January 2023
26 One acid-base theory states that a base is an
(1) H- donor (2) H- acceptor
(3) H+ donor
(4) H+ acceptor
Solution: According to the Bronsted Lowry acid-base theory, acid is a proton (H+) donor and base is a proton acceptor.
Answer: Choice 4 is the correct answer.
27 The acidity or alkalinity of a solution can be measured by its (1) pH value (2) electronegativity value
(3) boiling point (4) freezing point
Solution: The acidity of alkalinity of a solution is measured by the pH value. pH is a scale that tell how acidic the solution is. pH of 0-7 is acidic, 7 is neutral and 7-14 is basic.
Answer: Choice 1 is the correct answer.
August 2022
26 As more NaCl(s) is dissolved in a dilute, unsaturated NaCl(aq) solution, the conductivity of the solution (1) decreases as the ion concentration decreases
(2) decreases as the ion concentration increases
(3) increases as the ion concentration decreases
(4) increases as the ion concentration increases
Explanation: When more solute is dissolved, the concentration of the solution should increase (molarity = moles of solute/ liters of solution). NaCl is an ionic compound that dissociates into ions, which makes the solution capable of conducting electricity. As more NaCl is added, more ions are produced which in turn increases the conductivity of the solution.
Answer: 4
27 Which substance always forms when an Arrhenius acid reacts with an Arrhenius base?
(1) CO2
(2) H2 (3) CH3OH
(4) H2O
Explanation: A reaction between an Arrhenius acid and base always yields water and salt as the products.
Answer: 4
50 Given the equation representing a reaction at equilibrium:
NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
According to one acid-base theory, which pair are the H+ donors?
Solution: Looking from the left to the right, we need to ask ourselves who lost a hydrogen (H+ donor). H2O becomes OH- so it lost a hydrogen was the donor. Now we can do the same thing looking from products to the reactants. NH4+ lost the hydrogen to become NH3.
Answer: 3
June 2022
28 Which term describes an acid according to one acid-base theory?
(1) H+ acceptor
(2) H+ donor
(3) H2 acceptor
(4) H2 donor
Explanation: These terms need to be memorized. According to an acid-base theory, an acid is an H+ (proton) donor while a base is an H+ (proton) acceptor.
Answer: 2
47 Which substance is an electrolyte?
(1) H2
(2) HCl
(3) C6H14
(4) C6H12O6
Solution: Electrolytes are substances that can conduct electricity. These are: metals, ionic compounds (liquid or dissolved in water), acids and bases. The list of most common acids and bases can be found on Table K and Table L on the Reference Table. HCl is an acid and should be an electrolyte. The rest of the compounds are molecular substances which do not conduct electricity.
Answer: 2
48 An indicator is added to an aqueous solution with a pH value of 5.6. Which indicator is paired with its observed color in this solution?
(1) Methyl orange is yellow.
(2) Phenolphthalein is pink.
(3) Bromcresol green is yellow.
(4) Thymol blue is blue.
Solution: Table M on the Reference Table shows a list of indicators and the pH range at which their colors change. Let's take a look at each indicator at the pH value indicated: 5.6
Methyl orange has a pH range of 3.1–4.4 and color change of red to yellow. This means that if the solution's pH is lower than 3.1, the color will be red and above 4.4 the color will be yellow. Since the pH is 5.6 which is above 4.4, yellow color should be expected.
Answer: 1
49 Solution A has a pH value of 2.0 and solution B has a pH value of 4.0. How many times greater is the hydronium ion concentration in solution A than the hydronium ion concentration in solution B?
(1) 10
(2) 2
(3) 100
(4) 4
Explanation: As the pH increases, the concentration of H+ or H3O+ (hydronium ion) decreases and the concentration of OH- (hydroxide ion) increases (solution is becoming more basic and less acidic). How much does the concentration change? Each pH unit is equal to a factor of 10. Going from 2.0 to 4.0 is two units, which would lead to a 10*10= 100 factor.
Answer: 3
January 2020
24 Which compound is an Arrhenius base?
(1) HCl
(2) H3PO4 (3) Ca(OH)2
(4) CH3COOH
Solution: Table L on the Reference Table lists common bases.
Answer: 3
25 In a neutralization reaction, an aqueous solution of an Arrhenius acid reacts with an aqueous solution of an Arrhenius base to produce (1) an ether and water (2) an ether and an alcohol
(3) a salt and water (4) a salt and an alcohol
Solution: a neutralization reaction, an aqueous solution of an Arrhenius acid reacts with an aqueous solution of an Arrhenius base to produce a salt and water
Answer: 3
26 According to one acid-base theory, a base is an
(1) H2 acceptor
(2) H2 donor
(3) H+ acceptor
(4) H+ donor
Solution: According to one acid-base theory, a base is an H+ acceptor while an acid is an H+ donor.
Answer: 3
47 In a titration, 10.0 mL of 0.0750 M HCl(aq) is exactly neutralized by 30.0 mL of KOH(aq) of unknown concentration. What is the concentration of the KOH(aq) solution? (1) 0.0250 M
(2) 0.0750 M
(3) 0.225 M
(4) 0.333 M
Solution: Table T on the Reference Table has the formula for titration which is MaVa = MbVb where Ma = molarity of H+, Mb = molarity of OH–, Va = volume of acid, Vb = volume of base. We are given: Va = 10.0 mL, Ma = 0.0750 M, Vb = 30.0 mL, Mb = ? Now, all we have to do is plug the values into the equation and solve for Mb.
Answer: 1
August 2019
27 What is the color of bromcresol green indicator in a solution with a pH value of 2.0?
(1) blue
(2) green (3) red
(4) yellow
Solution: Table M on the Reference Table lists indicators with their pH value ranges and color changes. Bromcresol green has a pH range for color change of 3.8–5.4 and changes from yellow to blue. This means any pH value under 3.8 will result in the color of yellow and any pH value higher than 5.4 will result in a blue color. The pH given is 2.0 which is under 3.8 value and should result in a yellow color.
Answer: 4
28 Which formula can represent hydrogen ions in an aqueous solution? (1) OH-(aq)
(2) Hg2^2+(aq)
(3) H3O+(aq)
(4) NH4+(aq)
Solution: Hydrogen ions (H+) are also represented by H3O+ (hydronium ions).
Answer:3
48 Which equation represents a neutralization reaction?
(1) 6HClO → 4HCl + 2HClO3 (2) CH4 +2O2 →CO2 + 2H2O (3) Ca(OH)2 + H2SO4 → CaSO4 + 2H2O (4) Ba(OH)2 + Cu(NO3)2 → Ba(NO3)2 + Cu(OH)2
Solution: A neutralization reaction occurs when an acid reacts with a base to produce salt and water. The list of common acids can be found in Table K of the Reference Table while Table L lists common bases.
Answer: 3
June 2019
27 Which substance is an Arrhenius base?
(1) HNO3
(2) H2SO3
(3) Ca(OH)2
(4) CH3COOH
Solution: Table L on the Reference Table lists all the common bases.
Answer: Choice 3
49 Given the equation representing a reversible reaction:
CH3COOH(aq) + H2O(l) ⇌ CH3COO-(aq) + H3O+(aq)
According to one acid-base theory, the two H+ donors in the equation are
(1) CH3COOH and H2O
(2) CH3COOH and H3O+
(3) CH3COO- and H2O
(4) CH3COO- and H3O+
Solution: An H+ donor will lose a hydrogen. We can see CH3COOH loses a hydrogen to become CH3COO- and H3O+ loses an H to become H2O.
Answer: Choice 2
January 2019
26 Which substance is an Arrhenius acid? (1) H2
(2) HCl
(3) KCl
(4) NH3
Solution: The definition of an Arrhenius acid is that it gives off H+ ions when dissolved in water. We can also look at Table K on the Reference Table for the common acids. HCl is listed in Table K.
Answer: 2
27 Which statement describes an electrolyte?
(1) An electrolyte conducts an electric current as a solid and dissolves in water.
(2) An electrolyte conducts an electric current as a solid and does not dissolve in water.
(3) When an electrolyte dissolves in water, the resulting solution conducts an electric current.
(4) When an electrolyte dissolves in water, the resulting solution does not conduct an electric current.
Solution: An electrolyte is a substance that can conduct electricity when dissolved in water.
Answer: 3
28 Which type of reaction occurs when an Arrhenius acid reacts with an Arrhenius base to form a salt and water? (1) combustion
(2) decomposition (3) neutralization
(4) saponification
Solution: When an Arrhenius acid reacts with an Arrhenius base to form a salt and water, the reaction is called neutralization. Saponificaion is a reaction that produces soap. Decomposition is a reaction where one molecule forms several new ones. Combustion (burning) is a reaction where a substance such as organic molecule reacts with oxygen.
Answer: 3
48 The table below shows the molar concentrations of hydronium ion, H3O+, in four different solutions.
Which solution has the highest pH?
(1) A
(2) B
(3) C
(4) D
Solution: The highest pH means the most basic solution. The less the concentration of hydronium ion (H3O+) is, the more basic the solution.
Answer: 4
August 2018
48 Which solution is the best conductor of an electric current?
(1) 0.001 mole of NaCl dissolved in 1000. mL of water
(2) 0.005 mole of NaCl dissolved in 1000. mL of water
(3) 0.1 mole of NaCl dissolved in 1000. mL of water
(4) 0.05 mole of NaCl dissolved in 1000. mL of water
Solution: Solution that has the highest concentration of NaCl dissolved will be the best conductor of electricity. Electricity is the movement of charges. The more NaCl is dissolved in water, the more charges will be produced (Na+ and Cl- ions) and the better electric current will be conducted.
Answer: 3
49 Compared to a 1.0-liter aqueous solution with a pH of 7.0, a 1.0-liter aqueous solution with a pH of 5.0 contains (1) 10 times more hydronium ions
(2) 100 times more hydronium ions
(3) 10 times more hydroxide ions
(4) 100 times more hydroxide ions
Solution: As the pH decreases, the concentration of H+ or H3O+ (hydronium ion) increases and the concentration of OH- (hydroxide ion) decreases (solution is becoming more basic and less acidic). How much does the concentration change? Each pH unit is equal to a factor of 10. Going from pH 7-5 = 2 units, means 10*10 = 100. This means there is 100 time more hydronium ions.
Answer: 2
January 2018
24 Which substance is an Arrhenius acid? (1) HBr
(2) NaBr
(3) NaOH
(4) NH3
Solution: The definition of an Arrhenius acid is that it gives off H+ ions when dissolved in water. This eliminates choice 2 since it does not have any hydrogens. Table L lists common bases. NH3 and NaOH are listed in Table L and can be eliminated as well. Finally, we can also look at Table K on the Reference Table for the common acids as well. HCl is listed in Table K. HBr is an Arrhenius acid similarly to HCl.
Answer: 1
26 Which type of reaction occurs when H+(aq) reacts with OH-(aq)? (1) combustion
(2) decomposition
(3) fermentation
(4) neutralization
Solution: When H+(aq) reacts with OH-(aq), the reaction is called neutralization. Decomposition is a reaction where one molecule forms several new ones. Combustion (burning) is a reaction where a substance such as organic molecule reacts with oxygen. Fermentation is a reaction where sugar reacts with yeast to produce alcohol and carbon dioxide.
Answer: 4
27 According to one acid-base theory, a molecule acts as an acid when the molecule (1) accepts an H+
(2) accepts an OH-
(3) donates an H+
(4) donates an OH-
Solution: According to one acid-base theory, a molecule acts as an acid when the molecule accepts an H+.
Answer:1
47 Why is potassium nitrate classified as an electrolyte? (1) It is a molecular compound. (2) It contains a metal. (3) It can conduct electricity as a solid.
(4) It releases ions in an aqueous solution.
Solution: An electrolyte is a substance that can conduct electricity when dissolved in water. An aqueous solution means dissolved in water.
Answer: 4
48 When the concentration of hydrogen ions in a solution is decreased by a factor of ten, the pH of the solution (1) increases by 1
(2) increases by 10
(3) decreases by 1
(4) decreases by 10
Solution: As the concentration of hydrogen ions decreases, pH increases (solution becomes more basic)! Each 1 pH unit is equal to a factor of 10.
Answer: 1
June 2018
25 The concentration of which ion is increased when LiOH is dissolved in water? (1) hydroxide ion
(2) hydrogen ion
(3) hydronium ion
(4) halide ion
Solution: LiOH is a base. Group 1 or 2 metals with OH are strong bases. Bases produce hydroxide ions when dissolved in water.
Answer: 1
26 Which equation represents neutralization?
(1) 6Li(s) + N2(g) → 2Li3N(s)
(2) 2Mg(s) + O2(g) → 2MgO(s)
(3) 2KOH(aq) + H2SO4(aq) → K2SO4(aq) + 2H2O(l)
(4) Pb(NO3)2(aq) + K2CrO4(aq) →2KNO3(aq) + PbCrO4(s)
Solution: A reaction between a base and an acid which produces salt(ionic compound) and water is called neutralization. Equation 3 is the only reaction where we see water in the products as well as a base and an acid in the reactants. We can find H2SO4 in Table K of the common acids and KOH in Table L of the common bases.
Answer: 3
50 Given the balanced equation representing a reaction: HCl + H2O→H3O+ + Cl-
The water molecule acts as a base because it
(1) donates an H+
(2) accepts an H+ (3) donates an OH-
(4) accepts an OH-
Solution: A base is an H+ acceptor. We can see that H2O became H3O+, which means that it accepted an H+ ion.
Answer: 2
June 2017
30 Which pair of compounds represents one Arrhenius acid and one Arrhenius base? (1) CH3OH and NaOH (2) CH3OH and HCl
(3) HNO3 and NaOH (4) HNO3and HCl
Solution:Table K on the Reference Table lists common acid and Table L on the Reference Table lists common bases. HNO3 is listed in Table K and NaOH is listed in Table L.
Answer: 3
40 Which statement explains why 10.0 mL of a 0.50 M H2SO4(aq) solution exactly neutralizes 5.0 mL of a 2.0 M NaOH(aq) solution?
(1) The moles of H+(aq) equal the moles of OH-(aq).
(2) The moles of H2SO4(aq) equal the moles of NaOH(aq).
(3) The moles of H2SO4(aq) are greater than the moles of NaOH(aq).
(4) The moles of H+(aq) are greater than the moles of OH-(aq).
Solution: In a neutralization reaction, the moles of H+(aq) equal to the moles of OH-(aq) at the equivalence point.
Answer: 1
45 Given the equation representing a reversible reaction: HCO3-(aq) + H2O(l) -> H2CO3(aq) + OH-(aq)
Which formula represents the H+ acceptor in the forward reaction? (1) HCO3-(aq) (2) H2O(l)
(3) H2CO3(aq)
(4) OH-(aq)
Solution: Going from left to right, we can see that HCO3- becomes H2CO3 which means it accepted an H+ ion.
Answer: 1
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