R2.3 How far? The extent of chemical change Questionbank

Practice R2.3 How far? The extent of chemical change with authentic IB Chemistry exam questions for both SL and HL students. This question bank mirrors Paper 1A, 1B, 2 structure, covering key topics like atomic structure, chemical reactions, and organic chemistry. Get instant solutions, detailed explanations, and build exam confidence with questions in the style of IB examiners.

Paper

Level

Question 1

HLPaper 2

The following infrared spectrum is for 2-butanone, an organic compound with the molecular formula $C_4H_8O$ .

Identify the functional group present in 2-butanone that corresponds to the strong absorption peak around 1715 $\text{cm}^{-1}$ .

[1]

Predict why there is no broad absorption peak in the region around 3200–3600 $\text{cm}^{-1}$ .

[2]

Discuss the significance of multiple sharp peaks appear between 1000-1300 $\text{cm}^{-1}$ in organic structure identification.

[2]

The IR spectrum of 2-butanone was recorded to monitor a chemical reaction.

Explain how this spectrum could be used to determine whether 2-butanol has been fully oxidized to 2-butanone.

[3]

2-butanone and butanoic acid have the same molecular formula.

Describe how their IR spectra would differ, and explain how these differences arise.

[3]

Question 2

HLPaper 2

The reaction:

$\mathrm{A(g)} + \mathrm{B(g)} \rightleftharpoons \mathrm{C(g)} + \mathrm{D(g)}$

was studied with the following initial concentrations:

$[\mathrm{A}] = 0.100\ \mathrm{mol\, dm^{-3}},\ [\mathrm{B}] = 0.100\ \mathrm{mol\, dm^{-3}},\ [\mathrm{C}] = 0.050\ \mathrm{mol\, dm^{-3}},\ [\mathrm{D}] = 0.050\ \mathrm{mol\, dm^{-3}}$

Write the expression for the reaction quotient $Q_c$ .

[1]

Calculate the value of $Q_c$ .

[1]

Given that $K_c = 4.00$ , predict the direction the reaction will proceed to reach equilibrium.

[2]

Question 3

HLPaper 2

Hydrogen peroxide decomposes in aqueous solution according to the reaction:

2H_2O_2(aq) \rightarrow 2H_2O(l)+O_2(g)

The concentration of hydrogen peroxide was measured over time. The graph below shows the concentration of H₂O₂ decreasing during the reaction.

Explain how the rate of reaction can be determined from the graph at a specific time.

[2]

Suggest why the curve flattens out as the reaction proceeds.

[1]

Calculate the average rate of reaction between $t = 0$ and $t = 60$ seconds, given that $[H_2O_2]$ falls from 0.400 mol dm^-3 to 0.200 mol dm^-3.

[2]

Describe how you would determine the initial rate of reaction using the graph.

[2]

The rate equation for the decomposition is:

$\text{Rate}=k[H_2O_2]^n$

Explain how you could determine the order of reaction, $n$ , from experimental data.

[3]

Sketch a graph of $\ln[\text{H}_2\text{O}_2]$ versus time for a first-order reaction.

[2]

Question 4

HLPaper 2

At $450\ \mathrm{K}$ , the equilibrium:

$\mathrm{N_2O_4(g)} \rightleftharpoons 2\mathrm{NO_2(g)}$

has $K_c = 0.133$ .

A student mixes: $[\mathrm{N_2O_4}] = 0.200\ \mathrm{mol\, dm^{-3}},\ [\mathrm{NO_2}] = 0.200\ \mathrm{mol\, dm^{-3}}$

Calculate $Q_c$ .

[2]

Predict the direction the equilibrium will shift.

[1]

Suggest the sign of $\Delta G^\circ$ and justify your answer.

[2]

Question 5

SLPaper 1A

What is the percentage yield when 7 g of ethene produces 6 g of ethanol?

$M_r$ (ethene) = 28 and $M_r$ (ethanol) = 46

$C_2H_4(g) + H_2O(g) → C_2H_5OH(g)$

Question 6

SLPaper 1A

Which factor does not affect the position of equilibrium in this reaction?

$2NO_2(g) \rightleftharpoons N_2O_4(g) \quad ΔH = −58 \, kJ mol^{−1}$

Question 7

SLPaper 1A

The equilibrium constant, $K_c$ , for the reaction $2A + 4B ⇌ 2C + 4D$ has a value of 4.0.

What is the value of $K_c$ for the reaction below at the same temperature?

$C + 2D ⇌ A + 2B$

Question 8

HLPaper 1A

Which is correct for a reaction with a positive change in Gibbs free energy, $ΔG^\ominus$ ?

Question 9

HLPaper 1A

Sulfur dioxide reacts with oxygen to form sulfur trioxide.

$2SO_2 (g) + O_2 (g) \rightleftharpoons 2SO_3 (g) \quad \quad \Delta H = −197 \, kJ$

Which change increases the value of $K_c$ ?

Question 10

SLPaper 1A

The equilibrium $2H_2 (g) + N_2 (g) ⇌ N_2H_4 (g)$ has an equilibrium constant, $K$ , at 150 °C.

What is the equilibrium constant at 150 °C, for the reverse reaction?

$N_2H_4 (g) ⇌ 2H_2 (g) + N_2 (g)$