Practice gce model questions vol1 chemistry 2017 Past Questions

Question 1 View Details

A buffer solution is prepared by dissolving 0.20 mol of acetic acid (CH₃COOH) and 0.15 mol of sodium acetate (CH₃COONa) in enough water to make 1.00 L of solution. After the buffer is prepared, 0.05 mol of hydrochloric acid (HCl) is added. Assuming the volume change is negligible, calculate the pH of the solution after the addition of HCl. (Ka of acetic acid = 1.8 \times 10⁻⁵).

Correct A. 4.35

B. 4.70

C. 5.00

D. 4.10

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 2 View Details

5.0 g of sodium chloride (NaCl) is dissolved in 150 g of water at 25 °C. Given that the molal boiling point elevation constant (K_b) of water is 0.512 °C·kg mol⁻¹ and that NaCl dissociates completely into two ions in solution, calculate the boiling point of the resulting solution. Give your answer to two decimal places.

A. 99.85

B. 100.12

Correct C. 100.58

D. 101.03

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 3 View Details

2.00 g of magnesium metal reacts with excess hydrochloric acid according to the equation: Mg + 2 HCl → MgCl₂ + H₂. The hydrogen gas produced is collected at STP and the measured volume is 0.45 L. Calculate the percent yield of hydrogen gas based on the mass of magnesium used. Give your answer to one decimal place.

Correct A. 24.4

B. 36.6

C. 48.8

D. 12.2

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 4 View Details

In an acidic solution, potassium permanganate (KMnO₄) reacts with excess ferrous ions (Fe²⁺) according to the balanced equation: MnO₄⁻ + 5 Fe²⁺ + 8 H⁺ → Mn²⁺ + 5 Fe³⁺ + 4 H₂O. If 10.0 g of KMnO₄ is used, calculate the mass of Fe³⁺ ions formed. (Atomic masses: K = 39.10, Mn = 54.94, O = 16.00, Fe = 55.85, H = 1.01). Give your answer to three significant figures.

A. 25.0

B. 14.2

C. 21.5

Correct D. 17.7

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 5 View Details

A galvanic cell is constructed as follows: Zn|Zn²⁺ (0.010 M) || Cu²⁺ (0.10 M)|Cu. The standard electrode potentials are E°(Zn²⁺/Zn) = -0.76 V and E°(Cu²⁺/Cu) = +0.34 V. Calculate the cell potential at 25 °C. (Use the Nernst equation with 0.0592 V for (RT/F)·log₁₀ at 25 °C.) Give your answer to two decimal places.

A. 1.05

Correct B. 1.13

C. 0.86

D. 1.20

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 6 View Details

A \(25.0\ \text{mL}\) sample of a weak monoprotic acid HA is titrated with \(0.100\ \text{M}\) NaOH. At the half‑equivalence point the measured pH is \(4.75\). After adding \(12.5\ \text{mL}\) of NaOH the pH is \(9.20\). Determine (a) the acid dissociation constant \(K_a\) of HA and (b) the initial concentration of HA in the sample.

A. K_a = 1.78×10⁻⁵; initial concentration = 0.0600 M

B. K_a = 2.10×10⁻⁵; initial concentration = 0.0450 M

Correct C. K_a = 1.78×10⁻⁵; initial concentration = 0.0500 M

D. K_a = 1.78×10⁻⁴; initial concentration = 0.0500 M

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 7 View Details

A \(100.0\ \text{mL}\) solution of \(0.0100\ \text{M}\) Na₂SO₄ is mixed with \(50.0\ \text{mL}\) of \(0.0200\ \text{M}\) BaCl₂ at \(25\ °C\). BaSO₄ has \(K_{sp}=1.1\times10^{-10}\). (a) Calculate the mass of BaSO₄ that precipitates. (b) The mixture is then heated to \(35\ °C\) where \(K_{sp}=2.5\times10^{-10}\); determine the additional mass of BaSO₄ that will dissolve.

A. 0.200 g precipitated; 1.5×10⁻⁴ g dissolves on heating

B. 0.233 g precipitated; 2.5×10⁻⁴ g dissolves on heating

Correct C. 0.233 g precipitated; 1.9×10⁻⁴ g dissolves on heating

D. 0.250 g precipitated; 2.0×10⁻⁴ g dissolves on heating

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 8 View Details

The coordination complex \([\text{Ni(CN)}_{4}]^{2-}\) is square planar, shows a magnetic moment of 0 BM and exhibits an absorption maximum at \(500\ \text{nm}\). (a) Determine the oxidation state of Ni and its d‑electron count. (b) Estimate the crystal‑field splitting energy (Δ) in kJ mol\(^{-1}\) from the absorption data.

A. Ni oxidation state +2; d‑electron count 9; Δ ≈ 240 kJ mol⁻¹

B. Ni oxidation state +1; d‑electron count 9; Δ ≈ 210 kJ mol⁻¹

C. Ni oxidation state +3; d‑electron count 7; Δ ≈ 260 kJ mol⁻¹

Correct D. Ni oxidation state +2; d‑electron count 8; Δ ≈ 240 kJ mol⁻¹

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 9 View Details

Among the elements Na, Mg, Al and Si, which has the highest first ionisation energy?

A. Mg

Correct B. Si

C. Na

D. Al

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 10 View Details

A hydrocarbon with formula C₅H₁₀ combusts completely in excess O₂, releasing \(-3260\) kJ mol\(^{-1}\). Its standard enthalpies of formation are \(\Delta_f H^\circ(\text{CO}_2) = -393.5\) kJ mol\(^{-1}\) and \(\Delta_f H^\circ(\text{H}_2\text{O},\ell) = -285.8\) kJ mol\(^{-1}\). (a) Calculate the standard enthalpy of formation of the hydrocarbon. (b) When the same hydrocarbon is hydrogenated under standard conditions, the enthalpy change is \(-30\) kJ mol\(^{-1}\). Based on this information, decide whether the hydrocarbon is an alkene or a cycloalkane.

Correct A. Δ_fH° ≈ -137 kJ mol⁻¹; the hydrocarbon is a cycloalkane

B. Δ_fH° ≈ -200 kJ mol⁻¹; the hydrocarbon is a cycloalkane

C. Δ_fH° ≈ -120 kJ mol⁻¹; the hydrocarbon is an alkene

D. Δ_fH° ≈ -150 kJ mol⁻¹; the hydrocarbon is an alkene

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 11 View Details

Element X has an electronegativity of 2.1 and element Y has an electronegativity of 3.5. When they combine to form a binary compound XY, determine the type of chemical bond (ionic, polar covalent, or non‑polar covalent) and state whether the compound is expected to be soluble in water.

A. non‑polar covalent, insoluble

B. ionic, soluble

C. ionic, insoluble

Correct D. polar covalent, soluble

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 12 View Details

Aluminium reacts with chlorine gas according to \(2 \text{Al} + 3 \text{Cl}_2 \rightarrow 2 \text{AlCl}_3\). If 5.0 g of Al and 10.0 g of Cl\(_2\) are mixed and the reaction proceeds with an 85 % yield, calculate the mass of aluminium chloride actually obtained.

A. 12.3 g

B. 9.2 g

C. 8.5 g

Correct D. 10.7 g

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 13 View Details

Chlorine gas reacts with fluorine gas to give chlorine monofluoride according to \(\text{Cl}_2 + \text{F}_2 \rightarrow 2 \text{ClF}\). The bond dissociation energies are: \(D(\text{Cl-Cl}) = 242\ \text{kJ mol}^{-1}\), \(D(\text{F-F}) = 158\ \text{kJ mol}^{-1}\), \(D(\text{Cl-F}) = 255\ \text{kJ mol}^{-1}\). If 50.0 g of \(\text{Cl}_2\) is allowed to react with excess \(\text{F}_2\), (a) calculate the mass of \(\text{ClF}\) formed, and (b) determine the overall enthalpy change for the process.

A. 73.5 g, +85 kJ

B. 80.2 g, -45 kJ

C. 68.0 g, +110 kJ

Correct D. 76.8 g, +78 kJ

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 14 View Details

A lake of volume \(1.0 \times 10^{6}\ \text{L}\) contains lead(II) ions at an initial concentration of \(0.05\ \text{mg L}^{-1}\). Sodium sulfide is added, establishing a sulfide ion concentration of \(1.0 \times 10^{-3}\ \text{M}\). Given the solubility product \(K_{sp}(\text{PbS}) = 8 \times 10^{-28}\), (a) calculate the equilibrium concentration of \(\text{Pb}^{2+}\) after treatment, and (b) determine the mass of lead removed from the lake.

A. [Pb2+] = 5×10⁻²⁴ M, mass removed ≈ 25 g

B. [Pb2+] = 2×10⁻⁶ M, mass removed ≈ 5 g

Correct C. [Pb2+] = 8×10⁻²⁵ M, mass removed ≈ 50 g

D. [Pb2+] = 1×10⁻²⁰ M, mass removed ≈ 0.5 g

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 15 View Details

The phase diagram of substance X shows that at a pressure of 1 atm the boiling point is 350 K. At this point the slope of the liquid-vapour equilibrium line is \(dP/dT = 0.12\ \text{atm K}^{-1}\). Using the Clapeyron approximation \(\Delta H_{vap} = \Delta V\, dP/dT\, T\) and assuming the molar volume of the liquid is negligible compared with that of the vapour (ideal‑gas behaviour), calculate the molar enthalpy of vaporisation \(\Delta H_{vap}\) in kJ mol⁻¹.

A. 135 kJ mol⁻¹

Correct B. 122 kJ mol⁻¹

C. 150 kJ mol⁻¹

D. 115 kJ mol⁻¹

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 16 View Details

A sample containing 10.0 g of aluminium metal is mixed with 20.0 g of copper(II) chloride solution. During the reaction, 10 % of the aluminium is consumed by a side‑reaction with water to form aluminium hydroxide and does not participate in the main displacement reaction: (2\,\text{Al} + 3\,\text{CuCl}_2 \rightarrow 2\,\text{AlCl}_3 + 3\,\text{Cu}\). The main reaction proceeds with an 85 % isolated yield of copper. Calculate the mass of copper actually obtained (in grams, to three significant figures).

A. 9.45 g

B. 7.20 g

Correct C. 8.04 g

D. 8.70 g

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 17 View Details

Consider the galvanic cell: Zn(s) | Zn^{2+} (0.010 M) || Cu^{2+} (0.50 M) | Cu(s) at 298 K. Standard reduction potentials are \(E^{\circ}(\text{Cu}^{2+}/\text{Cu})=+0.34\text{ V}\) and \(E^{\circ}(\text{Zn}^{2+}/\text{Zn})=-0.76\text{ V}\). (a) Calculate the cell emf under the given conditions using the Nernst equation. (b) If 0.025 mol of electrons pass through the cell, how many grams of copper are deposited on the cathode? (Give your answer to three significant figures.)

Correct A. E = 1.15 V; mass of Cu = 0.794 g

B. E = 1.10 V; mass of Cu = 0.750 g

C. E = 1.05 V; mass of Cu = 0.700 g

D. E = 1.20 V; mass of Cu = 0.820 g

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 18 View Details

Metals A, B and C are aluminium (Al), zinc (Zn) and iron (Fe) respectively. Their standard reduction potentials are: Al^{3+}+3e^- \rightarrow Al E^{\circ}=-1.66\text{ V} Zn^{2+}+2e^- \rightarrow Zn E^{\circ}=-0.76\text{ V} Fe^{2+}+2e^- \rightarrow Fe E^{\circ}=-0.44\text{ V} (a) Rank the metals in order of decreasing reactivity towards dilute hydrochloric acid. (b) Using the standard enthalpies of formation (kJ mol^{-1}): \(\Delta_fH^{\circ}(\text{Al}_2\text{O}_3)=-1675\), \(\Delta_fH^{\circ}(\text{ZnO})=-350\), \(\Delta_fH^{\circ}(\text{Fe}_2\text{O}_3)=-824\), determine which metal forms the most thermodynamically stable oxide. (c) Calculate the enthalpy change for the reaction \(2\text{Al}+3\text{Cl}_2\rightarrow2\text{AlCl}_3\), given \(\Delta_fH^{\circ}(\text{AlCl}_3)=-704\text{ kJ mol}^{-1}\).

Correct A. (a) Al > Zn > Fe; (b) Aluminium; (c) -1408 kJ

B. (a) Zn > Al > Fe; (b) Iron; (c) -1408 kJ

C. (a) Al > Fe > Zn; (b) Zinc; (c) -1408 kJ

D. (a) Al > Zn > Fe; (b) Aluminium; (c) -1500 kJ

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 19 View Details

A 2.00 L container at 298 K holds a mixture of oxygen and nitrogen gases at a total pressure of 1.20 atm. The total mass of the gas mixture is 2.80 g. Assuming ideal behaviour, calculate the mass of oxygen present in the mixture (to three significant figures).

A. 0.470 g

Correct B. 0.411 g

C. 0.350 g

D. 0.511 g

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 20 View Details

Write the ground‑state electron configuration of copper (atomic number 29). Using this configuration, state how many electrons are present in the \(n=3\) shell.

A. [Ar] 3d^{9} 4s^{2}; 18 electrons in n=3

Correct B. [Ar] 3d^{10} 4s^{1}; 18 electrons in n=3

C. [Ar] 3d^{10} 4s^{1}; 20 electrons in n=3

D. [Ar] 3d^{10} 4s^{2}; 18 electrons in n=3

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 21 View Details

When 2‑methyl‑1,3‑butanediol is heated with concentrated (\mathrm{H_2SO_4}\), it can undergo dehydration. Considering all possible distinct products—including alkenes formed by elimination and the cyclic ether formed by intramolecular dehydration—how many different products can be obtained?

Correct A. 4

B. 6

C. 3

D. 5

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 22 View Details

An unknown element has a most abundant isotope with mass number 35 and atomic number 17. How many neutrons are present in this isotope?

A. 20

B. 17

C. 19

Correct D. 18

Correct Answer: D

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 23 View Details

A 2.00 g mixture of ethanol (\(\mathrm{C_2H_5OH}\), \(M = 46.07\ \mathrm{g\,mol^{-1}}\)) and isopropanol (\(\mathrm{C_3H_7OH}\), \(M = 60.10\ \mathrm{g\,mol^{-1}}\)) reacts with excess sodium metal. The reaction produces \(0.45\ \mathrm{L}\) of hydrogen gas at STP. If the mass of ethanol is twice that of isopropanol, calculate the mass percent of ethanol in the original mixture.

A. 33.3

B. 55.6

Correct C. 66.7

D. 75.0

Correct Answer: C

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 24 View Details

A \(5.00\ \mathrm{g}\) sample of calcium carbonate (\(\mathrm{CaCO_3}\), \(M = 100.09\ \mathrm{g\,mol^{-1}}\)) is reacted with excess hydrochloric acid according to \(\mathrm{CaCO_3 + 2\,HCl \rightarrow CaCl_2 + CO_2 + H_2O}\). The carbon dioxide gas is collected over water at \(25^{\circ}\mathrm{C}\) and a total pressure of \(750\ \mathrm{mmHg}\). The water vapour pressure at this temperature is \(23\ \mathrm{mmHg}\). The volume of dry \(\mathrm{CO_2}\) collected is \(1.20\ \mathrm{L}\). Determine the percent yield of \(\mathrm{CO_2}\).

Correct A. 94

B. 78

C. 85

D. 100

Correct Answer: A

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

Question 25 View Details

Benzoic acid (\(\mathrm{C_6H_5COOH}\), \(M = 122.12\ \mathrm{g\,mol^{-1}}\)) is dissolved in water to give \(0.250\ \mathrm{mol}\) of acid. Sodium hydroxide solution of concentration \(0.200\ \mathrm{mol\,L^{-1}}\) is added dropwise until the pH reaches 5.0. Given the acid dissociation constant \(K_a = 6.3 \times 10^{-5}\), calculate the volume of NaOH solution required (in millilitres).

A. 1150

Correct B. 1080

C. 950

D. 1020

Correct Answer: B

Want to see the full step-by-step solution? Unlock AI Explanation & Analytics

gce model questions vol1 2017 chemistry | Objective

Master the Exam!

Help others prepare! Share this practice hub: