO. If we are to add a species to the overall reaction, the reaction will favor the side opposing the addition of the species. Likewise, the subtraction of a species would cause the reaction to fill the "gap" and favor the side where the species was reduced. "
1. a) If NaOH is added, the H3O+ will be consumed. So to restablish the equillibrium, it has to shift right ( Refer Le Chaitelier Principle http://en.wikipedia.org/wiki/Le_Chatelier's_principle)
b) Left side
c) Left
d) Right
2 a) Adding AgNO3 will increase in Ag+ concentration in the molecule leading more formation of AgSCN (s) and more usage of SCN-. For the desired equillibrium reaction, the concenatration of SCN- has been reducesd. According to Le Chaitelier principle, it will shift equillibrium to left. Overall : Lighter
b) Increment in Sn+2 ion concentration will lead to more formation of Sn+4 formation. It will also affect Fe+3 concentration, as it will also reduce so as to re establish the equillibrium. lesser Fe+3 concentration will shift equillibrium in left direction in desired reaction. Overall: Lighter
c) Aqueous NH3 will lead to more formation of OH- (aq). More the OH- concentration, more will Fe(OH)3 formed and more amount of Fe+3 consumed. Equillibrium will shift to left direction. Overall : Lighter
d) In exothermic reactions, heat is added as product. While increasing the heat will lead the equllibrium to shift left. Hence Overall: Lighter
3 a) Left
b) Left
c) No Effect
d) Right
4 Option C : Adding NaCl will increase more concentration of Cl-. Hence equillibrium will shift to right.
5. a) No effect
b) More HCO3- ions on right side. Hence shift left
c) delta H >0 , so heat is added as a reactant. Adding more heat will shift equillibrium to right
d) From Wikipedia: " If we were to decrease pressure by increasing volume, the equilibrium of the above reaction will shift to the left, because the reactant side has greater number of moles than does the product side. The system tries to counteract the decrease in partial pressure of gas molecules by shifting to the side that exerts greater pressure. Similarly, if we were to increase pressure by decreasing volume, the equilibrium shifts to the right, counteracting the pressure increase by shifting to the side with fewer moles of gas that exert less pressure"
hence left
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