Term test 2 (practise 1)

Question 1

how to rate of change of an element is related to the rate of change of another element

Answer 1

ratio with concentration of reference element on the top and wanted element on the bottom

Question 2

shown below are vessels each with different starting amounts of A, B, and C molecules. What is the rate law for this reaction?

Question 3

what type of graph represents a second-order reaction?

Answer 3

graph going up from low to high

Question 4

the reaction rate for a certain reaction increases by a factor of 10 when temperature is increased from 25 to 75 degrees. what is the activation energy

Answer 4

ln(k1/k2)=-Ea/8.3145*10^3(1/t2-1/t1)

Question 5

for a diagram does the dash line represent a catalyzed version of the potential energy profile for the same reaction?

Answer 5

on the hill of the solid line, below it is an indent of the dashed line

Question 6

given an equilibrium expression, write the equilibrium constant in reverse.

Answer 6

1 write the original equation
2. write reciprocal of original equation

Question 7

a sufficient element is sealed in a flask, the total pressure is if0.117 at equilibrium. what is the value of Kp

Answer 7

1. divide the total pressure by 3 to get the pressure of one substance
2. write out the Kp expression
3. plug numbers into the equation and solve for Kp

Question 8

consider an equilibrium mixture equation. know la chatters principle

Answer 8

if you remove an element on one side, the reaction moves to that side

if you add one element on one side, the reaction moves to the opposite side

the type of stress does not matter

Question 9

what is the value of the equilibrium constant given an equilibrium chemical reaction and the Ka for an element?

Answer 9

1. write the equation of the equilibrium constant
2. use the formula Kw/ka

Question 10

what is the pH given 0.3 M of an acid and the ka value?

Answer 10

1. write out the general equation of an acid
2. make an Ice table
3. write the ka expression
4. plug in numbers from the ICE table and the Ka value into the KA expression and solve for x
5. take the negative log of the x value

Question 11

if equal numbers of the mols of weak acid HCM and base KOH are added to water, the resulting solution is what

Answer 11

basic because the base is stronger than the acid

Question 12

which of the following combinations would make a buffer of pH 3.8 most resistant to change in pH upon the addition of a strong acid? gives the KA of many different acids

Answer 12

find the of each element
pka=-log(ka)
jot down the answer for each element
pick the element closest to the pH given

Question 13

given two elements, find what the main species present are.

Answer 13

1. break up the elements into two ions. using the cross method to find the original species
2. the original species are the main ions present

Question 14

given the concentration of an acid, a base and the Ka value, find the pH

Answer 14

use the herderson hasselbacl equation

ph=pka+log(base/acid)

1. find the pKA using pka=-log(ka)
2. use the pKa and the concentration of the acids and base to find the pH

Question 15

calculate the change in pH if 0.120g of solid NaOH is added to 150 mL of this solution given the concentration of an acid, a base and the Ka value.

Answer 15

1. convert NaOH from grams to moles
2. convert the acid to mols
3. convert the base to moles
4. make an ICE table (subtract the limiting reagent) to find the new mols of acid and base
5. plug the new concentration of the acid and base and the ka value into the Herderson Hasselback equation to find the pH

Question 15

how many mols of a PbCL2 will dissolve in 750 Ml of 0.65M PbNO3 solution? a Ksp value is given

Answer 15

1. make an equation
2. write the ksp expression
3. make an ICE table
4. use the Ksp and the ICe table find the x value
5. since the X value is in molarity, convert molarity to mols using M *L

Question 15

consider the following reaction energy diagram, how many elementary steps are in the reaction mechanism?

Answer 15

count the number of hills

Question 16

indicate the forward and reverse energies on the diagram

Answer 16

1. forward is the distance between the dashed line on the top and the first dent
2. label if EA forward
3. the reverse the the distance between the dashed line on the top and the last hill
4. label it Ea reverse

Question 17

based on the energy diagram does a higher energy for the reaction of products

Answer 17

1. identity if the energy diagram is endothermic or exothermic

if the initial has a lower potential energy than the final the reaction is endothermic

if the initial has a higher potential energy than the final, the reaction is exothermic

say the reaction is exothermic,
2. the reaction will shift to the reactant side because the reaction releases heat and thus there is more activity on the product side

Question 18

propose a reaction mechanism for this reaction that is first order

Answer 18

1. rate the rate law using what is given
   2.