(a) Select all of the correct statements about the relative acid strengths of pa
ID: 1047891 • Letter: #
Question
(a) Select all of the correct statements about the relative acid strengths of pairs of acids from the choices below. *THERE MAY BE MORE THAN ONE CORRECT STATEMENT
1) HCl is a stronger acid than H2S because Cl is more electronegative than S.
2) H2SO4 is a stronger acid than H2SO3 because it has more oxygens surrounding the central S atom.
3) H2O is a stronger acid than NH3 because O is more electronegative than N.
4) H3PO3 is a stronger acid than H3PO4 because it has fewer oxygens surrounding the central P atom.
5) H2S is a stronger acid than PH3 because S is more electronegative than P.
6) HSO4- is a stronger acid than H2SO4 because it has more charge (is more unstable).
(b) Select ALL of the correct statements about reaction rates from the choices below. *THERE MAY BE MORE THAN ONE CORRECT STATEMENT*
1) The lower the rate of a reaction the longer it takes to reach completion.
2) Solid catalysts do not affect reaction rates.
3) The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step.
4) As a reaction progresses its rate goes down.
5) Reaction rate constants increase with increasing temperature.
7) Reaction rates increase as reactant concentrations decrease.
8) Reaction rates increase as concentrations of homogeneous catalysts increase.
THANKS!!
Explanation / Answer
(a)
1) HCl is a stronger acid than H2S because Cl is more electronegative than S. (TRUE)
2) H2SO4 is a stronger acid than H2SO3 because it has more oxygens surrounding the central S atom. (TRUE)
3) H2O is a stronger acid than NH3 because O is more electronegative than N. (TRUE)
4) H3PO3 is a stronger acid than H3PO4 because it has fewer oxygens surrounding the central P atom. (False more oxygen will stabilize the conjugate base and hence H3PO4 is more acidic)
5) H2S is a stronger acid than PH3 because S is more electronegative than P. (TRUE)
6) HSO4- is a stronger acid than H2SO4 because it has more charge (is more unstable). (False H2SO4 is stronger acid as proton has to come from neutral molecule rather than charged HSO4-)
(b)
1) The lower the rate of a reaction the longer it takes to reach completion. (TRUE)
2) Solid catalysts do not affect reaction rates. (False heterogeneous catalysis do increase the rate of reaction eg. Pd/C hydrogenation)
3) The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step. (TRUE slowest step is the rate determining step)
4) As a reaction progresses its rate goes down. (TRUE As reactant concentration decreases, the frequency of collision between reactants also decreases)
5) Reaction rate constants increase with increasing temperature. (True reaction rate constant depends on temperature)
7) Reaction rates increase as reactant concentrations decrease. (False rate of reaction decreases as explained in point 4)
8) Reaction rates increase as concentrations of homogeneous catalysts increase. (True it will increase but only up to certain extent, and further increase of catalyst concentration will have no effect)
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