Railway Science (Chemistry-Solutions)

Total Questions: 42

31. Mixture can be _________in nature. [RRB JE 02/06/2019 (Evening)]

Correct Answer: (b) Both homogeneous and heterogeneous
Solution:

Homogeneous mixture - It is a uniform composition throughout the mixture and has only one phase of matter. Example - Mixture of salt and water, mixture of water and sugar.

32. What is the relative density of a substance? [RRB JE 26/06/2019 (Evening)]

Correct Answer: (c) Density of substance / density of water
Solution:

33. Colloid is a ________. [RPF Constable 04/02/2019 (Morning)]

Correct Answer: (a) Heterogeneous Mixture
Solution:

Heterogeneous Mixture - It is a non - uniform mixture with visible, individual items or particles. It has two or more phases. Examples - Mixture of sand and water, mixture of oil, Colloid and water.
Foam: It is a mixture of air and liquid. Where air or gas is trapped inside a fluid. Example - whipped Cream.
Emulsion: A mixture of two or more liquids that are normally immiscible owing to liquid-liquid phase separation. Examples - Milk (a mixture of water and fat).

34. Which of the following is a surface phenomenon? [RRB ALP Tier - I (13/08/2018) Morning]

Correct Answer: (c) Evaporation
Solution:

Evaporation - A process by which water is transformed from liquid to gaseous state. Surface phenomenon occur at liquid (highly mobile) and solid interphase boundaries; Examples - Surface tension, Adsorption, Heterogeneous Catalysis, Corrosion.

35. Which of the following processes will take place the slowest for the same quantity of liquid? [RRB ALP Tier - I (14/08/2018) Afternoon]

Correct Answer: (a) Evaporation
Solution:

Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. Boiling point of water at sea level is 100°C (212°F).

36. Which of the following methods will separate water from muddy water? [RRB ALP Tier - I (29/08/2018) Afternoon]

Correct Answer: (a) Filtration
Solution:

Filtration - Process of separating solid particles from a liquid or gaseous mixture by using filters. Various filtration processes and their uses: Churning (centrifugation process) - To separate cream from milk. Decanting is the process of separation of liquid from solid and other immiscible (non-mixing) liquids, by removing the liquid layer at the top from the layer of solid or liquid below. Sieving - Separating particles of different sizes.

37. If 10⁴ dm³ of water is poured into a 1.0-dm³ flask at 300 K, how many moles of water precipitate will be in vapor state when equilibrium is established? (Given: Vapor pressure of H₂O at 300 K is 3170 Pa; R 8.314 JK.⁻¹ mol⁻¹) [RRB Group D 11/12/2018 (Evening)]

Correct Answer: (d) 1.27 × 10-3 mol
Solution:

Given that : Volume of flask (V) = 1 dm³ ,
Temperature (T) = 300 K,
Vapour Pressure of water (P) = 3170 Pa, Gas
constant (R) = 8.314 JK⁻¹mol⁻¹. Applying Ideal Gas Law to the vapour phase,

38. Equal masses of ethane and hydrogen are mixed in an empty vessel at 25 °C. What is the fraction of total pressure exerted by hydrogen? [RRB Group D 14/12/2018 (Afternoon)]

Correct Answer: (b) 15 : 16
Solution:

39. The amount of BaSO₄ formed on mixing an aqueous solution of 2.08gm of BaCl₂ and excess of dilute H₂SO₄ is _______. (atomic weights: Ba = 137, Cl 35.5, S = 32, O = 16 ) [RRB ALP Tier - I (10/08/2018) Evening]

Correct Answer: (d) 2.33 g
Solution:

40. The percentage of carbon in CO2 is: [RRB ALP Tier - I (14/08/2018) Afternoon]

Correct Answer: (d) 27.3
Solution:

To obtain the percentage of any element in a compound, one needs to take the individual atomic mass of the element and divide it by the total molecular mass of both the compounds.
Mass of carbon = 12 Mass of oxygen = 16 as there are 2 oxygen (16 × 2 = 32)
Percentage of C = 12/32 + 12 = 0.2727 = 0.2727 × 100 = 27.21%
Hence, the percentage of carbon in CO₂ is approximately 27.3.