chem unit 9 frq questions and solutions

So, if we conduct the reaction at
CHEM UNIT 9 FRQ QUESTIONS 60°C instead of 25°C, the cell ky
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potential would increase. This is
AND SOLUTIONS because at higher temperatures,
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the equilibrium constant (KeqKeq) ky ky ky ky




goes up, and this contributes to a ky ky ky ky ky ky ky




Sr(s) + Mg2+ <===> Sr2+ + Mg(s) ky ky rise in the standard cell potential ky ky ky ky ky ky ky ky ky ky




Consider the reaction represented above that occurs at 25°C. All reactants (E∘E∘). Therefore, conducting the
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and products are in their standard states.
ky ky reaction at 60°C instead of 25°C ky ky ky ky ky ky ky ky ky ky ky




The value of the equilibrium constant, Keq, for the reaction is 4.2 x 1017 at
ky would result in a higher cell
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25°C.
ky potential. ky




in answer fill out the equation Ecell= ky ky ky ky ky ky




(a) Predict the sign of the standard cell potential, E°, for a cell based on the
ky RT/nF times ln Q to show that cell of
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reaction. Explain your prediction. - answers(a) The standard cell potential will 60> than cell 25
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be positive because the reaction is spontaneous, meaning it naturally occurs.
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This is indicated by the equilibrium constant (Keq) being greater than 1.
ky ky ky Sr(s) + Mg2+ <===> Sr2+ + Mg(s) ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky




Consider the reaction represented ky ky ky




The standard cell potential, which tells us whether a reaction proceeds
ky above that occurs at 25°C. All ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky




spontaneously or not, will be positive. This positivity indicates that the reaction reactants and products are in their
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occurs naturally without needing external energy input. We know this
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because the equilibrium constant (Keq) is greater than 1, showing that the
ky The value of the equilibrium
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reaction heavily favors the formation of products over reactants.
ky constant, Keq, for the reaction is
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4.2 x 1017 at 25°C. ky ky ky ky ky




Sr(s) + Mg2+ <===> Sr2+ + Mg(s) ky ky ky ky ky ky




Consider the reaction represented above that occurs at 25°C. All reactants (d) How would the cell potential
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and products are in their standard states.
ky ky change if the reaction were carried ky ky ky ky ky ky ky ky ky ky ky




The value of the equilibrium constant, Keq, for the reaction is 4.2 x 1017 at
ky out at 25°C with a 1.0-molar
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25°C.
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Mg(NO3)2 and a 0.10-molar ky ky ky




(b) Identify the oxidizing agent for the spontaneous reaction. - answers(b) In solution of Sr(NO3)2? Explain. -
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this reaction, Mg2+2+ acts as the oxidizing agent.
ky ky answersIf we increase the ky ky ky ky ky ky ky ky ky ky




concentration of Mg2+2+, the cell ky ky ky ky ky




In this reaction, the substance responsible for causing another substance to potential will also increase. This is
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lose electrons is called the oxidizing agent. Since Mg2+Mg2+ ions are
ky ky because it pushes the reaction ky ky ky ky ky ky ky ky ky ky ky ky ky ky




causing another species (strontium) to lose electrons, they are acting as the towards the products.
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oxidizing agent in this reaction. Therefore, Mg2+Mg2+ ions are indeed the
ky Alternatively, increasing the
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oxidizing agent in this redox reaction.
ky concentration of Mg2+2+ makes
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the reaction favor products more, ky ky ky ky ky




Sr(s) + Mg2+ <===> Sr2+ + Mg(s) ky ky leading to a higher cell potential. ky ky ky ky ky ky ky ky ky ky




Consider the reaction represented above that occurs at 25°C. All reactants ky ky ky ky ky ky ky ky ky ky




and products are in their standard states.
ky ky Increasing the concentration of ky ky ky ky ky ky ky ky




The value of the equilibrium constant, Keq, for the reaction is 4.2 x 1017 at
ky Mg2+2+ will push the reaction
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25°C.
ky towards the product side, leading ky ky ky ky ky




to an increase in cell potential. This ky ky ky ky ky ky ky




(c) If the reaction were carried out at 60°C instead of 25°C, how would the cell happens because when there's
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potential change? Justify your
ky more Mg2+2+, the reaction tends
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answer. - answersWhen we increase the temperature, the cell potential goes to favor the formation of products.
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up. This happens because the reaction prefers higher temperatures, which
ky ky Alternatively, increasing the
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makes the equilibrium constant increase. Essentially, when we raise the
ky ky concentration of Mg2+2+ makes ky ky ky ky ky ky ky ky ky ky ky ky




temperature, the reaction is more likely to make products rather than staying the reaction favor products more,
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as reactants. It's like giving the reaction a boost of energy to move towards
ky ky leading to a higher cell potential. ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky ky




making more products.
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