Syllabus Edition

First teaching 2014

Last exams 2024

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Theories & Reactions of Acids & Bases (DP IB Chemistry: SL)

Exam Questions

2 hours43 questions
1a1 mark

Define a Brønsted–Lowry acid.

1b1 mark

Which species in the following reaction acts as a Brønsted-Lowry base.

HSO4- (aq) + H3O+ (aq) rightwards harpoon over leftwards harpoon H2SO4 (aq) + H2O (l)]

1c1 mark

Which species in the following equation is acting as a Brønsted-Lowry acid.

CO32- (aq) + H+ (aq) rightwards harpoon over leftwards harpoonHCO3- (aq)

1d2 marks

Explain, using the Brønsted-Lowry theory, how water can act either as an acid or a base.

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2a1 mark

Describe the difference between an amphiprotic and amphoteric species.

2b2 marks

Write an equation to show ammonia, NH3, acting as both a Brønsted–Lowry base and a Brønsted–Lowry acid.

   Brønsted–Lowry base: ....................

   Brønsted–Lowry acid:  ....................

2c1 mark

The equations for two acid-base reactions are given below.

HCO3 (aq) + H2O (l)  H2CO3 (aq) + OH (aq)
HCO3 (aq) + H2O (l) not stretchy rightwards harpoon over leftwards harpoon CO32– (aq) + H3O+ (aq)

Identify two different amphiprotic species in the above reactions.

2d2 marks

i)        State what is meant by the term conjugate base.

[1]

ii)       State the conjugate base of the hydroxide ion, OH– 

[1]

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3a1 mark

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

3b1 mark

State an equation for the reaction of lithium oxide with dilute nitric acid.

3c2 marks

Which acid and base would be required to produce ammonium sulfate, (NH4)2SO4

3d3 marks

Nitric acid and calcium hydroxide react together.

i)        State the type of reaction that takes place.

[1]

ii)       State the formula of the products of the reaction.

[1]

iii)      State the sign of the enthalpy change for this reaction.

[1]

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4a1 mark

Identify one conjugate acid-base pair in the reaction.

OCl(aq) + H2O (l) rightwards harpoon over leftwards harpoon OH(aq) + HOCl (aq)
4b1 mark

State an equation for the reaction of aluminium hydroxide with dilute sulfuric acid.

4c1 mark

State an equation for the reaction of calcium hydrogencarbonate with dilute phosphoric acid, H3PO4.

4d3 marks

Write the formulae for the following:

i)   Carbonic acid.  [1]

ii)   Ammonium sulfate.  [1]

iii)   Magnesium ethanoate.  [1]

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1a1 mark

Malonic acid is a naturally occurring acid found in fruits and vegetables and is shown in Figure 1.

Figure 1 

q1a-figure-1

The first dissociation of malonic acid is:

C3H4O4 (aq) + H2O (l) C3H3O4- (aq) + H3O+ (aq)

Identify one conjugate acid-base pair from the equation.

1b3 marks

The equilibrium constant for the first dissociation of malonic acid is 1.48 x 10-3.

State, with a reason, the strength of malonic acid.

1c1 mark

The anion C3H3O4- may be classified as amphiprotic. Explain the meaning of amphiprotic and write equations, using C3H3O4-, to illustrate your answer.

1d1 mark

Under the right conditions, malonic acid can react with ethanol to form diethyl malonate, a diester.

Draw a displayed formula for diethyl malonate showing all the bonds.

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2a1 mark

Salicylic acid has the structure shown below in Figure 1.                             

Figure 1

q2a-figure-1

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

2b2 marks

Predict what would be seen if a small amount of copper (II) oxide was added to an aqueous solution of salicylic acid, HOC6H4COOH, and warmed.

Write a balanced equation for the reaction.

2c1 mark

Suggest, with a reason, whether salicylic acid is likely to be soluble in water.

2d1 mark

Determine the relative molecular mass, Mr, of salicylic acid using Table 6 from the Data book.

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3a3 marks

Write balanced equations to show the separate reactions between ethanoic acid and calcium carbonate, CaCO3, magnesium oxide, MgO, and aluminium hydroxide, Al(OH)3.

3b2 marks

In Table 1 below, suggest the names and formulae of the acids and bases needed to make the specified salts.

Table 1

Acid

Base

Salt

 

 

Copper nitrate, Cu(NO3)2

 

 

Calcium phosphate, Ca3(PO4)2

3c3 marks

The ethanoate ion, CH3COO-, carbon dioxide, CO2, and the ethoxide ion, CH3CH2O-, all contain carbon oxygen bonds. 

Deduce the order in carbon to oxygen bond length from shortest to longest and explain your answer.

3d2 marks

Ethanoic acid, CH3COOH, shows two absorptions in an infrared spectrum that are not present in the spectrum of ethanol.

Using Table 26 of the Data book, state the wavenumber range of these absorptions and the bonds that cause them.

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4a2 marks

Glycolic acid, C2H4O3, is a colourless, odourless crystalline solid that is highly soluble in water and behaves as a Brønsted–Lowry acid.

i)

Define the term Brønsted–Lowry acid.

ii)

State one difference between Brønsted–Lowry acids and the traditional theory of acids as substances that dissociate in water to form hydrogen ions.

4b1 mark

The systematic IUPAC name for glycolic acid is 2-hydoxyethanoic acid.

Draw the structural formula for its conjugate base, showing all the atoms and bonds.

4c2 marks

Write an equation for the reaction between glycolic acid, C2H4O3, and limescale, CaCO3. State and explain one observation you would make.

4d1 mark

State one reason why you would use glycolic acid to remove the limescale in a kettle at home, but not hydrochloric acid.

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5a2 marks

An alkaline solution is formed when sodium hydrogencarbonate is dissolved in water.

Write an equation for the reaction and explain why the solution is alkaline.

5b2 marks

 State whether the HCO3- ion is behaving as a Brønsted–Lowry acid or as a base and give a reason for your answer.

5c1 mark

Carbon dioxide gas dissolves in rainwater to form carbonic acid. State the formula of the conjugate base of carbonic acid.

5d1 mark

Carbonic acid and sulfuric acid can be described as diprotic acids. Explain the meaning of diprotic.

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1a2 marks

Explain why an ammonium ion can not behave as a Brønsted-Lowry base.

1b2 marks

State and explain the acid-base character of aqueous ammonia at 298 K.

1c2 marks

Acids can be classed as monoprotic, diprotic and triprotic. Sulfuric acid is a diprotic acid. 

i)
State the equation for the first ionisation step of sulfuric acid, including state symbols.

ii)
Label the conjugate acid and base pairs in your answer to part i).
1d1 mark

The second ionisation step is for the ionisation of sulfuric acid is as follows.

HSO4- (aq) + H2O (aq) ⇌ SO42- (aq) + H3O+ (aq)

Suggest why the second ionisation step reaches equilibrium.

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2a2 marks

Sodium hydrogen carbonate solution, NaHCO3 (aq) , can act as an amphiprotic species. State the equation for the reaction fo NaHCO3 (aq) with the following compounds:

i)
Sodium hydroxide solution. 
[1]
ii)
Hydrochloric acid. 
[1]

2b3 marks

Using your answer to part a) i) and ii), explain why NaHCOis amphiprotic. 

2c3 marks

Phosphine is usually prepared by heating white phosphorus, one of the allotropes of phosphorus, with concentrated aqueous sodium hydroxide.

The equation for the reaction is.

P4 (s) + 3OH (aq) + 3H2O (l) → PH3 (g) + 3H2PO2 (aq)

Identify the amphiprotic species in this reaction giving the formulas of both species it is converted to when it behaves in this manner.

2d4 marks

1.68 g of white phosphorus was used to make phosphine

i)
Calculate the amount, in mol, of white phosphorus used.
[1]
ii)
This phosphorus was reacted with 50.0 cm3 of 3.00 mol dm−3 aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent.
[1]
iii)
Determine the excess amount, in mol, of the other reagent.
[1]
iv)
Using section 2 of the data booklet. Determine the volume of phosphine, measured in cm3 at standard temperature and pressure, that was produced.
[1]

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3a2 marks

Oxalic acid, H2C2O, is a weak diprotic acid and can be used in titrations. State the equation for the reaction of oxalic acid with sodium hydroxide. 

3b2 marks

The ionisation of oxalic acid occurs in two steps. State equations for both of these steps. 

3c3 marks

Tartaric acid shown below behaves as a Brønsted-Lowry acid when it reacts with calcium hydroxide, Ca(OH)2. Sketch the structure of the salt formed from this reaction. 

8-1-ib-sl-sq-hard-q3c-tartaric-acid

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4a4 marks

Using ionic equations state how HPO42- can behave as an amphiprotic and amphoteric species.

4b2 marks

Gallium oxide behaves as an amphoteric oxide. State two equations to show how gallium oxide reacts with a strong monoprotic acid and strong base.

Reaction with strong monoprotic acid .........................................................................................................................................

Reaction with strong base .........................................................................................................................................

4c1 mark

Identify the Br∅nsted-Lowry acids in the following reaction.

CH3CH2O- (aq) + H2O (l) rightwards harpoon over leftwards harpoonCH3CH2OH (aq) + OH- (aq)

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