AP Chemistry Semester Exam
Below is an energy-profile diagram for two reactions, A and B. Choose the statements that are correct about the reactions.
1. The energy-profile diagram for reaction B could represent a catalyzed reaction A 2. Reaction B is slower than reaction A 3. The reverse reaction of A has higher activation energy than that for the reverse reaction of B 4. reaction A is slower than reaction B 5. the reverse reaction of B has higher activation energy than that for the reverse reaction of A right answer: c) 1,3, and 4 based on graph
At a certain temperature, the value of the equilibrium constant, K, for the reaction below is 2.0x10^5. What is the value of K for the reverse reaction at the same temperature?
5.0x10^-6
Consider the three acids: HF, HSO4, and H2PO4, which list indicates only conj. bases of these acids above?
F-, SO42-, HPO4 2-
End of Chapter 11 Questions now Chapter 14 Questions
dddd
A catalyst increases the rate of a chemical reaction by __________
decreasing the potential energy of the activated complex
After equilibrium is established for the reaction below, some pure O2 g is injected into the reaction vessel at a constant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its original equilibrium 2SO3 (g) yields 2SO2 (g) + O2 (g)
the amount of SO2 g in the reaction vessel
A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature.
the average speed of the gas molecules remains the same.
Consider the reaction H2 (g)+ I2 (g) yields 2HI The rate law for this reaction has been determined to be Rate=k[H2][I2] Which mechanism is consistent with this rate law?
H2+I2 yields 2HI (slow)
a buffer at a pH< 6
H3PO4 and NaH2PO4
Completely dissociates to give H+ ions
HCl
Will react with Na+ to form a ppt.
HCl HIn KOH NH3 any aceid NH3 will react with Na+ to form a ppt.
For questions 1-4 refer to the aqueous solutions containing 1:1 mole ratios of the following pairs of substances. Assume all concentrations are 1 M The solution with the lowest pH
HCl and NaCl
All 7 strong acids
HCl, HNO3, H2SO4, HBr, HI, HClO3, HClO4
Can be used as an acid base indicator
HIn
One difference between the first and second order reaction is that
the half life of a first order reaction does not depend on concentration of a substance the half-life of a second order reaction does depend on the concentration of a substance.
After the equilibrium represented above is established, some pure O2 (g) is injected into the reaction vessel at a Which of the following statements about the pconstant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its value at the original equilibrium. 2SO3 yields 2 SO2 + O2
The amount of SO2 in the reaction vessel
Which of the following describes how much the rate for this trial of the reaction at a constant temperature changes as [B]approaches .4M
the rate decreases because the concentration of the reactants decreases the chemical equation is 2A (g) + B (g) yields C (g)
Which of the following must be true for a reaction for which the activation energy is the same for both the forward and the reverse reactions?
the reaction order is 0
The following chemical equations are the elementary steps for the reaction between NO and N2 to form N2 and H2o. What determines the rate of the entire reaction?
the slowest reaction N2O2 + H2 yields N2O + H2O
What can be said about the substance at 3.5 atm and 130 C
the substance is a supercritical fluid
on the phase diagram shown above, the coordinates of point _________
this is the point at which solid liquid and gas coexist it is point a.
On the phase diagram shown above the coordinates of point ________ correspond to the critical temperature and pressure
this is the point at which the substance becomes a supper critical fluid point B
Relatively high values for all of the following physical properties are associated with strong intermolecular forces EXCEPT
vapor pressure
Strontium- 90 undergoes radioactive decay with a half life of about 30 years. Approximately how many years will have elapsed before 97% of the Sr-90 in a sample will have decayed?
150 years until 97% decays
The ratio of a certain chemical reaction between substances M and N obeys the rate law Rate= k[M][N]^2. The reaction is first studied with [M] and [N] each 2 x 10^-3 M, the reaction rate will increase by a factor of
8
On the phase diagram shown above, segment, __________ corresponds to the conditions of temperature and pressure under which the solid and gas of the substance are in equilibrium.
AC the line which the solid and gas coexist on the diagram
Given the energy-profile diagram below which of the following phrases could correctly describe the kind of reaction shown
An exothermic reaction, a reaction with two steps in its reaction mechanism (1 and 3 looking at the graph)
Which species in the above equilibrium expression act as basses H2PO4- + H2) yields H3)+ + HPO42-
II and III H2O and HPO42-
Which of the following statements about the process above are true HIO + NH3 yields IO- + NH4+ keq= 4.1x10^-16
IO- is a stronger base than NH3 because the acid that creates IO - is a weak acid creating a strong base while NH3 is only a weak base
Which of the following changes alone would cause a decrease in the value of Keq for the reaction represented above 2NO g + O2 g yields 2NO2 g delta H<0
Increasing the temperature
Which of the following salts contains a basic anion
Li2CO3
8 strong bases
LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
All of the following choices are strong bases EXCEPT
Mg(OH)2 ( RbOH, Ba(OH02, Ca(OH)2 are all strong bases)
partially ionizes to give OH- ions
NH3
The most nearly neutral solution
NH3 and HC2H3O2 ( weak acid and weak base neutralize each other
A buffer at a pH> 8
NH3 and NH4Cl
Questions 5 and 6 refer to the graph below that shows the titration curve that results when 100 mL of .0250 M acetic acid is titrated with .100 M Na OH Which of the following indicators is the best choice for the titration
Phenolphthalein 8.2-10 is the pH range. There is going to be a high ph of the titration b/c NaOH is a strong base and acetic acid is a weak acid
What part of the curve corresponds to the optimum buffer action for the acetic acid. acetate ion pair
Point v the half equivalence point
Based on molecular mass and dipole moment of the five compounds in the table below, which should have the highest boiling point?
Propane,(mass:44,dipole Moment: .1) Dimethylether (mass:46 DM:1.3), Methylchloride (Mass:50 DM:1.9) Acetaldehyde: (mass:44 DM: 2.7) Acetonitrile; (Mass:41 DM:3.9) Right Answer: Acetaldehyde
Which of the following is a correct statement about reaction order?
Reaction order can be determined only by experiment
The experimental data from the reaction A yields products gives these three graphs. What is the most likely order for this reaction
The ln[A] is a strait line graph so the reaction is first order
As this reaction proceeds at constant temperature
The rate of the reaction decreases also the effectiveness of collisions between reactant molecules remains the same
The rate law for the reaction is Rate=k[A][B]^2 Which of the following is not true
The reaction is second order overall ( its actually 3rd order)
Witch .1 M solution would have the lowest boiling point a 1 atm
a)CaCl2 b)CH3OH c)C6H1206 d) (NH4)3PO4 its b
will react with CaCO3 to give CO2 gas
any acid
Which of the following statements correctly explains why solid CO2 is converted directly into gaseous CO2 on the stage at a music concert
b) The triple point for CO2 occurs at 5.1 atm and -57 degrees C
When the substances in the equation below are at equilibrium at pressure P and temperature T, the equilibrium can be shifted to favor the products by CuO (s) + H2 (g) yields Cu(s) + H20 (g) delta H = -2.0 kJ
decreasing the temperature
Cases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation below. The initial pressure of the W g is 1.20 atm and that of X g is 1.60 atm. No y or Z is present initially the experiment is carried out at constant temperature . What is the partial pressure of z when the partial pressure of W g has decreased to 1.0 atm.
do ice and find that the partial pressure of z is .2 atm
The rate of a chemical reaction between substances X and Y is found to follow the rate equation, rate= k[X][Y]^2. If the concentration of Y is halved, what condition would result in keeping the reaction rate constant, assuming no temperature change?
if [X] is quadrupled
Which of the following changes alone would cause a decrease in the value of keq for the reaction represented below 2NO g + O2 g yields 2NO2 g delta H<0
increasing the temp.
which of the following sequences of events occurs as this substance from 0 C to 120 C at a constant pressure of 1.0 atm
read the graph and find that At 40 C an equilibrium between solid, liquid and gas is obtained. Beyond that temp. the substance is only in the gas phase.
What phase is the substance in at 20 degrees C and 2.0 atm
read the graph and find the substance is completely solid