Chem Test acid/base – Flashcards
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the gas that is produced when alkali metals react with water
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Hydrogen
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if KOH is added to pure water, then pH is
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between 7 and 14
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substances that increase the concentration of hydronium [H₃O⁺]
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acids
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substances that increase the concentration of hydroxide [OH⁻]
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bases
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if an equal amount of KOH and HCl were added to pure water, then pH is
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equal to 7
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if HCl is added to pure water, then pH is
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between 0 and 7
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the concentration equilibrium constant (Kb) for a weak base has
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a nonzero value in its denominator
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the concentration equilibrium constant (Ka) for a strong acid has
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a zero in its denominator
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An aqueous solution has a pH of 2.7 at 298 K. Calculate the pOH of the aqueous solution.
a. 12
b. 9.3
c. 17
d. 11
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d. 11
pH + pOH = 14 → pOH = 14 - pH = 14 - 2.7 = 11.3
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Which of the following is not a strong acid?
a. HClO₄
b. HCl
c. HNO₃
d. H₃AsO₄
e. HBr
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d. H₃AsO₄
strong acids: HBr, HCl, HI, H2SO4, HNO3, HClO4
The correct answer is: H3AsO4
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How many liters of water would be necessary to make a solution with 1 gram of calcium hydroxide and a pH = 10.45?
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convert pH into [OH-] → 14 - pH = 3.55 = pOH = -log[OH-] → 10-pOH = [OH-] → [OH-] = 2.82e-4 M
since Ca(OH)2 gives 2 [OH-] for each formula unit, this means 2.82e-4 / 2 = mol Ca(OH)2 needed per liter = 1.41e-4 mol / L
1 g Ca(OH)2 / 74.1 g / mol Ca(OH)2 = 0.0135 mol Ca(OH)2 given in one gram
0.0135 mol / x L = 1.41e-4 mol / L → x = 0.0135 mol / (1.41e-4 mol / L) = 95.77 L
The correct answer is: 95.77
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A basic solution contains more _____ than ______ .
a. oxygen, hydrogen
b. hydroxide, hydronium
c. hydronium, hydroxide
d. hydrogen, oxygen
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b. hydroxide, hydronium
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Acid solutions taste bitter and basic solutions taste sour.
True or False
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False
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Calculate the hydronium ion concentration [H₃O+] of an aqueous solution, given the concentration of hydroxide ions [OH-] = 1 x 10⁻⁵ M, and the ion constant for water (Kw) = 10⁻¹⁴
a. 10⁻⁴ M
b. 10⁻¹⁹ M
c. 10⁻⁹ M
d. 10⁻¹⁴ M
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c. 10⁻⁹ M
[H3O+][OH-] = Kw = 10-14
[H3O+] = 10-14 / [OH-] = 10-14 / 10-5 = 10-9 M [H3O+]
The correct answer is: 10-9 M
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A neutral solution contains more hydroxide ions (OH-) than hydronium ions (H₃O+).
True or False
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A neutral solution contains an equal concentration of hydroxide ions and hydrogen ions.
these are equal when the solution is neutral. False
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A solution that contains equal concentrations of hydroxide ions (OH-) and hydronium ions (H₃O+) is _____.
a. an acid
b. neutral
c. a base
d. ionized
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b. neutral
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An acidic solution contains more hydroxide ions (OH-) than hydronium ions (H3O+).
True or False
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False
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Given the same concentration, a weak acid produces fewer ions than a strong acid.
True or False
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True
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In solution, strong acids and bases ionize completely, but weak acids and bases ionize only partially.
True or False
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True
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Calculate the pOH of a 0.410 M Ca(OH)2 solution.
a. 13.9
b. 0.178
c. 0.387
d. 0.0862
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Ca(OH)2 → Ba2+ + 2 OH-
0.410 M → 0.820 M OH-
-log[OH-] = pOH = -log(0.82) = 0.0862
The correct answer is: 0.0862
d. 0.0862
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What is the pH of 20.00 g of KOH in 350.0 mL of water?
a. -0.008
b. 1.02
c. 14.01
d. 0.0000045
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c. 14.01
20 g KOH / (56.1 g / mol) = 0.3565 mol KOH / 0.35 L = 1.02 M KOH = [OH-]
-log[OH-] = pOH = -log(1.02) = -0.008
pH + pOH = 14 → pH = 14 - (-0.008) = 14.008
The correct answer is: 14.01
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If a solution has a pOH = 9.23, calculate the molar hydronium concentration [H₃O+]
a. 9.3 · 10⁻³ M
b. 5.9 · 10⁻¹⁰ M
c. 4.8 · 10⁻³M
d. 2.1 · 10⁻⁷ M
e. 1.7 · 10⁻⁵ M
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pOH = -log[OH-] → 10-pOH = [OH-] → 10-9.23 = 5.9e-10 M OH-
Kw = [H3O+][OH-] = 10-14 → [H3O+] = 10-14 / [OH-] → [H3O+] = 10-14 / (5.9 · 10-10)
[H3O+] = 1.7 · 10-5 M
The correct answer is: 1.7 · 10-5 M
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The hydronium ion concentration [H3O+] of a fruit juice is 2.5 · 10⁻⁵ M. What is the pH of the juice?
a. 1.5
b. 5.5
c. 2.5
d. 4.6
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-log[H3O+] = pH → -log(2.5e-5) = 4.6
The correct answer is: 4.6
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An aqueous solution of acid causes litmus paper to turn blue.
True or False
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False
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acids turn litmus paper red
True or False
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True
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bases turn litmus paper blue
True or False
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True
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Calculate pH of an aqueous solution of 8.75 · 10⁻⁷ M HCl.
a. 7.85
b. 7.77
c. 8.61
d. 6.06
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HCl + H2O → Cl- + H3O+
for strong acids (like HCl), the acid ionizes 100% into hydronium, so you can use the starting concentration of acid to find the hydronium formed
pH = -log[H3O+] = -log(8.75e-7) = 6.06
The correct answer is: 6.06
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The relative amounts of hydronium ions (H3O+) and hydroxide ions (OH-) determine whether an aqueous solution is acidic, basic or neutral.
True or False
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acids increase hydronium ions (H3O+) while bases increase hydroxide ions (OH-)
The correct answer is 'True'.
