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POST UTME EKSU 2018 Chemistry | Objective

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Question 1

Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of potassium chlorate (KClO3) decompose according to the equation: 2KClO3(s) → 2KCl(s) + 3O2(g).

A. 1.5 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 5 moles

Correct Answer: C

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Question 2

A 2.5 M solution of sodium hydroxide (NaOH) is mixed with a 2.5 M solution of hydrochloric acid (HCl). What is the pH of the resulting solution?

A. 1

Correct B. 7

C. 10

D. 14

Correct Answer: B

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Question 3

A diagram of a titration setup is shown below. What is the purpose of the burette in this setup?

A. To measure the volume of the acid

Correct B. To measure the volume of the base

C. To mix the acid and base

D. To measure the pH of the solution

Correct Answer: B

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Question 4

A 1.0 M solution of calcium chloride (CaCl2) is mixed with a 1.0 M solution of sodium carbonate (Na2CO3). What is the resulting solution?

Correct A. A precipitate forms

B. No reaction occurs

C. A gas is released

D. A solution forms

Correct Answer: A

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Question 5

A diagram of a redox reaction is shown below. What is the oxidation state of the manganese ion in the compound MnO2?

A. +2

B. +4

Correct C. +6

D. +8

Correct Answer: C

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Question 6

At 273 K, 1.00 L of an ideal gas at 1.00 atm occupies a volume of 22.4 L. What is the volume occupied by 2.00 moles of the same gas at 1.00 atm and 273 K?

Correct A. 44.8 L

B. 22.4 L

C. 11.2 L

D. 5.6 L

Correct Answer: A

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Question 7

A solution contains 25.0 g of glu\cose (C6H12O6) dissolved in 100.0 mL of water. What is the molarity of the solution?

A. 0.250 M

B. 0.500 M

Correct C. 1.00 M

D. 2.00 M

Correct Answer: C

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Question 8

The half-life of a radioactive subs\tance is 5.00 days. If 100.0 mg of the subs\tance is initially present, how much will remain after 20.0 days?

A. 12.5 mg

Correct B. 25.0 mg

C. 50.0 mg

D. 100.0 mg

Correct Answer: B

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Question 9

A 2.00 M solution of HCl is titrated with a 1.00 M solution of NaOH. If 25.0 mL of NaOH is required to reach the equivalence point, what is the volume of HCl used?

Correct A. 50.0 mL

B. 25.0 mL

C. 12.5 mL

D. 6.25 mL

Correct Answer: A

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Question 10

A 1.00 L solution contains 0.100 mol of NaCl. What is the concentration of the solution in g/L?

A. 10.0 g/L

Correct B. 20.0 g/L

C. 30.0 g/L

D. 40.0 g/L

Correct Answer: B

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Question 11

A sample of an ideal gas is heated from 300 K to 400 K at cons\tant volume. Calculate the change in entropy (ΔS) of the gas, given that the molar heat capacity at cons\tant volume (Cv) is 20.8 J/mol·K.

A. 10.3 J/K

Correct B. 20.6 J/K

C. 30.9 J/K

D. 41.2 J/K

Correct Answer: B

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Question 12

The s\tandard enthalpy of formation (ΔHf) of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1 mole of C6H12O6(s) to form CO2(g) and H2O(l).

Correct A. -2803.0 kJ/mol

B. -2803.5 kJ/mol

C. -2804.0 kJ/mol

D. -2804.5 kJ/mol

Correct Answer: A

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Question 13

A 2.50-g sample of an unknown hydrocarbon is burned in a bomb calorimeter, and the temperature of the calorimeter decreases by 2.50°C. If the calorimeter has a heat capacity of 1.50 kJ/°C, calculate the heat of combustion of the hydrocarbon.

A. -6.75 kJ/g

Correct B. -6.85 kJ/g

C. -6.95 kJ/g

D. -7.05 kJ/g

Correct Answer: B

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Question 14

The atomic radius of a certain element is 0.125 nm. If the element has a crystal structure with a lattice parameter of 0.500 nm, calculate the density of the element.

A. 2.50 g/cm³

Correct B. 2.55 g/cm³

C. 2.60 g/cm³

D. 2.65 g/cm³

Correct Answer: B

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Question 15

A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. Calculate the molar mass of the repeating unit.

A. 200 g/mol

Correct B. 250 g/mol

C. 300 g/mol

D. 350 g/mol

Correct Answer: B

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Question 16

A solution of 0.1 M NaCl is mixed with a solution of 0.1 M AgNO3. The reaction is as follows: Ag+ + 2Cl- → AgCl (s) + Na+ . If the initial volume of the NaCl solution is 100 mL and the initial volume of the AgNO3 solution is 50 mL, what is the concentration of AgCl (s) formed after the reaction is complete?

A. 0.033 M

B. 0.066 M

Correct C. 0.1 M

D. 0.133 M

Correct Answer: C

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Question 17

A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?

A. 100 g/mol

B. 150 g/mol

Correct C. 200 g/mol

D. 250 g/mol

Correct Answer: C

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Question 18

A solution of 0.1 M HCl is mixed with a solution of 0.1 M NaOH. The reaction is as follows: HCl + NaOH → NaCl + H2O. If the initial volume of the HCl solution is 100 mL and the initial volume of the NaOH solution is 50 mL, what is the pH of the resulting solution?

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 19

A sample of a non-metallic element has a mass of 2.5 g and a volume of 1.5 cm3. What is the density of the element?

A. 1.5 g/cm3

Correct B. 1.67 g/cm3

C. 2.0 g/cm3

D. 2.5 g/cm3

Correct Answer: B

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Question 20

A solution of 0.1 M H2SO4 is mixed with a solution of 0.1 M NaOH. The reaction is as follows: H2SO4 + 2NaOH → Na2SO4 + 2H2O. If the initial volume of the H2SO4 solution is 100 mL and the initial volume of the NaOH solution is 50 mL, what is the concentration of Na2SO4 formed after the reaction is complete?

A. 0.033 M

B. 0.066 M

Correct C. 0.1 M

D. 0.133 M

Correct Answer: C

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Question 21

The reaction of cyclohexane with bromine in the presence of light produces a mixture of 1,2-dibromocyclohexane and 1,4-dibromocyclohexane. Which of the following statements is correct regarding the relative reactivity of the two products?

A. 1,2-dibromocyclohexane is more reactive than 1,4-dibromocyclohexane.

Correct B. 1,4-dibromocyclohexane is more reactive than 1,2-dibromocyclohexane.

C. Both products are equally reactive.

D. The reactivity of the two products cannot be determined.

Correct Answer: B

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Question 22

A colloidal solution of starch in water is negatively charged. What is the likely reason for this charge?

A. The starch molecules have a negative charge.

B. The water molecules have a negative charge.

Correct C. The starch molecules are surrounded by a layer of negatively charged ions.

D. The starch molecules are surrounded by a layer of positively charged ions.

Correct Answer: C

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Question 23

The enthalpy change for the reaction 2NO(g) → N2(g) + O2(g) is -179.6 kJ/mol. What is the s\tandard enthalpy of formation of NO(g)?

Correct A. -90.8 kJ/mol

B. -179.6 kJ/mol

C. 90.8 kJ/mol

D. 179.6 kJ/mol

Correct Answer: A

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Question 24

The element with atomic number 16 is?

Correct A. Sulfur

B. Phosphorus

C. Chlorine

D. Argon

Correct Answer: A

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Question 25

The reaction of sodium hydroxide with hydrochloric acid produces a gas that is released into the atmosphere. What is the name of this gas?

A. Carbon dioxide

B. Nitrogen

Correct C. Hydrogen chloride

D. Water vapor

Correct Answer: C

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