Chemistry Questions and Answers – P-Block Elements – Chlorine

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This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “P-Block Elements – Chlorine”.

1. What is the molecular mass of chlorine?
a) 71.0 kg/kmole
b) 35.5 g/kmole
c) 71.0 g/kmole
d) 35.5 kg/mole
View Answer

Answer: a
Explanation: In the periodic table, the atomic mass of chlorine atom is 35.5 AMU. Since chlorine exists in diatomic form, the molecular mass = 35.5g/mole x 2 = 71.0 g/mole. On multiplying and dividing by 1000, 71.0 kg/kmole.
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2. Which of the following would instantly react with chlorine?
a) Copper
b) Magnesium
c) Iron
d) Aluminum
View Answer

Answer: b
Explanation: Out of the four metals given, magnesium will readily lose electrons due to its relatively higher reactivity. Copper and iron are not affected by gaseous or liquid chlorine. Lastly, aluminum forms a tough, passive oxide layer which prevents it from reacting with external reagents.

3. What is the color of chlorine?
a) Yellow grey
b) Greenish brown
c) Green yellow
d) Yellow
View Answer

Answer: c
Explanation: Every halogen bears a characteristic color which is used in identifying it. Fluorine is a bright yellow gas. Chlorine is greenish yellow, followed by bromine which is brown and iodine which is purple/violet. Astatine is a black solid which is radioactive in nature.
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4. When excess chlorine reacts with methane in presence of sunlight, which is the major product?
a) Refrigerant – 40
b) Methylene chloride
c) Chloroform
d) Carbon tetrachloride
View Answer

Answer: d
Explanation: In presence of sunlight, a free radical substitution reaction takes place between the reacting methane and chlorine molecules where in each elementary reaction a hydrogen atom is replaced by a chlorine atom in the new product. First, methane converts to 1-chloromethane which in turn produces dichloromethane followed by tri-chloromethane and tetra-chloromethane, respectively.

5. Which of the following is a suitable test to identify presence of chlorine atoms or ions?
a) Acidify the given compound and add silver nitrate
b) Add silver nitrate followed by warming the solution
c) Heat the compound strongly
d) Smell the compound
View Answer

Answer: a
Explanation: The standard, universal qualitative test for detecting presence of chloride is carried out by acidifying the solution and then adding silver nitrate. If chloride ions are present, a thick white ppt. is produced.
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6. Why is chlorine bubbled through water during the latter’s treatment?
a) To remove foul odor
b) To kill microorganisms
c) To improve taste
d) To remove hardness
View Answer

Answer: b
Explanation: Chlorine is a very popular disinfecting agent and is widely used in containers to kill microorganisms. In water treatment plants, chlorine gas may be bubbled through to remove trace quantities of microorganisms.

7. What is the electronic configuration of chloride?
a) 1s22s22p63s23p5
b) 1s22s22p63s23p6
c) 1s22s22p5
d) [Ar]4s24p3
View Answer

Answer: b
Explanation: Chlorine has the atomic number 17. However, chloride has 18 electrons. Consequently, it attains the electronic configuration of argon i.e.1s22s22p63s23p6.
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8. How is chlorine gas manufactured industrially?
a) Deacon process
b) Ostwald process
c) Chlor-alkali process
d) Haber process
View Answer

Answer: c
Explanation: Although Deacon process involves release of chlorine gas as a byproduct, the chief purpose of the deacon process is used to manufacture alkalis. Chlorine is best produced by the chloralkali process, which is the electrolysis of brine, producing hydrogen and chlorine gases as by products.

9. Hydrogen chloride as an acid is much stronger than hydrogen fluoride under the same conditions. True or False?
a) True
b) False
View Answer

Answer: a
Explanation: Fluorine atom is extremely small compared to chlorine. This means that the bond of H – F is much more polar than that of H – Cl, causing the H atom to be more tightly bonded in case of H – F than in H – Cl. Since hydrogen chloride is able to release the H+ much easily, the latter is a stronger acid.
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10. Which of the following is a result of bubbling hydrogen chloride gas through gas?
a) H + Cl
b) H+ + Cl2-
c) H3O+ + Cl
d) H+ + Cl
View Answer

Answer: c
Explanation: The hydrogen chloride molecule, HCl dissociates in water giving rise to one hydrogen ion and a chloride ion. The extremely small hydrogen ion bearing the positive charge is instantly attracted by the unshared pair of electrons of the oxygen atom in water molecules, consequently giving rise to the hydronium ion, H3O+.

11. What will be the result of subjecting a blue litmus to chlorine gas?
a) Turn to red only
b) Remain blue
c) Turn to white finally
d) Turn white in the first go
View Answer

Answer: c
Explanation: Chlorine bears bleaching properties. When blue litmus is subjected to chlorine gas, it first turns red (due to the acidic nature) then it turns white (due to chlorine’s ability to bleach materials).

12. To which group does chlorine element belong?
a) Halides
b) Pre inert
c) Chalcogens
d) Halogens
View Answer

Answer: d
Explanation: Fluorine, chlorine, bromine, iodine and astatine belong to Group 17 of the periodic table. This group is commonly named as Halogens because of their ability to produce salt on reacting with metals.

13. Which of the following is the displays the most basic nature in water?
a) Fluoride
b) Chloride
c) Bromide
d) Iodide
View Answer

Answer: a
Explanation: The fluoride ion is actually not an oxidizing agent. Due to its high electronegativity and high reactivity, it converts water to form hydroxide ions. The reaction is given by 2F + H2O → H – F – H + OH.

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