DP Chemistry Questionbank

Which species acts as a Lewis and Brønsted–Lowry base?

A.      [Al(H₂O)₆]³⁺

B.      BF₃

C.      NH₄⁺

D.      OH⁻

Identify the amphiprotic species.

Identify one conjugate acid-base pair in the reaction.

Calculate the amount, in mol, of NaOH(aq) used.

A student working in the laboratory classified HNO₃, H₂SO₄, H₃PO₄ and HClO₄ as acids based on their pH. He hypothesized that “all acids contain oxygen and hydrogen”.

Evaluate his hypothesis.

Write an equation to show ammonia, NH₃, acting as a Brønsted–Lowry base and a different equation to show it acting as a Lewis base.

Which classification is correct for the reaction?

H₂PO₄⁻(aq) + H₂O(l) → HPO₄²⁻(aq) + H₃O⁺(aq)

Outline why H₃PO₄/HPO₄²⁻ is not a conjugate acid-base pair.

Which two species act as Brønsted–Lowry acids in the reaction?

H₂PO₄⁻ (aq) + OH⁻ (aq) $\rightleftharpoons$ HPO₄²⁻ (aq) + H₂O (l)

A. HPO₄²⁻ (aq) and OH⁻ (aq)

B. H₂PO₄⁻ (aq) and HPO₄²⁻ (aq)

C. HPO₄²⁻ (aq) and H₂O (l)

D. H₂PO₄⁻ (aq) and H₂O (l)

State the equation for the reaction of each substance with water.

State the equation for the reaction of each substance with water.

Draw the structure of the conjugate base of benzoic acid showing all the atoms and all the bonds.

The hydrogencarbonate ion, produced in Equilibrium (2), can also act as an acid.

State the formula of its conjugate base.

The reaction of the hydroxide ion with carbon dioxide and with the hydrogencarbonate ion can be represented by Equations 3 and 4.

Equation (3)     OH⁻ (aq) + CO₂ (g) → HCO₃⁻ (aq)
Equation (4)     OH⁻ (aq) + HCO₃⁻ (aq) → H₂O (l) + CO₃²⁻ (aq)

Discuss how these equations show the difference between a Lewis base and a Brønsted–Lowry base.

Equation (3):

Equation (4):

Draw the structure of the conjugate base of benzoic acid showing all the atoms and all the bonds.

The hydrogencarbonate ion, produced in Equilibrium (2), can also act as an acid.

State the formula of its conjugate base.

Which of these acids has the weakest conjugate base?

A.  $\mathrm{HCl}$

B.  ${\mathrm{CH}}_3\mathrm{COOH}$

C.  ${\mathrm{NH}}_4\mathrm{Cl}$

D.  ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$

Which species is a Lewis acid but not a Brønsted–Lowry acid?

A.  ${\mathrm{Cu}}^{2+}$

B.  ${{\mathrm{NH}}_4}^{+}$

C.  $\mathrm{Cu}$

D.  ${\mathrm{CH}}_3\mathrm{COOH}$

State the formula of the conjugate base of hypochlorous acid.

State the formula of the conjugate base of hypochlorous acid.

Calculate the $K_{\mathrm{b}}$ of the conjugate base of ethanoic acid using sections 2 and 21 of the data booklet.

Which is a Lewis acid, but not a Brønsted-Lowry acid?

A.  ${\text{BF}}_3$

B.  ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$

C.  ${\text{NH}}_3$

D.  ${\text{Cl}}^{-}$

Formulate an equation for the reaction of one mole of phosphoric acid with one mole of sodium hydroxide.

Formulate two equations to show the amphiprotic nature of H₂PO₄⁻.

Formulate an equation for the reaction of one mole of phosphoric acid with one mole of sodium hydroxide.

Formulate two equations to show the amphiprotic nature of H₂PO₄⁻.

5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)₂•2H₂O, was dissolved in water to make 1.00 dm³ of solution. 25.0 cm³ samples of this solution were titrated against a 0.100 mol dm^-3 solution of sodium hydroxide using a suitable indicator.

(COOH)₂ (aq) + 2NaOH (aq) → (COONa)₂ (aq) + 2H₂O (l)

The mean value of the titre was 14.0 cm³.

(i)   Calculate the amount, in mol, of NaOH in 14.0 cm³ of 0.100 mol dm^-3 solution.

(ii)  Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm³ sample.

(iii) Determine the percentage purity of the hydrated ethanedioic acid sample.

5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)₂•2H₂O, was dissolved in water to make 1.00 dm³ of solution. 25.0 cm³ samples of this solution were titrated against a 0.100 mol dm^-3 solution of sodium hydroxide using a suitable indicator.

(COOH)₂ (aq) + 2NaOH (aq) → (COONa)₂ (aq) + 2H₂O (l)

The mean value of the titre was 14.0 cm³.

(i) Suggest a suitable indicator for this titration. Use section 22 of the data booklet.

(ii) Calculate the amount, in mol, of NaOH in 14.0 cm³ of 0.100 mol dm^-3 solution.

(iii) Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm³ sample.

(iv) Determine the percentage purity of the hydrated ethanedioic acid sample.

Suggest one disadvantage of using this smoke in an enclosed space.

Deduce why more heat was produced in mixture B than in mixture A.

Deduce why the temperature is higher in mixture C than in mixture D.

Some oxides of period 3, such as Na₂O and P₄O₁₀, react with water. A spatula measure of each oxide was added to a separate 100 cm³ flask containing distilled water and a few drops of bromothymol blue indicator.

The indicator is listed in section 22 of the data booklet.

Deduce the colour of the resulting solution and the chemical formula of the product formed after reaction with water for each oxide.

State a technique other than a pH titration that can be used to detect the equivalence point.

State an equation for the reaction of magnesium hydroxide with hydrochloric acid.

Outline, using an equation, why sodium ethanoate is basic.

Activity series of selected elements:

$$\text{greatest activity}\stackrel{\text{K, Ca, Al, Fe, H, Cu, Ag, Au}}{\leftarrow }\text{least activity}$$

Which react with dilute sulfuric acid?

       I.     Cu

       II.     CuO

       III.     CuCO₃

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

With which do most acids react?

   I. sodium hydrogen carbonate
   II. magnesium
   III. calcium sulfate

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

An antacid contains calcium carbonate and magnesium carbonate.

Write the equation for the reaction of magnesium carbonate with excess stomach acid.

Which substance will not produce copper(II) chloride when added to dilute hydrochloric acid?

A.  $\mathrm{Cu} \left(\mathrm{s}\right)$

B.  $\mathrm{Cu}\left(\mathrm{OH}{)}_2 \right(\mathrm{s})$

C.  ${\mathrm{CuCO}}_3 \left(\mathrm{s}\right)$

D.  $\mathrm{CuO} \left(\mathrm{s}\right)$

State the $K_{\mathrm{a}}$ expression for ethanoic acid.

Potassium hydroxide solutions can react with carbon dioxide from the air. The solution was made one day prior to using it in the titration.

Predict, giving a reason, the effect of this error on the calculated concentration of ethanoic acid in 5(e).

An additional experiment was conducted in which only the sulfuric acid catalyst was titrated with $\mathrm{NaOH}\hspace{0.17em}\left(\mathrm{aq}\right)$. Outline why this experiment was necessary.

What happens to the amount of hydroxide ions and hydroxide ion concentration when water is added to a solution of NH₃(aq)?

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

What is the pH of 1.0 × 10⁻³ mol dm⁻³ sodium hydroxide, NaOH(aq)?

K_w = 1.0 × 10⁻¹⁴

A.     3

B.     4

C.     10

D.     11

Calculate [H⁺] in the NaOH solution.

What will happen if the pressure is increased in the following reaction mixture at equilibrium?

CO₂ (g) + H₂O (l) $\rightleftharpoons$ H⁺ (aq) + HCO₃⁻ (aq)

A. The equilibrium will shift to the right and pH will decrease.

B. The equilibrium will shift to the right and pH will increase.

C. The equilibrium will shift to the left and pH will increase.

D. The equilibrium will shift to the left and pH will decrease.

Which statement is incorrect for a 0.10 mol dm^–3 HCOOH solution?

A. pH = 1

B. [H⁺] << 0.10 mol dm^–3

C. [HCOO^–] is approximately equal to [H⁺]

D. HCOOH is partially ionized

Outline why pH is more widely used than [H⁺] for measuring relative acidity.

A 0.250 mol dm⁻³ aqueous solution of butanoic acid has a concentration of hydrogen ions, [H⁺], of 0.00192 mol dm⁻³. Calculate the concentration of hydroxide ions, [OH⁻], in the solution at 298 K.

The pH of an aqueous solution of benzoic acid at 298 K is 2.95. Determine the concentration of hydroxide ions in the solution, using section 2 of the data booklet.

Predict, referring to Equilibrium (2), how the added sodium hydrogencarbonate affects the pH.(Assume pressure and temperature remain constant.)

Which solution is basic at 25 °C?

K_w = 1.0 × 10⁻¹⁴

A. [H⁺] = 1.0 × 10⁻³ mol dm⁻³

B. [OH⁻] = 1.0 × 10⁻¹³ mol dm⁻³

C. solution of pH = 4.00

D. [H₃O⁺] = 1.0 × 10⁻¹³ mol dm⁻³

What is the pH of 0.001 mol dm⁻³ NaOH (aq)?

A. 1

B. 3

C. 11

D. 13

The pH of an aqueous solution of benzoic acid at 298 K is 2.95. Determine the concentration of hydroxide ions in the solution, using section 2 of the data booklet.

Predict, referring to Equilibrium (2), how the added sodium hydrogencarbonate affects the pH.(Assume pressure and temperature remain constant.)

Which solution is basic at 25 °C?

K_w = 1.0 × 10⁻¹⁴

A. [H⁺] = 1.0 × 10⁻³ mol dm⁻³

B. [OH⁻] = 1.0 × 10⁻¹³ mol dm⁻³

C. solution of pH = 4.00

D. [H₃O⁺] = 1.0 × 10⁻¹³ mol dm⁻³

What is the pH of 0.001 mol dm⁻³ NaOH (aq)?

A. 1

B. 3

C. 11

D. 13

Calculate the pH of a buffer solution which contains 0.20 mol dm⁻³ ethanoic acid and 0.50 mol dm⁻³ sodium ethanoate. Use section 1 of the data booklet.

pK_a (ethanoic acid) = 4.76

Explain why a change in pH affects the tertiary structure of an enzyme in solution.

Which apparatus can be used to monitor the rate of this reaction?

${\mathrm{CH}}_3{\mathrm{COCH}}_3 \left(\mathrm{aq}\right)+{\mathrm{I}}_2 \left(\mathrm{aq}\right)\to {\mathrm{CH}}_3{\mathrm{COCH}}_2\mathrm{I} \left(\mathrm{aq}\right)+{\mathrm{H}}^{+} \left(\mathrm{aq}\right)+{\mathrm{I}}^{-} \left(\mathrm{aq}\right)$

1. A pH meter
2. A gas syringe
3. A colorimeter
   

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

What is the pH of an ammonia solution that has $\left[{\mathrm{OH}}^{-}\right]=1\times {10}^{-4} \mathrm{mol} {\mathrm{dm}}^{-3}$?

A.  $4.0$

B.  $8.0$

C.  $10.0$

D.  $12.0$

Calculate the concentration of ${\mathrm{H}}^{+} \left(\mathrm{aq}\right)$ in a $\mathrm{HClO} \left(\mathrm{aq}\right)$ solution with a $\mathrm{pH}=3.61$.

Calculate the concentration of ${\mathrm{H}}^{+} \left(\mathrm{aq}\right)$ in a $\mathrm{HClO} \left(\mathrm{aq}\right)$ solution with a $\mathrm{pH}=3.61$.

Which solution has a pH of 9?

A.  1.0 × 10⁻⁹ mol dm⁻³ $\text{HCl}$ (aq)

B.  1.0 × 10⁻⁵ mol dm⁻³ $\text{KOH}$ (aq)

C.  1.0 × 10⁻⁹ mol dm⁻³ $\text{KOH}$ (aq)

D.  1.0 × 10⁻⁵ mol dm⁻³ $\text{HCl}$ (aq)

Saturated calcium hydroxide solution is used to test for carbon dioxide. Calculate the pH of a 2.33 × 10⁻²mol dm⁻³ solution of calcium hydroxide, a strong base.

Saturated calcium hydroxide solution is used to test for carbon dioxide. Calculate the pH of a 2.33 × 10⁻²mol dm⁻³ solution of calcium hydroxide, a strong base.

What is the pH of 0.01 mol dm⁻³ KOH (aq)?

A.  1.0

B.  2.0

C.  12.0

D.  13.0

Which of the 0.001 mol dm⁻³ solutions is most likely to have a pH of 11.3?

A.  Ca(OH)₂(aq)

B.  H₃PO₄(aq)

C.  NaOH (aq)

D.  NH₄OH (aq)

Calculate the concentration of hydroxide ions in an ammonia solution with pH = 9.3. Use sections 1 and 2 of the data booklet.

Calculate the concentration of hydroxide ions in an ammonia solution with pH = 9.3. Use sections 1 and 2 of the data booklet.

Which 1.0 mol$$dm^–3 solution has the highest pH?

A.     Ammonium chloride

B.     Sulfuric acid

C.     Sodium chloride

D.     Ammonia

Hydrazine reacts with water in a similar way to ammonia. Deduce an equation for the reaction of hydrazine with water.

Outline, using an ionic equation, what is observed when magnesium powder is added to a solution of ammonium chloride.

State a technique other than a pH titration that can be used to detect the equivalence point.

Oceans can act as a carbon sink, removing some CO₂(g) from the atmosphere.

CO₂(g) $\rightleftharpoons$ CO₂(aq)

Aqueous carbon dioxide, CO₂(aq), quickly reacts with ocean water in a new equilibrium reaction. Construct the equilibrium equation for this reaction including state symbols.

Describe how large amounts of CO₂ could reduce the pH of the ocean using an equation to support your answer.

Identify the other product formed.

Predict, giving a reason, a difference between the reactions of the same concentrations of hydrochloric acid and ethanoic acid with samples of calcium carbonate.

Predict, giving a reason, a difference between the reactions of the same concentrations of hydrochloric acid and ethanoic acid with samples of calcium carbonate.

State and explain the effect on the rate of reaction if ethanoic acid of the same concentration is used in place of hydrochloric acid.

What is the order of increasing pH for the following solutions of the same concentration?

A.   HCl (aq) < NH₃ (aq) < NaOH (aq) < CH₃COOH (aq)

B.   CH₃COOH (aq) < HCl (aq) < NH₃ (aq) < NaOH (aq)

C.   HCl (aq) < CH₃COOH (aq) < NH₃ (aq) < NaOH (aq)

D.   NaOH (aq) < NH₃ (aq) < CH₃COOH (aq) < HCl (aq)

State the equation for the reaction of each substance with water.

State the equation for the reaction of each substance with water.

Outline why ethanoic acid is classified as a weak acid.

Distinguish between a weak and strong acid.

Weak acid: 

Strong acid: 

Outline why ethanoic acid is classified as a weak acid.

Distinguish between a weak and strong acid.

Weak acid: 

Strong acid:

The dissociation of citric acid is an endothermic process. State the effect on the hydrogen ion concentration, [H⁺], and on K_a, of increasing the temperature.

Identify the compound responsible for the acidity of gastric juice, and state whether it is a strong or weak acid.

The dissociation of citric acid is an endothermic process. State the effect on the hydrogen ion concentration, [H⁺], and on the equilibrium constant, of increasing the temperature.

Which of these acids has the weakest conjugate base?

A.  $\mathrm{HCl}$

B.  ${\mathrm{CH}}_3\mathrm{COOH}$

C.  ${\mathrm{NH}}_4\mathrm{Cl}$

D.  ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$

Saturated aqueous hydrogen sulfide has a concentration of 0.10 mol dm⁻³ and a pH of 4.0. Demonstrate whether it is a strong or weak acid.

What is the strongest acid in the equation below?

H₃AsO₄ + H₂O $\rightleftharpoons$ H₂AsO₄⁻ + H₃O⁺      K_c = 4.5 × 10⁻⁴

A.  H₃AsO₄

B.  H₂O

C.  H₂AsO₄⁻

D.  H₃O⁺

20 cm³ of 1 mol dm⁻³ sulfuric acid was added dropwise to 20 cm³ of 1 mol dm⁻³ barium hydroxide producing a precipitate of barium sulfate.

H₂SO₄(aq) + Ba(OH)₂(aq) → 2H₂O (l) + BaSO₄(s)

Which graph represents a plot of conductivity against volume of acid added?

Suggest why the experiment should be carried out in a fume hood or in a well-ventilated laboratory.

State the equation for the reaction of NO₂ in the atmosphere to produce acid deposition.

Dissolved carbon dioxide causes unpolluted rain to have a pH of approximately 5, but other dissolved gases can result in a much lower pH. State one environmental effect of acid rain.

Formulate the equation for the reaction of nitrogen dioxide, NO₂, with water to form two acids.

Formulate the equation for the reaction of one of the acids produced in (e)(i) with calcium carbonate.

Dissolved carbon dioxide causes unpolluted rain to have a pH of approximately 5, but other dissolved gases can result in a much lower pH. State one environmental effect of acid rain.

What is the major reason why the pH of unpolluted rain is less than 7?

A. methane

B. carbon dioxide

C. nitrogen oxides

D. sulfur dioxide

What is the major reason why the pH of unpolluted rain is less than 7?

A. methane

B. carbon dioxide

C. nitrogen oxides

D. sulfur dioxide

Which of these oxides contribute to acid deposition?

I.  ${\mathrm{SO}}_2$
II.  ${\mathrm{NO}}_2$
III.  ${\mathrm{CO}}_2$

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

Outline how one calcium compound in the lime cycle can reduce a problem caused by acid deposition.

Outline how one calcium compound in the lime cycle can reduce a problem caused by acid deposition.

State the product formed from the reaction of SO₃ with water.