Railway Science (Chemistry-Chemical Properties)

Total Questions: 52

31. _________ are electropositive in nature. [RRB Group D 25/09/2018 (Afternoon)]

Correct Answer: (b) Metals
Solution:

They generally have 1, 2 or 3 electrons in their valence shells and readily lose these electrons to form positively charged ions. Non-metals have a tendency to take electrons and get converted into a negatively charged ion and therefore are electronegative.

32. Zinc can separate copper from copper sulphate solution because zinc: [RRB Group D 26/09/2018 (Afternoon)]

Correct Answer: (b) is more reactive than copper.
Solution:

The reaction involved in this process : Zn + CuSO₄ →ZnSO₄ + Cu. Relative reactivities of metals from most reactive to least reactive: Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Mercury, Silver and Gold.

33. White phosphorus is stored in: [RRB Group D 28/09/2018 (Afternoon)]

Correct Answer: (d) Water
Solution:

White phosphorus is a translucent white waxy solid. White phosphorus is generally stored under water due to its high reactivity with oxygen in the air. The burning of phosphorus produces dense, white, irritating smoke containing mixed phosphorus oxides

34. 'Alum' is an example of: [RRB Group D 28/09/2018 (Afternoon)]

Correct Answer: (d) Double salt
Solution:

When a mixture containing equimolar proportions of potassium sulphate and aluminium sulphate or ferrous sulphate and ammonium sulphate is crystallised from its solution, a double salt is formed. Examples - Mohr’s salt (FeSO₄ .(NH₄)₂SO₄ . 6H₂O), potash alum (K2SO₄ .Al₂(SO₄)₃ .24H₂O) etc.

35. In which of the following is MgCl₂ soluble? [RRB Group D 03/10/2018 (Morning)]

Correct Answer: (d) Water
Solution:

Magnesium chloride (MgCl₂): Inorganic compound and forms hydrates MgCl₂ .nH₂O (where n ranges from 1 to 12). It is insoluble in acetone. Acetone (CH₃)₂CO): organic compound known as Propanone. It is colorless, highly volatile and flammable liquid and simplest and smallest ketone.

36. Which of the following mixtures of carbon has the highest temperature of liquefaction and boiling ? [RRB Group D 05/10/2018 (Afternoon)]

Correct Answer: (a) Acetic acid
Solution:

Factors Affecting Liquefaction (melting) and Boiling Points: Intermolecular forces - Stronger intermolecular forces require more energy to overcome, leading to higher liquefaction and boiling points and Molecular weight.

37. Which of the following options is not a property of covalent compounds? [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (b) High melting and boiling points
Solution:

Covalent compounds - The molecules that form when two different atoms form a covalent bond. The properties of covalent compounds: Low melting and boiling point, Weak conductor of heat and electricity, Insoluble in water and soluble in organic solvents.

38. Which of the following solutions do not conduct electricity ? [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (b) sugar
Solution:

When sugar dissolves in water, it forms molecules dispersed throughout the water, but these molecules do not dissociate into ions. Therefore, sugar solutions do not contain free ions capable of carrying an electric current.

39. In a molecule of water, the ratio of hydrogen and oxygen (H : O) is _________. [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (d) 2 : 1
Solution:

Each molecule of water (H2O) contains two hydrogen atoms (H) bonded to one oxygen atom (O). Therefore, the ratio of hydrogen atoms to oxygen atoms in a molecule of water is 2:1

40. Which are the two chemicals that are used in black and white photography? [RRB Group D 15/10/2018 (Afternoon)]

Correct Answer: (a) AgCl and AgBr
Solution:

Chemical reaction - 2AgCl (s) → 2Ag (s) + Cl₂(g) → . 2AgBr → 2Ag(s) + Br₂ . Light is absorbed in this reaction so it is an endothermic reaction. Sodium thiosulfate (sodium hyposulfite), Na₂S₂O₃ is used by photographers to fix developed negatives and prints; it acts by dissolving the part of the silver salts coated onto film which remain unchanged by exposure to light.