NSAA 2022 Chemistry PART Y

• A.119
• B.120
• C.166
• D.200
• E.213
• F.248
• G.294
• H.342

Answer: D

The following diagram gives the mass spectra of samples of the elements gallium (Ga) and chlorine (Cl).

The mass spectrum for Gallium (Ga) shows two peaks: one at $m/z = 69$ with 60% abundance and one at $m/z = 71$ with 40% abundance. The mass spectrum for Chlorine (Cl) shows two peaks: one at $m/z = 35$ with 75% abundance and one at $m/z = 37$ with 25% abundance.

Gaseous gallium chloride has a formula of $GaCl_3$.

The mass spectrum of gallium chloride shows peaks at different mass-to-charge ratio ($m/z$ value).

What is the abundance ratio of the molecular ion $GaCl_3^+$ with the largest $m/z$ value to the smallest $m/z$ value?

• A.2:9
• B.2:16
• C.2:36
• D.2:54
• E.2:81

Answer: E

• A.$120^{\circ}$
• B.in the range $114^{\circ}-119^{\circ}$
• C.$109.5^{\circ}$
• D.in the range $104^{\circ}-109^{\circ}$
• E.$90^{\circ}$
• F.in the range $84^{\circ}-89^{\circ}$

Answer: F

• A.4:5
• B.5:4
• C.1:10
• D.10:1
• E.1:320
• F.320:1

Answer: A

When organic compounds are treated with an alkaline aqueous solution of iodine, a yellow precipitate is formed by those compounds that contain either of these structural fragments:

$H_3C-C(=O)-$ or $H_3C-CH(OH)-$

There are 8 structurally isomeric alcohols with the molecular formula $C_5H_{12}O$.

Each of these alcohols was heated under reflux with excess acidified potassium dichromate(VI).

How many of these alcohols gave a product that would form a yellow precipitate with an alkaline aqueous solution of iodine?

• A.1
• B.2
• C.3
• D.4
• E.5
• F.6
• G.7

Answer: B

• A.$1.8 \, cm^3$
• B.$2.7 \, cm^3$
• C.$3.6 \, cm^3$
• D.$5.4 \, cm^3$
• E.$18 \, cm^3$
• F.$27 \, cm^3$
• G.$36 \, cm^3$
• H.$54 \, cm^3$

Answer: D

$\Delta G$ (Gibbs free energy change), $\Delta H$ (enthalpy change) and $\Delta S$ (entropy change) are thermodynamic quantities for a reaction linked by the equation

$\Delta G = \Delta H - T\Delta S$

where T = temperature measured in kelvin (K).

The graph shows how $\Delta G$, in $kJ \, mol^{-1}$, varies with temperature, in K, for a reaction at constant pressure. The graph is a straight line with a negative gradient. The y-intercept (at T=0K) is approximately +150 $kJ \, mol^{-1}$. The x-intercept (where $\Delta G = 0$) is approximately 750 K.

Is the reaction endothermic or exothermic, and what is the value of $\Delta S$, in $J \, mol^{-1}K^{-1}$?

(Assume that $\Delta H$ and $\Delta S$ do not vary with temperature over this range.)

• A.the reaction is endothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is -0.20
• B.the reaction is endothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is +0.20
• C.the reaction is endothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is -200
• D.the reaction is endothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is +200
• E.the reaction is exothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is -0.20
• F.the reaction is exothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is +0.20
• G.the reaction is exothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is -200
• H.the reaction is exothermic, $\Delta S / J \, mol^{-1}K^{-1}$ is +200

Answer: G

• A.$+650 \, kJ \, mol^{-1}$
• B.$-430 \, kJ \, mol^{-1}$
• C.$-790 \, kJ \, mol^{-1}$
• D.$-910 \, kJ \, mol^{-1}$
• E.$-980 \, kJ \, mol^{-1}$
• F.$-1270 \, kJ \, mol^{-1}$
• G.$-1380 \, kJ \, mol^{-1}$
• H.$-1700 \, kJ \, mol^{-1}$

Answer: C

• A.Copper(II) ions are a stronger reducing agent than iron(II) ions.
• B.Copper(II) ions are a stronger oxidising agent than iron(III) ions.
• C.Iron(II) ions are a stronger reducing agent than copper metal.
• D.Copper metal is a stronger oxidising agent than iron(II) ions.
• E.Iron(III) ions are a stronger oxidising agent than copper(II) ions.

Answer: E

• A.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{ethanol})} \times M_r^{(\text{propanol})} \times m^{(\text{ethanol})}}{\Delta T^{(\text{propanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{propanol})}}$
• B.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{ethanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{ethanol})}}{\Delta T^{(\text{propanol})} \times M_r^{(\text{propanol})} \times m^{(\text{propanol})}}$
• C.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{ethanol})} \times M_r^{(\text{propanol})} \times m^{(\text{propanol})}}{\Delta T^{(\text{propanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{ethanol})}}$
• D.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{propanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{ethanol})}}{\Delta T^{(\text{ethanol})} \times M_r^{(\text{propanol})} \times m^{(\text{propanol})}}$
• E.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{propanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{propanol})}}{\Delta T^{(\text{ethanol})} \times M_r^{(\text{propanol})} \times m^{(\text{ethanol})}}$
• F.$\Delta H^{(\text{ethanol})} \times \frac{\Delta T^{(\text{propanol})} \times M_r^{(\text{propanol})} \times m^{(\text{ethanol})}}{\Delta T^{(\text{ethanol})} \times M_r^{(\text{ethanol})} \times m^{(\text{propanol})}}$

Answer: F

• A.If hydrogen is detected in $t$ minutes, then helium will be detected in $\sqrt{2}t$ minutes.
• B.The kinetic energy of every gas particle in the box will be the same at the same room temperature.
• C.The order in which the gases are detected at both temperatures is hydrogen, then helium, then nitrogen, and lastly neon.
• D.The average speed at which a helium particle travels is 5 times the speed at which an average neon particle travels.
• E.When the temperature of the box is increased, the average kinetic energy of the gases will decrease.

Answer: A

A high temperature reaction vessel requires a steady supply of an atmosphere free of oxygen, carbon monoxide and $NO_x$ gases.

In order to achieve this, methane was burned in air to give a mixture of carbon dioxide, water vapour and nitrogen only.

A diagram shows 'methane + air' entering a 'burner', which outputs into a 'reactor vessel', with an 'exhaust' leaving the reactor vessel.

Assume that air is composed of 20% oxygen and 80% nitrogen only by volume.

What mass ratio of air to methane should be supplied to the burner?

($A_r$ values: H = 1; C = 12; N = 14; O = 16. Assume that one mole of any gas occupies the same volume at a given temperature and pressure.)

• A.2:1
• B.2.5:1
• C.4.5:1
• D.5:1
• E.9:1
• F.18:1
• G.20:1

Answer: F

• A.2.9
• B.3.4
• C.3.6
• D.4.4
• E.4.6
• F.5.4
• G.6.0
• H.7.0

Answer: B

• A.5.42 g
• B.5.78 g
• C.6.38 g
• D.6.56 g
• E.9.26 g
• F.9.62 g
• G.12.76 g
• H.13.12 g

Answer: D

Sodium feredetate trihydrate and iron(II) sulfate can both be used to treat iron deficiency.

The formula for sodium feredetate trihydrate is shown in a diagram as a complex of $Fe^{3+}$ and $Na^{+}$ with an EDTA-like ligand, along with three water molecules ($•3H_2O$).

Sodium feredetate trihydrate is used as a solution. $5.00 \, cm^3$ of this solution contains 210.5 mg of sodium feredetate trihydrate.

Iron(II) sulfate is used in tablet form. One iron tablet contains 63.0 mg of iron(II) ions.

What volume of sodium feredetate trihydrate solution would give the same mass of iron as one iron(II) sulfate tablet?

($A_r$ values: H = 1.0; C = 12; N = 14; O = 16; Na = 23; Fe = 56)

• A.$0.450 \, cm^3$
• B.$2.25 \, cm^3$
• C.$9.81 \, cm^3$
• D.$10.29 \, cm^3$
• E.$10.93 \, cm^3$
• F.$11.25 \, cm^3$

Answer: F

• A.$6.25 \, cm^3$
• B.$9.38 \, cm^3$
• C.$12.50 \, cm^3$
• D.$25.00 \, cm^3$
• E.$37.50 \, cm^3$
• F.$56.25 \, cm^3$
• G.$112.50 \, cm^3$

Answer: D

• A.1-bromobutane
• B.1-bromopentane
• C.1-bromopropane
• D.2-bromo-2-methylpropane
• E.2-bromobutane
• F.2-bromo-2-methylbutane
• G.2-bromopropane
• H.3-bromopentane

Answer: E

• A.$0.02 \, mol \, dm^{-3}$
• B.$0.04 \, mol \, dm^{-3}$
• C.$0.10 \, mol \, dm^{-3}$
• D.$0.20 \, mol \, dm^{-3}$
• E.$0.50 \, mol \, dm^{-3}$
• F.$1.00 \, mol \, dm^{-3}$

Answer: A

• A.10%
• B.20%
• C.30%
• D.40%
• E.50%
• F.60%
• G.70%
• H.80%

Answer: B

• A.6.30 kg of sodium fluoride (NaF)
• B.7200 g of hexafluorosilicic acid ($H_2SiF_6$)
• C.14400 g of hexafluorosilicic acid ($H_2SiF_6$)
• D.18.8 g of sodium fluorosilicate ($Na_2SiF_6$)
• E.37.6 kg of sodium fluorosilicate ($Na_2SiF_6$)

Answer: B