CHEMISTRY (Part-III) (Railway)

Total Questions: 50

1. Which of the following statements is, are true or false? [RRB ALP & Technician Exam, 31.08.2018 Shift-III]

Statements:

I. H₂S burns in air to give H₂O and SO₂

II. The decomposition of Ferrous Sulphate into Fe₂O₃ , SO₂ and SO₃ occurs in the presence of heat.

(1) Statements I and II both are true.
(2) Statement I is true, while B is false.
(3) Statements I and II are false.
(4) Statement II is true, while I is false.

Correct Answer: (1) Statements I and II both are true.

Solution:Hydrogen Sulphide gas burns in air to give water and Sulphur dioxide. On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate (FeSO) is formed. So their colour changes from light green to white. On further heating, anhydrous ferrous sulphate decomposes to form ferric oxide (Fe₂O), sulphur dioxide (SO₂) and sulphur trioxide (SO).

2. Which of the following metal is not obtained by electrolytic reduction? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

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

Correct Answer: (4) Iron

Solution:Electrolytic reduction is the method of reducing metals with the help of electrolysis. Metals that are placed high in the reactivity series are highly electropositive and they cannot be reduced by carbon as reducing agent. The oxides, hydroxide and chlorides of metals in fused state are electrically reduced by electrolytic reduction. Metals like Sodium (Na). K (Potassium), Mg (Magnesium), Ca (calcium), Aluminium (Al) are ob tained by this process.

3. 2Cu + O₂ → 2CuO. The given reaction is an example of a: [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) Combination reaction
(2) Decomposition reaction
(3) Double displacement reaction
(4) Displacement reaction

Correct Answer: (2) Decomposition reaction

Solution:A combination reaction, also known as synthesis, is a chemical reaction in which two or more substances combine to form a single substance under suitable conditions. Copper combines with oxygen to form Copper Oxide. 2Cu + O₂ + Heat ⇒ 2CuO is also an example of oxidation reaction since copper gets oxygen and hence is oxidised.

4. Which of the following statements is/are correct in relation to graphite and diamond? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

I. Their electronic configurations are different

II. They have identical chemical properties

III. Their atoms are bounded to each other differently

IV. The process of obtaining metals from their compounds is known as Oxidation?

(1) II, III and IV
(2) I, II and III
(3) I, II and IV
(4) I, II, III and IV

Correct Answer: (2) I, II and III

Solution:Diamond and graphite are both allotropes of carbon: they are both made entirely of the same element (carbon) but they differ in the way that the atoms bond with each other and arrange themselves in a structure. So, while they have similar chemical properties. their electronic configurations are different. The process of procuring metals from ores is called metallurgy and these naturally occurring compounds of metals are known as minerals.

5. What is the chemical formula of Plaster of Paris? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) CaSO₄.2H₂O
(2) CaSO₄.H₂O
(3) K₂SO₄.2H₂O
(4) CaSO₄.½H₂O

Correct Answer: (4) CaSO₄.½H₂O

Solution:Plaster of Paris is a quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate). which hardens when moistened and allowed to dry. It is produced by heating gypsum to about 150 °C.

CaSO₄.2H₂O + heat → CaSO₄.0.5H₂O + 1.5 H₂O (released as steam)

6. Which of the following is a decomposition reaction? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) 2Mg + O₂ → 2MgO
(2) Zn + H₂SO₄ → ZnSO₄ + H₂
(3) CH₄[g] + 2O₂[g] → CO₂[g] + 2H₂O[g] + energy
(4) 2KClO₃(s) + heat → 2KCl(s)+ 3O₂(g)

Correct Answer: (4) 2KClO₃(s) + heat → 2KCl(s)+ 3O₂(g)

Solution:If in a chemical reaction a single substance decomposes to form two or more substances then it is known as a decomposition reaction. In the given case, Potassium Chlorate (KClO₃) is decomposed or broken down into Potassium Chloride (KCl) and Oxygen.

7. Which metal will displace hydrogen from dilute acids? [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

(1) Hg
(2) Zn
(3) Ag
(4) Cu

Correct Answer: (2) Zn

Solution:All the metals which are present above hydrogen in the reactivity series can displace hydrogen gas from dilute acids. This is because these acids are more reactive than hydrogen. Examples include zinc, calcium, magnesium etc. for example, in the reaction of zinc and dilute sulphuric acid. hydrogen is displaced.

Zn + H₂SO₄ → ZnSO₄ + H₂

8. The Law of Octaves was applicable only till the element ________ . [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-I]

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

Correct Answer: (3) Calcium

Solution:According to Newlands' law of octaves when the elements are arranged in order of increasing atomic weights then every eighth element has properties similar to that of the first element. It was applicable only upto calcium, as after calcium, every eighth element does not possess properties similar to that of the first.

9. Select the INCORRECT statement with respect to properties of an acid from the given options. [RRB RPF/RPSF SI Exam, 04.09.2018 Shift-III]

(1) Acids turn blue litmus to red.
(2) Most of the acids react with metals to form salts and evolve hydrogen gas.
(3) Acid solution conducts electricity.
(4) Acids have a bitter taste.

Correct Answer: (4) Acids have a bitter taste.

Solution:Acids taste sour, are corrosive to metals and become less acidic when mixed with bases. An acid will turn litmus paper red. Litmus is a vegetable dye that turns red to indicate an acid and blue to indicate a base.

10. Fossils fuels are rich in carbon and: [RRB RPF/RPSF SI Exam. 04.09.2018 Shift-III]

(1) Oxygen
(2) Chlorine
(3) Carbon dioxide
(4) Hydrogen

Correct Answer: (4) Hydrogen

Solution:Fossil fuels are hydrocarbons formed from the remains of dead plants and animals. Fossil fuels principally consist of carbon and hydrogen bonds. There are three types of fossil fuels which can all be used for energy provision: coal, oil and natural gas.

12 3 4 5 Next »