The graph shows values of ΔG for a reaction at different temperatures.

Which statement is correct?

A.     The standard entropy change of the reaction is negative.

B.     The standard enthalpy change of the reaction is positive.

C.     At higher temperatures, the reaction becomes less spontaneous.

D.     The standard enthalpy change of the reaction is negative.

The graph shows Gibbs free energy of a mixture of N₂O₄(g) and NO₂(g) in different proportions.

N₂O₄(g) $\rightleftharpoons$ 2NO₂(g)

Which point shows the system at equilibrium?

Which energy profile diagram represents an exothermic S_N1 reaction?

Which technique is used to determine the bond lengths and bond angles of a molecule?

A.     X-ray crystallography

B.     Infrared (IR) spectroscopy

C.     Mass spectroscopy

D.     ¹H NMR spectroscopy

Which shows the first ionization energies of successive elements across period 2, from left to right?

Which technique involves breaking covalent bonds when carried out on an organic compound?

A. infrared spectroscopy

B. nuclear magnetic resonance spectroscopy

C. X-ray crystallography

D. mass spectrometry

Given equimolar concentrations, which substance would produce the strongest signal in a ¹H NMR spectrum?

A.  (CH₃)₃CH

B.  C₆H₆

C.  C₈H₁₈

D.  Si(CH₃)₄

What can be deduced from the infrared (IR) spectrum of a compound?

A. Number of hydrogens

B. Number of hydrogen environments

C. Bonds present

D. Molar mass

The following data were recorded for determining the density of three samples of silicon, Si.

Which average density value, in g cm⁻³, has been calculated to the correct number of significant figures?

A. 2

B. 2.3

C. 2.27

D. 2.273

The dotted line represents the formation of oxygen, O₂ (g), from the uncatalysed complete decomposition of hydrogen peroxide, H₂O₂ (aq).

Which curve represents a catalysed reaction under the same conditions?

The molar mass of a gas, determined experimentally, is 32 g mol⁻¹. Its literature molar mass is 40 g mol⁻¹.

What is the percentage error?

A.     80%

B.     25%

C.     20%

D.     8%

How should a measurement of 5.00 g from a balance be recorded?

A. 5.00 ± 0.1 g

B. 5.00 ± 0.01 g

C. 5.00 ± 1 g

D. 5.00 ± 0.001 g