CHEMISTRY (Part-I) (Railway)

Total Questions: 50

41. The credit for classifying the elements on the basis of their atomic masses goes to: [RRB ALP & Technician Exam. 17.08.2018 Shift-I]

(1) Dmitri Mendeleev
(2) John Dalton
(3) John Alexander Reina Newlands
(4) Johann Wolfgang Dobereiner

Correct Answer: (1) Dmitri Mendeleev

Solution:Dmitri Mendeleev is credited with the systematic classification of elements on the basis of their atomic masses. He developed the periodic classification of the elements. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements.

42. Which of the following metals does NOT react with cold or hot water? [RRB ALP & Technician Exam,17.08.2018 Shift-I]

(1) Sodium
(2) Potassium
(3) Calcium
(4) Aluminium

Correct Answer: (4) Aluminium

Solution:Metals react with water and produce metal oxides and hydrogen gas. The reaction depends upon the reactivity of metals. However, metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

43. Metal oxide which react with acid as well as bases are called: [RRB ALP & Technician Exam,17.08.2018 Shift-I]

(1) Acidic oxide
(2) Neutral oxide
(3) Amphoteric oxide
(4) Basic oxide

Correct Answer: (3) Amphoteric oxide

Solution:In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid and as a base. Many metals (such as copper, zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide.

44. Which one of the following is commonly used as an indicator to measure the exact pH? [RRB ALP & Technician Exam,17.08.2018 Shift-III]

(1) Phenolphthalein
(2) Litmus
(3) Eosin
(4) Universal indicator

Correct Answer: (4) Universal indicator

Solution:(4) A universal indicator is a pH indicator made of a solution of several compounds that exhibits several smooth colour changes over a wide range of pH values to indicate the acidity or alkalinity of solutions. The colours from yellow to red indicate an acidic solution, colours blue to violet indicate bases and green colour indicates that a solution is neutral.

45. What is the atomicity of Phosphorus? [RRB ALP & Technician Exam,17.08.2018 Shift-III]

(1) Mono-atomic
(2) Di-atomic
(3) Tri-atomic
(4) Poly-atomic

Correct Answer: (4) Poly-atomic

Solution:Atomicity is the number of atoms present in a molecule of an element. Molecule consisting of one atom of an element is called monoatomic (He). Molecule consisting 2 atoms are called di atomic (O₂). Molecule consisting 4 atoms are called tetra atomic (P). Molecule consisting of more than 2 atoms are called poly atomic (S).

46. Which of the following metals is a liquid at room temperature? [RRB ALP & Technician Exam,17.08.2018 Shift-III]

(1) Sodium
(2) Lithium
(3) Calcium
(4) Mercury

Correct Answer: (4) Mercury

Solution:Bromine (symbol Br and atomic number 35) and mercury (symbol Hg and atomic number 80) are both liquids at room temperature. Bromine is a reddish-brown liquid, with a melting point of 265.9 K. Mercury is a toxic shiny silvery metal, with a melting point of 234.32 K

47. Which of the following classifications is based on atomic numbers? [RRB ALP & Technician Exam,17.08.2018 Shift-III]

(1) Modern periodic Table
(2) Mendeleev's Periodic Table
(3) Dobereiner's Law of Triads
(4) Newlands Law of Octaves

Correct Answer: (1) Modern periodic Table

Solution:Dmitri Mendeleev was the first chemist to arrange the elements in the periodic table on the basis of atomic mass in 1869. The modern table is based on Mendeleev's table, except the modern table arranges the elements by increasing atomic number instead of atomic mass. Atomic number is the number of protons in an atom, and this number is unique for each element.

48. Aluminium oxide ___________ is nature. [RRB ALP & Technician Exam,17.08.2018 Shift-III]

(1) neutral
(2) acidic
(3) amphoteric
(4) basic

Correct Answer: (3) amphoteric

Solution:(3) An amphoteric compound is a molecule or ion that can react both as an acid and as a base. Many metals (such as copper, zinc, tin, lead, aluminum, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide.

49. Which of the following is used in making perfumes as well as flavouring agents? [RRB ALP & Technician Exam,20.08.2018 Shift-I]

(1) Ethanolc acid
(2) Methanol
(3) Esters
(4) Ethanol

Correct Answer: (3) Esters

Solution:(3) Esters with low molecular weight are commonly used for fragrances and found in essential oils and pheromones. They are made by reacting alcohols and carboxylic acids together in the presence of an acid catalyst. Different combinations of alcohols and carboxylic acids give rise to different esters, and each ester has a unique aroma. These esters are found naturally in fruits and vegetables and are also used in perfumes.

50. Common salt (NaCl) is made up of: [RRB ALP & Technician Exam. 20.08.2018 Shift-I]

(1) a strong acid and a strong base
(2) a weak acid and a weak base
(3) a weak acid and a strong base
(4) a strong acid and a weak base

Correct Answer: (1) a strong acid and a strong base

Solution:Common salt is sodium chloride (NaCl) and consists of sodium cations (Na⁺) and chloride anions (Cl⁻), neither of which are strong bases or acids. However, it is made from reaction of, sodium hydroxide (NaOH) and hydrochloric acid (HCl) that are strong base and acid, respectively.

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