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POST UTME LASU 2019 Chemistry | Objective

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Question 1

Determine the s\tandard Gibbs free energy change (ΔG°) for the reaction: 2Ag+(aq) + 2Cl-(aq) → 2AgCl(s) at 25°C and 1 atm.

A. -120 kJ/mol

Correct B. -240 kJ/mol

C. -60 kJ/mol

D. -300 kJ/mol

Correct Answer: B

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Question 2

A 0.1 M solution of HCl is titrated with 0.1 M NaOH. At the equivalence point, the pH of the solution is 7. Determine the initial volume of HCl (in mL) required to reach the equivalence point.

A. 10 mL

Correct B. 20 mL

C. 30 mL

D. 40 mL

Correct Answer: B

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Question 3

A diagram of a simple electrolytic cell is shown below. If the cell is operated at a cons\tant current of 2 A for 5 minutes, what is the mass of copper deposited at the cathode?

Correct A. 0.12 g

B. 0.24 g

C. 0.36 g

D. 0.48 g

Correct Answer: A

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Question 4

A 2.0 M solution of H2SO4 is mixed with 2.0 M NaOH. Determine the pH of the resulting solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 5

A diagram of a simple distillation apparatus is shown below. If the apparatus is operated at a cons\tant temperature of 100°C, what is the vapor pressure of the liquid at equilibrium?

Correct A. 101.3 kPa

B. 101.5 kPa

C. 101.7 kPa

D. 101.9 kPa

Correct Answer: A

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Question 6

The electronegativity of an element in a compound is a measure of its ability to attract electrons towards itself. Which of the following elements has the highest electronegativity among the given options?

Correct A. Fluorine (F)

B. Chlorine (Cl)

C. Bromine (Br)

D. Iodine (I)

Correct Answer: A

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Question 7

A sample of a gas at 25°C and 1 atm is allowed to expand to twice its original volume. What is the new pressure of the gas, assuming ideal gas behavior?

A. 0.5 atm

B. 1 atm

Correct C. 2 atm

D. 4 atm

Correct Answer: C

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Question 8

The reaction between sodium (Na) and chlorine (Cl2) to form sodium chloride (NaCl) is an example of a redox reaction. What is the oxidation state of sodium in NaCl?

Correct A. +1

B. -1

C. 0

D. +2

Correct Answer: A

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Question 9

A 2.5 L sample of a gas at 27°C is collected over water at 25°C. The total pressure of the gas is 755 mmHg. What is the partial pressure of the gas?

A. 600 mmHg

B. 700 mmHg

Correct C. 750 mmHg

D. 800 mmHg

Correct Answer: C

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Question 10

The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of combustion of 1 mole of CO?

A. -110.5 kJ/mol

Correct B. -111.5 kJ/mol

C. -112.5 kJ/mol

D. -113.5 kJ/mol

Correct Answer: B

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Question 11

A sample of an ideal gas at 25°C and 1 atm is heated to 100°C at cons\tant pressure. What is the ratio of the final volume to the initial volume?

A. 1:1

B. 1:2

Correct C. 2:1

D. 3:1

Correct Answer: C

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Question 12

A solution of CuSO4 is electrolyzed u\sing a platinum electrode. What is the product at the anode?

A. O2

Correct B. Cu

C. SO2

D. H2O

Correct Answer: B

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Question 13

The atomic number of an element is 12. What is the number of protons in the nucleus of an atom of this element?

A. 10

Correct B. 12

C. 14

D. 16

Correct Answer: B

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Question 14

A metal alloy is made by mixing 30% Cu, 20% Zn, and 50% Sn. What is the percentage of Cu in the alloy?

Correct A. 15%

B. 20%

C. 25%

D. 30%

Correct Answer: A

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Question 15

A solution of HCl is electrolyzed u\sing a platinum electrode. What is the product at the cathode?

Correct A. H2

B. Cl2

C. H2O

D. NaCl

Correct Answer: A

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Question 16

The rate cons\tant (k) of a first-order reaction is given by the equation: k = Ae^\( -Ea/RT \). If the activation energy (Ea) is 50 kJ/mol, the gas cons\tant (R) is 8.314 J/mol*K, and the temperature (T) is 300 K, what is the value of the rate cons\tant (k) if the pre-exponential factor (A) is 1.0 x 10^10 s^-1?

A. 1.0 x 10^5 s^-1

B. 1.0 x 10^6 s^-1

Correct C. 1.0 x 10^7 s^-1

D. 1.0 x 10^8 s^-1

Correct Answer: C

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Question 17

A solution contains 0.1 M NaCl. If 10 mL of this solution is diluted to 100 mL, what is the concentration of the resulting solution?

Correct A. 0.01 M

B. 0.1 M

C. 1.0 M

D. 10 M

Correct Answer: A

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Question 18

A metal (M) reacts with oxygen to form a metal oxide (MO). The balanced equation for the reaction is: 4M + 3O2 → 2MO. If 2.0 g of M is reacted with 1.0 L of O2 at STP, what is the limiting reac\tant?

A. M

Correct B. O2

C. MO

D. Neither M nor O2 is the limiting reac\tant

Correct Answer: B

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Question 19

A polymer (P) has a molecular weight of 100,000 g/mol. If 1.0 g of P is dissolved in 100 mL of solvent, what is the concentration of the solution?

Correct A. 1.0 M

B. 10 M

C. 100 M

D. 1000 M

Correct Answer: A

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Question 20

A solution contains 0.1 M HCl. If 10 mL of this solution is added to 100 mL of 0.1 M NaOH, what is the pH of the resulting solution?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 21

A metal (M) has a density of 10 g/cm^3. If a 2.0 g sample of M is dissolved in 100 mL of solvent, what is the concentration of the solution?

A. 0.1 M

Correct B. 1.0 M

C. 10 M

D. 100 M

Correct Answer: B

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Question 22

A solution contains 0.1 M NaOH. If 10 mL of this solution is added to 100 mL of 0.1 M HCl, what is the pH of the resulting solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 23

A metal (M) has a density of 10 g/cm^3. If a 2.0 g sample of M is dissolved in 100 mL of solvent, what is the concentration of the solution?

A. 0.1 M

Correct B. 1.0 M

C. 10 M

D. 100 M

Correct Answer: B

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Question 24

A solution contains 0.1 M HCl. If 10 mL of this solution is added to 100 mL of 0.1 M NaOH, what is the pH of the resulting solution?

A. 1

B. 2

C. 3

D. 4

Correct Answer: VIEW ANSWER

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Question 25

The reaction between potassium permanganate and oxalic acid is a classic example of a redox reaction. The balanced equation for this reaction is: \( 2KMnO_4 + 5H_2C_2O_4 + 3H_2SO_4 \rightarrow K_2SO_4 + 2MnSO_4 + 10CO_2 + 8H_2O \). What is the oxidation state of manganese in the product \( MnSO_4 \)?

A. 0

Correct B. +2

C. -2

D. +4

Correct Answer: B

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