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posted by  Labroska on 10/2/2008 4:50:30 PM  |  status: Live  

Exercise 14.70: Problems by Topic - Le Chatelier's Principle

Course Textbook Chapter Problem
General Chemistry N/A CH.14 70
,b)the formation of less hydrogen gas,c)no effect on the quantity of hydrogen gas
2)adding more {\rm{H}}_2 {\rm{O}} to the reaction mixture
a)the formation of additional hydrogen gas,b)the formation of less hydrogen gas,c) 
3)raising the temperature of the reaction mixture
a) 
,b)the formation of less hydrogen gas,c)no effect on the quantity of hydrogen gas
4)increasing the volume of the reaction mixture
a)the formation of additional hydrogen gas,b)the formation of less hydrogen gas,c) 
Question Details:
Coal can be used to generate hydrogen gas (a potential fuel) by the following endothermic reaction.
{\rm{C}}\left( s \right)\; + \;{\rm{H}}_2 {\rm{O}}\left( g \right)\; \rightleftharpoons \;{\rm{CO}}\left( g \right)\; + \;{\rm{H}}_2 \left( g \right)
If this reaction mixture is at equilibrium, predict whether each of the following will result in the formation of additional hydrogen gas, the formation of less hydrogen gas, or have no effect on the quantity of hydrogen gas
1)adding more {\rm C} to the reaction mixture
a) 
the formation of additional hydrogen gas no effect on the quantity of hydrogen gas the formation of additional hydrogen gas no effect on the quantity of hydrogen gas
5)adding a catalyst to the reaction mixture
a)the formation of additional hydrogen gas,b)the formation of less hydrogen gas,c) 
no effect on the quantity of hydrogen gas
 
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posted by Ricky Wilkins on 10/3/2008 4:51:32 AM  |  status: Live
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Labroska's comment:
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 1 ) the answer is a)be cause  according to Lechatelier principle If the concentration of the reactants increases causes the equillibrium shifts tiwards the leass concentration.(to wards products.)
 2) The answer is a)
 3) For endo thermic reaction the eqiullibrium shifts towards the products,if the temparature increases.Thus the answer is a) ,i.e the formation additinal H2 gas.
 4) If the volume of the reaction mixture increases ,the pressue is decreases ,thus the equillibrium shifts to the ffewer number of moles.But here the number of moles on both sides are the same.Hence there is no effect on the equillibrium.
 5) not effect on the equillibrium.
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posted by Ainala8055 on 10/3/2008 5:13:12 AM  |  status: Live
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1--> a)increase in the concentration of reactants cause shift in equilibrium towards products(less conc)
 2)----->a)
 3) For endothermic reaction the eqiullibrium shifts towards the products,if the temparature increases.Thus the answer is a) ,i.e the formation additinal H2 gas.
 4) If the volume of the reaction mixture increases ,the pressue is decreases ,thus the equillibrium shifts to side with less number of moles.But here the number of moles on both sides are the same.Hence there is no effect on the equillibrium.
 5) not effect on the equillibrium
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posted by Anonymous on 10/3/2008 9:08:24 AM  |  status: Live
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Le chatelier principle

If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or total pressure, then the equilibrium shifts to partially counter-act the imposed change.
 Effect of concentration
 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.
Effect of temperature
According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change. since above eqation is endothermic, so on increasing temperature, the position of equilibrium will move so that the temperature is reduced again. It means reaction will go right side and on decreasing temperature reaction will go left side.
 
Effect of pressure
 
An increase in  volume causes the reaction to shift to the side with the fewer moles of gas. A decrease in volume causes the reaction to shift to the side with more moles of gas
Effect of catalyst
 
A catalyst just gets you to equilibrium faster, it doesn't affect the final position of equilibrium like changing the concentration would.
 
 
1) adding more {\rm C} to the reaction mixture
the formation of additional hydrogen gas
 
2)adding more {\rm{H}}_2 {\rm{O}} to the reaction mixture
the formation of additional hydrogen gas
 
3)raising the temperature of the reaction mixture
the formation of additional hydrogen gas
 
4)increasing the volume of the reaction mixture
no effect on the quantity of hydrogen gas
 
5)adding a catalyst to the reaction mixture
 no effect on the quantity of hydrogen gas
 
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