ap chem
A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curvethat results, as shown below. The point at which the pH is closest to that of the strong base being added
E
An unknown acid is dissolved in 25 mL of water and titrated with 0.100 M NaOH. The results are shown in the titration curve above. Which of the following could be the unknown acid?
Glycolic acid, pKa = 3.8
On the basis of the information above, a buffer with a pH = 9 can best be made by using
H2PO4- + HPO42-
A 50.0 mL sample of an acid, HA, of unknown molarity is titrated, and the pH of the resulting solution is measured with a meter and graphed as a function of the volume of 0.100 M NaOH added. At point R in the titration, which of the following species has the highest concentration
HA
Is a strong electrolyte in aqueous solution
HBr(g)
The Lewis electron-dot diagrams of the HClO3 molecule and the HClO2 molecule are shown above at the left and right, respectively. Which of the following statements identifies the stronger acid and correctly identifies a factor that contributes to its being the stronger acid?
HClO3(aq) is the stronger acid because the additional electronegative oxygen atom on the chlorine atom stabilizes the conjugate base.
A 0.1M aqueous solution of which of the acids shown in the table above would have a pH closest to 7.0, and why?
HIOHIO, because IΙ has the lowest electronegativity.
The net ionic equation for the reaction that occurs during the titration of nitrous acid with sodium hydroxide is
HNO2 + OH- → NO2- + H2O
Mixtures that would be considered buffers include which of the following? I. 0.10 M HCl + 0.10 M NaCl II. 0.10 M HF + 0.10 M NaF III. 0.10 M HBr + 0.10 M NaBr
II only
Which of the following indicators is the best choice for this titration?
Indicator: Phenolphthalein pH Range of Color Change: 8.2 - 10.0
How many moles of NaF must be dissolved in 1.00 liter of a saturated solution of PbF2 at 25˚C to reduce the [Pb2+] to 1 x 10-6 molar? (Ksp PbF2 at 25˚C = 4.0 x 10-8)
0.20 Mole
A solution prepared by mixing 10 mL of 1 M HCl and 10 mL of 1.2 M NaOH has a pH of
13
The graph above shows the titration curve that resulted when a sample of 0.1 M monoprotic acid was titrated with a solution of NaOH. Based on the graph, the pKa of the acid is closest to
4
What is the pH of a 1.0 x 10-2-molar solution of HCN? (For HCN, Ka = 4.0 x 10-10.)
4 and 7
In a saturated solution of Zn(OH)2 at 25°C, the value of [OH-] is 2.0 x 10-6 M. What is the value of the solubility-product constant, Ksp, for Zn(OH)2 at 25°C ?
4.0 x 10-18
The acid-dissociation constants of HC3H5O3(aq) and CH3NH3+(aq) are given in the table above. Which of the following mixtures is a buffer with a pH of approximately 3?
A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of 0.1 M NaOH
A student performs an acid-base titration and plots the experimental results in the graph above. Which of the following statements best explains the experimental findings?
A weak acid was titrated with a strong base, as evidenced by the equivalence point at pH > 7.
The pH of solutions of four acids prepared at various concentrations were measured and recorded in the table above. The four acids are, in no particular order, chlorous, hydrochloric, lactic, and propanoic. Which of the four acids listed in the table is hydrochloric acid?
Acid 2
A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curvethat results, as shown below. The point at which the concentrations of the weak acid and its conjugate base are approximately equal
B (Half equivalence point)
Beaker X contains 50mL of distilled water and beaker Y contains 100mL of 1.0MNaCl. Solid AgCl is added to each of the beakers. After thoroughly stirring the contents of the beakers, some solid AgCl remains at the bottom of each beaker, as shown above. Which of the following is true?
Concentration of Ag is greater in beaker X
A 50.0 mL sample of an acid, HA, of unknown molarity is titrated, and the pH of the resulting solution is measured with a meter and graphed as a function of the volume of 0.100 M NaOH added. A student carries out the same titration but uses an indicator instead of a pH meter. If the indicator changes color slightly past the equivalence point, what will the student obtain for the calculated concentration of the acid?
Slightly more than 0.0800 M
Acid-dissociation constants of two acids are listed in the table above. A 20. mL sample of a 0.10 M solution of each acid is titrated to the equivalence point with 20. mL of 0.10 M NaOH. Which of the following is a true statement about the pH of the solutions at the equivalence point?
Solution 1 has a higher pH at the equivalence point because CH3CO2H has the stronger conjugate base
To maximize the yield in a certain manufacturing process, a solution of a weak monoprotic acid that has a concentration between 0.20 M and 0.30 M is required. Four 100. mL samples of the acid at different concentrations are each titrated with a 0.20 M NaOH solution. The volume of NaOH needed to reach the end point for each sample is given in the table above. Which solution is the most suitable to maximize the yield?
Solution C
A 50.0 mL sample of an acid, HA, of unknown molarity is titrated, and the pH of the resulting solution is measured with a meter and graphed as a function of the volume of 0.100 M NaOH added. At which point on the titration curve is [A-] closest to twice that of [HA]?
T
Which of the following statements about the pH of 0.010M HClO4 is correct?
pH=2.00, because [H+]=1.0×10−2M.
Samples of NaF(s) and NH4Cl(s) are dissolved in separate beakers that each contain 100mL of water. One of the salts produces a slightly acidic solution. Which of the following equations best represents the formation of the slightly acidic solution?
NH4+(aq)+H2O(l)⇄NH3(aq)+H3O+(aq)
A 50.0 mL sample of an acid, HA, of unknown molarity is titrated, and the pH of the resulting solution is measured with a meter and graphed as a function of the volume of 0.100 M NaOH added. Which of the following is the best particulate representation of the species (other than H2O) that are present in significant concentrations in the solution at point U in the titration?
One with OH- bubble
A solution is prepared by mixing 50 mL of 1 M NaH2PO4 with 50 mL of 1 M Na2HPO4. On the basis of the information above, which of the following species is present in the solution at the lowest concentration?
PO43−
What part of the curve corresponds to the optimum buffer action for the acetic acid/acetate ion pair?
Point V (half equivalence point
The step-wise dissociation of selenous acid, H2SeO3(aq), is represented by the equations above. Which of the following best helps explain why the value of Ka2Ka2 is so much smaller than the value of Ka1?
Removing the first H+ from H2SeO3(aq) requires less energy than removing the second H+, because the second H+ is removed from a negatively charged species.
The pH of 0.1-molar ammonia is approximately
11
The pH of a solution prepared by the addition of 10. mL of 0.002 M KOH(aq) to 10. mL of distilled water is closest to
11
At 25°C, aqueous solutions with a pH of 8 have a hydroxide ion concentration, [OH-], of
1x10^-6 M
What is the H+(aq) concentration in 0.05 M HCN(aq) ? (The Ka for HCN is 5.0 x 10-10.)
5.0 x 10^-6 M
The value of Kw for water at 0°C is 1×10−15. What is the pOH of water at 0°C?
7.5
How can 100. mL of sodium hydroxide solution with a pH of 13.00 be converted to a sodium hydroxide solution with a pH of 12.00 ?
By diluting the solution by 1 liter water
A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curve that results, as shown below. The point at which the moles of the added strong base are equal to the moles of the weak acid initially present
C
The ionization constant for acetic acid is 1.8 x 10-5; that for hydrocyanic acid is 4 x 10-10. In 0.1 M solutions of sodium acetate and sodium cyanide, it is true that
[OH-] of the sodium acetate solution is less than that of the sodium cyanide solution
What is the molar solubility in water of Ag2CrO4 ? (The Ksp for Ag2CrO4 is 8 x 10-12.)
cube root (2x10^-12) M
Which of the following pairs of mathematical expressions can be used to correctly calculate the pH andpOH of a 0.0015MKOH(aq) solution at 25°C?
pH =14.00−(−log(0.0015))pH=14.00−(−log(0.0015)) and pOH=−log(0.0015)
