Notes
2 A + 2 B <===> C + D
The following data about the reaction above were obtained from three experiments:
| Experiment | [A] | [B] | Initial Rate of Formation of C (mole liter¯1 min¯1) |
| 1 | 0.60 | 0.15 | 6.3 x 10¯3 |
| 2 | 0.20 | 0.60 | 2.8 x 10¯3 |
| 3 | 0.20 | 0.15 | 7.0 x 10¯4 |
(a) What is the rate equation for the reaction?
(b) What is the numerical value of the rate constant k? What are its dimensions?
(c) Propose a reaction mechanism for this reaction.
Br2 + 2 Fe2+(aq) <===> 2 Br¯(aq) + 2 Fe3+(aq)
For the reaction above, the following data are available:
| 2 Br¯(aq) <===> Br2(l) + 2e¯ | E° = -1.07 volts |
| Fe2+(aq) <===> Fe3+(aq) + e¯ | E° = -0.77 volts |
| Substance | S° J mole¯1 K¯1 |
| Br2(l) | 152.3 |
| Fe2+(aq) | -113.4 |
| Br¯(aq) | 80.7 |
| Fe3+(aq) | -293.3 |
Please answer these:
(a) Determine DS°
(b) Determine DG°
(c) Determine DH°
Consider the following melting points in degrees Celsius:
| Alkali metals | m.p. | Halogens | m.p. |
| Li | 181 | F2 | -119 |
| Na | 98 | Cl2 | -101 |
| K | 63 | Br2 | -7 |
| Rb | 39 | I2 | +104 |
| Cs | 29 |
(a) Account for the trend in the melting points of the alkali metals.
(b) Account for the trend in the melting points of the halogens.
(Make sure that your discussion clarifies the difference between the two trends.)
Give the formulas to show the reactants and the products for FIVE of the following chemical reactions. Example: A strip of magnesium is added to a solution of silver nitrate.
Mg + Ag+ ---> Mg2+ + Ag
1. hydrogen gas is passed over hot copper(II) oxide.
2. solid zinc sulfide is heated in an excess of oxygen.
3. a limited amount of liquid bromine is added to an excess of benzene.
4. a solution of diammine silver(I) chloride is treated with dilute nitric acid.
5. metallic copper is heated with concentrated sulfuric acid.
6. sulfur dioxide gas is bubbled into an excess of a saturated solution of calcium hydroxide.
7. manganese(IV) oxide is added to warm, concentrated hydrobromic acid.
8. hydrogen sulfide gas is added to a solution of cadmium nitrate.
A 5.00 gram sample of a dry mixture of potassium hydroxide, potassium carbonate, and potassium chloride is reacted with 0.100 liter of 2.0 molar HCl solution.
(a) A 249 milliliter sample of dry CO2 gas, measured at 22 °C and 740 torr, is obtained from the reaction. What is the percentage of potassium carbonate in the mixture?
(b) The excess HCl is found by titration to be chemically equivalent to 86.6 milliliters of 1.50 molar NaOH. Calculate the percentages of potassium hydroxide and of potassium chloride in the original mixture.
What types of isomerism are possible among the molecules that can be obtained by substituting a chlorine atom and a bromine atom for two of the hydrogen atoms in each of the following?
(a) Ethane, C2H6
(b) Ethene, C2H4
Show structures to illustrate each of the types of isomerism you name for each of these compounds.
A 10.00 milliliter sample of NH3 solution is titrated with a standard HCl solution.
1) An unknown volume of water is added to the HCl solution.
2) An unknown volume of water is added to the 10.00 milliliter sample of NH3 solution.
3) Phenolphthalein is used as the indicator.
For each of these three steps taken during the titration:
(a) State whether it introduces an error into the titration results.
(b) For any of the steps that introduce(s) an error, state whether the titration result will be raised or lowered compared to the result obtained if the error had not been made.
(c) Explain why the result is high or low for each error that you detect.
Given a solution of ammonium chloride. What additional reagent or reagents are needed to prepare a buffer from the ammonium chloride solution?
Explain how this buffer solution resists a change in pH when:
(a) Moderate amounts of strong acid are added.
(b) Moderate amounts of strong base are added.
(c) A portion of the buffer solution is diluted with an equal volume of water.
EXPERIMENTAL MEASUREMENTS
| COMPOUND | Moles of Chloride Precipitated by AgNO3 per mole CrCl3 . 6H2O |
Moles of Water Removed by drying agent per mole of CrCl3 . 6H2O |
Number of ions per "molecule" of complex (from electrical conductivity) |
| Violet | 3 | 0 | 4 |
| Light Green | 2 | 1 | 3 |
| Dark Green | 1 | 2 | 2 |
For each of the three compounds having the same formula, CrCl3 . 6H2O, account for the experimental measurements given above. Show the structural formula for each of the compounds, and relate the structure to the measurements.
(a) How many moles of Ba(IO3)2 is contained in 1.0 liter of a saturated solution of this salt at 25 °C. Ksp of Ba(IO3)2 = 6.5 x 10¯10
(b) When 0.100 liter of 0.060 molar Ba(NO3)2 and 0.150 liter of 0.12 molar KIO3 are mixed at 25 °C, how many milligrams of barium ion remains in each milliliter of the solution? Assume that the volumes are additive and that all activity coefficients are unity.
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