Civil Engineering GATE 2025 Set-2 Questions with Answer

Ques 14 Environmental Engineering

Free residual chlorine concentration in water was measured to be 2 mg/l (as Cl₂). The pH of water is 8.5. By using the chemical equation given below, the HOCl concentration (in μmoles/l) in water is ______ (round off to one decimal place).
HOCl↔H⁺+OCl^-. pK=7.50
Atomic weight: Cl(35.5)

Ques 15 Environmental Engineering

A compound has a general formula C_aH_bO_cN_d and molecular weight 187. A 935 mg/l solution of the compound is prepared in distilled deionized water. The Total Organic Carbon (TOC) is measured as 360 mg/l (as C). The Chemical Oxygen Demand (COD) and the Total Kjeldahl Nitrogen (TKN) are determined as 600 mg/l (as O₂) and 140 mg/l (as N), respectively (as per the chemical equation given below). Which of the following options is/are CORRECT?
C_aH_bO_cN_d + (4a+b-2c-3d)/4 O₂ → aCO₂ + (b-3d)/2 H₂O + dNH₃
Atomic weight: C(12), H(1), O(16), N(14)

Ques 16 Environmental Engineering

The analyses results of a water sample are given below. The non-carbonate hardness of the water (in mg/L) as CaCO₃ is ______ (in integer).
Ca²⁺=150 mg/L as CaCO₃
Mg²⁺=40 mg/L as CaCO₃
Fe²⁺=10 mg/L as CaCO₃
Na⁺=50 mg/L as CaCO₃
K⁺=10 mg/L as CaCO₃
CO₃^2-=120 mg/L as CaCO₃
HCO₃^-=30 mg/L as CaCO₃
Cl^-=50 mg/L as CaCO₃; Other anions were not analysed.

Ques 17 Environmental Engineering

A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is 250 m³, and the biomass concentration in the tank is 3000 mg/L. Analyses results showed that a biomass concentration of 10 mg/L is present in the treated effluent from the secondary sedimentation tank of the ASP. Sludge wastage from the system is at a rate of 5000 L/day with a biomass concentration of 10000 mg/L. The system is in steady state condition.
The biological sludge residence time (BSRT) of the system (in days) is ______ (round off to one decimal place).

Ques 18 Environmental Engineering

A settling chamber is used for the removal of discrete particulate matter from air with following conditions. Horizontal velocity of air =0.2 m/s; Temperature of air stream =77°C: Specific gravity of particle to be removed =2.65; Chamber length =12m Chamber height =2 m; Viscosity of air at 77°C=2.1×10^-5 kg/m.s Acceleration due to gravity (g)=9.81 m/s² Density of air at 77°C=1.0 kg/m³ Assume the density of water as 1000 kg/m³ and Laminar condition exists in the chamber.
The minimum size of particle that will be removed with 100% efficiency in the settling chamber (in μm) is ______ (round off to one decimal place).

Ques 19 Fluid Mechanics

A hydraulic jump occurs in an open channel when the slope of the channel changes from

Ques 20 Fluid Mechanics

Consider steady flow of water in the series pipe system shown below, with specified discharge. The diameters of Pipes A and B are 2 m and 1 m, respectively. The lengths of pipes A and B are 100 m and 200 m, respectively. Assume the Darcy-Weisbach friction coefficient, f as 0.01 for both the pipes.
The ratio of head loss in Pipe-B to the head loss in Pipe-A is ______ (round off to the nearest integer).

Ques 21 Fluid Mechanics

Consider flow in a long and very wide rectangular open channel. Width of the channel can be considered as infinity compared to the depth of flow. Uniform flow depth is 1.0 m. The bed slope of the channel is 0.0001. The Manning roughness coefficient value is 0.02. Acceleration due to gravity, g can be taken as 9.81 m/s².
The critical depth (in m) corresponding to the flow rate resulting from the above conditions is ______ (round off to one decimal place).

Ques 22 Fluid Mechanics

The drag force, F_D on a sphere due to a fluid flowing past the sphere is a function of viscosity, μ, the mass density, ρ, the velocity of flow, V, and the diameter of the sphere, D.
Pick the relevant (one or more) non-dimensional parameter(s) pertaining to the above process from the following list.

Ques 23 Fluid Mechanics

The shaft of a 6 m wide gate in the figure will fail at a moment of 3924 kN.m about the hinge P. The maximum value of water depth h (in m) that the gate can hold is ______ (round off to the nearest integer).
Note:
Density of water =1000 kg/m³
Acceleration due to gravity =9.81 m/s²

Ques 24 General Aptitude

Even though I had planned to go skiing with my friends, I had to ______ at the last moment because of an injury.
Select the most appropriate option to complete the above sentence.

Ques 25 General Aptitude

The President, along with the Council of Ministers, ______ to visit India next week.
Select the most appropriate option to complete the above sentence.

Ques 26 General Aptitude

An electricity utility company charges ¥7 per kWh (kilo watt-hour). If a 40-watt desk light is left on for 10 hours each night for 180 days, what would be the cost of energy consumption? If the desk light is on for 2 more hours each night for the 180 days, what would be the percentage-increase in the cost of energy consumption?