Couple of Gen Chem Rate Questions

[xjoohn]

Hello could anyone answer these for me?

1) Two reactions with different activation energies have the same rate at room temperature. Which
statement correctly describes the rates of these two reactions at the same, higher temperature?
(A) The reaction with the larger activation energy will be faster.
(B) The reaction with the smaller activation energy will be faster.
(C) The two reactions will continue to occur at the same rates.
(D) A prediction cannot be made without additional information.
Answer: A

Thanks

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[amy_k]

For the first question, the two reactions withe different Ea have the same rate at room temperature, this is key. If we start at room temperature and increase the temperature, the rate for both reactions will increase, but the reaction rate for the one with the higher Ea will increase much more because now the increased temperature causes many more reactant particles to have sufficient energy for the reaction to occur whereas the reactants in the lower Ea reaction already had sufficient energy.

 

[amy_k]

For #13 if you look at the units they are asking for reaction rate in mol*L^-1*s^-1

We already have mol*L^-1 which is M, the y axis, and 's' is the x axis so find the initial slope of the line by dividing ΔM/Δs

 

[EParker37]

#26 is also very simple, find the two points that are on both axes. They made it pretty obvious that you just find the point at 40mmHg and 20mmHg and just guesstimate the elapsed time.

 

[amy_k]

For #21 - the rate determining step of a reaction is the slow step, and if we are given rate = k[H2S][Cl2] then both H2S and Cl2 must be reactants in the rate determining step, you should be able to figure out if the first reaction is consistent or not from that.
http://chemwiki.ucdavis.edu/Physica...aws/Reaction_Mechanisms/Rate-Determining_Step
The second reaction is trickier, from the slow step we would get a rate dependent on [Cl2] and [HS-], but HS- isn't a starting material, it is dependent on [H2S] from the first reaction so we substitute [H2S] instead of [HS-] in the reaction rate equation.

 

[amy_k]

OP you should be able to figure these all out now