Experimental determination of __________ is done by wetted wall column method. (A) Diffusion co-efficient (B) Mass transfer co-efficient (C) NTU (D) None of these

Experimental determination of __________ is done by wetted wall

column method.

(A) Diffusion co-efficient

(B) Mass transfer co-efficient

(C) NTU

(D) None of these

by

1 Answer

Answer :

(B) Mass transfer co-efficient

by

Related questions

For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is (A) Calculated (B) Unknown (C) Known (D) Not required

Description : For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is (A) Calculated (B) Unknown (C) Known (D) Not required

Last Answer : (C) Known

Laboratory determination of the diffusivity of vapor is done by __________ method. (A) Wetted wall column (B) Gilliland's (C) Winkelmann's (D) Wike's

Description : Laboratory determination of the diffusivity of vapor is done by __________ method. (A) Wetted wall column (B) Gilliland's (C) Winkelmann's (D) Wike's

Last Answer : (C) Winkelmann's

The wetted wall tower is used to determine (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system (B) M.T.C. of individual components in a liquid-liquid system (C) M.T.C. of liquid in liquid-gas system (D) The overall M.T.C. of the system

Description : The wetted wall tower is used to determine (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system (B) M.T.C. of individual components in a liquid-liquid system (C) M.T.C. of liquid in liquid-gas system (D) The overall M.T.C. of the system

Last Answer : (A) Individual mass transfer co-efficient (M.T.C.) in gaseous system

Wetted wall tower experiment determines the (A) Molal diffusivity (B) Volumetric co-efficient (C) Mass transfer co-efficient (D) None of these

Description : Wetted wall tower experiment determines the (A) Molal diffusivity (B) Volumetric co-efficient (C) Mass transfer co-efficient (D) None of these

Last Answer : (C) Mass transfer co-efficient

__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids. (A) Wetted wall (B) Packed (C) Plate (D) Spray

Description : __________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids. (A) Wetted wall (B) Packed (C) Plate (D) Spray

Last Answer : C) Plate

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ column. (A) Spray (B) Packed (C) Bubble cap plate (D) Wetted wall

Description : Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ column. (A) Spray (B) Packed (C) Bubble cap plate (D) Wetted wall

Last Answer : (D) Wetted wall

__________ column is used in gas absorption process. (A) Wetted wall (B) Sieve/perforated tray (C) Bubble cap (D) Packed

Description : __________ column is used in gas absorption process. (A) Wetted wall (B) Sieve/perforated tray (C) Bubble cap (D) Packed

Last Answer : (D) Packed

Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the (A) Mass transfer co-efficient (B) Thermal diffusivity (C) Kinematic viscosity (D) Volumetric diffusivity

Description : Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the (A) Mass transfer co-efficient (B) Thermal diffusivity (C) Kinematic viscosity (D) Volumetric diffusivity

Last Answer : (A) Mass transfer co-efficient

Pick out the wrong statement. (A) Mass transfer co-efficient does not account for gas-liquid diffusion (B) Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation

Description : Pick out the wrong statement. (A) Mass transfer co-efficient does not account for gas-liquid diffusion (B) Diffusion co-efficient and mass transfer co-efficient are not same in any mass transfer operation

Last Answer : (A) Mass transfer co-efficient does not account for gas-liquid diffusion

Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. (A) Surface renewal (B) Film (C) Penetration (D) None of these

Description : Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. (A) Surface renewal (B) Film (C) Penetration (D) None of these

Last Answer : (B) Film

Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty? (A) Sieve plate column (B) Bubble cap column (C) Randomly packed column (D) Wetted wall column

Description : Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty? (A) Sieve plate column (B) Bubble cap column (C) Randomly packed column (D) Wetted wall column

Last Answer : (D) Wetted wall column

Which of the following equipments is used for liquid dispersion? (A) Packed column (B) Venturi scrubber (C) Bubble cap plate column (D) Wetted wall column

Description : Which of the following equipments is used for liquid dispersion? (A) Packed column (B) Venturi scrubber (C) Bubble cap plate column (D) Wetted wall column

Last Answer : Option B

Mass transfer co-efficient is directly proportional to DAB 0.5 , according to __________ theory. (A) Penetration (B) Surface renewal (C) Film (D) None of these

Description : Mass transfer co-efficient is directly proportional to DAB 0.5 , according to __________ theory. (A) Penetration (B) Surface renewal (C) Film (D) None of these

Last Answer : (A) Penetration

Mass transfer co-efficient is directly proportional to DAB according to the __________ theory. (A) Film (B) Penetration (C) Surface-renewal (D) None of these

Description : Mass transfer co-efficient is directly proportional to DAB according to the __________ theory. (A) Film (B) Penetration (C) Surface-renewal (D) None of these

Last Answer : (A) Film

The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm2 /sec. (A) 0.25 (B) 2.5 (C) 1.25 (D) 0.0025

Description : The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm2 /sec. (A) 0.25 (B) 2.5 (C) 1.25 (D) 0.0025

Last Answer : (A) 0.25

Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 (D) The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Description : Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed ... flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Last Answer : (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2

The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp= M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) (A) Kc = Kp = Km (B) Kc = Kp /RT = Km . RT/P (C) Kc = Kp . RT = Km . RT/p (D) None of these

Description : The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving ... (C) Kc = Kp . RT = Km . RT/p (D) None of these

Last Answer : (C) Kc = Kp . RT = Km . RT/p

Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower. (A) Wetted wall (B) Bubble cap (C) Perforated tray (D) Packed

Description : Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower. (A) Wetted wall (B) Bubble cap (C) Perforated tray (D) Packed

Last Answer : (A) Wetted wall

________ Equation predicts the activity co-efficient from experimental data. (A) Lewis-Randall (B) Margules (C) Van Laar (D) Both (B) & (C)

Description : ________ Equation predicts the activity co-efficient from experimental data. (A) Lewis-Randall (B) Margules (C) Van Laar (D) Both (B) & (C)

Last Answer : (D) Both (B) & (C)

As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient (A) Continues to increase (B) Continues to decrease (C) Goes through a minimum (D) Goes through a maximum

Description : As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient (A) Continues to increase (B) Continues to decrease (C) Goes through a minimum (D) Goes through a maximum

Last Answer : (C) Goes through a minimum

. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Description : . The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C ... from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Last Answer : (A) 165.4

Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is ‘3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?(A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Description : Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l'. If the wall temperature ... wall temperature in degree centigrade? (A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Last Answer : (C) 81.25

Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s (D) The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Description : Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In ... layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Last Answer : (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s

For absorbing a sparingly soluble gas in a liquid (A) Gas side mass transfer co-efficient should be increased (B) Liquid side mass transfer co-efficient should be increased (C) Liquid side mass transfer co-efficient should be decreased (D) Mass transfer co-efficient must be kept constant

Description : For absorbing a sparingly soluble gas in a liquid (A) Gas side mass transfer co-efficient should be increased (B) Liquid side mass transfer co-efficient should be increased (C) Liquid side mass transfer co-efficient should be decreased (D) Mass transfer co-efficient must be kept constant

Last Answer : (B) Liquid side mass transfer co-efficient should be increased

Mass transfer co-efficient of liquid is (A) Affected more by temperature than that for gases (B) Affected much less by temperature than that for gases

Description : Mass transfer co-efficient of liquid is (A) Affected more by temperature than that for gases (B) Affected much less by temperature than that for gases

Last Answer : (A) Affected more by temperature than that for gases

Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as (A) K ∝ D (B) K ∝√D (C) K ∝ D1.5 (D) K ∝ D

Description : Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as (A) K ∝ D (B) K ∝√D (C) K ∝ D1.5 (D) K ∝ D

Last Answer : (A) K ∝ D

The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by (A) Increasing the gas film co-efficient(B) Increasing the liquid film co-efficient(C) Increasing the total pressure(D) Decreasing the total pressure

Description : The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by (A) Increasing the gas film co-efficient (B) Increasing the liquid film co-efficient (C) Increasing the total pressure (D) Decreasing the total pressure

Last Answer : (A) Increasing the gas film co-efficient

Which of the following is not a unit of mass transfer co-efficient? (A) Moles transferred/ [(time) (area) (mole fraction)] (B) Moles transferred/ [(time) (area) (mass A/mass B)] (C) Moles transferred/ [(time) (area) (pressure)] (D) None of these

Description : Which of the following is not a unit of mass transfer co-efficient? (A) Moles transferred/ [(time) (area) (mole fraction)] (B) Moles transferred/ [(time) (area) (mass A/mass B)] (C) Moles transferred/ [(time) (area) (pressure)] (D) None of these

Last Answer : (D) None of these

Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as (A) D0.5 (B) D (C) 1/D (D) D1.5

Description : Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as (A) D0.5 (B) D (C) 1/D (D) D1.5

Last Answer : (A) D0.5

In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL ) as (A) KG = 1/KG + m/KL (B) 1/KG = 1/KG + m/KL (C) 1/KG = 1/KL + m/KG (D) KG = 1/KL + m/KG

Description : In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL ) as (A) KG = 1/KG + m/KL (B) 1/KG = 1/KG + m/KL (C) 1/KG = 1/KL + m/KG (D) KG = 1/KL + m/KG

Last Answer : (B) 1/KG = 1/KG + m/KL

Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as (A) K ∝D (B) K ∝√D (C) K ∝D1.5 (D) K ∝D

Description : Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as (A) K ∝D (B) K ∝√D (C) K ∝D1.5 (D) K ∝D

Last Answer : (B) K ∝√D

The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is(A) 100(B) 10(C) 5(D) 1.

Description : The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is. (A) 100 (B) 10 (C) 5 (D) 1

Last Answer : (B) 10

The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume of quiescent liquid, in which ‘D’ is the diffusivity of solute, is (A) D/a (B) D/2a (C) Proportional to √D (D) Dependent on the Reynolds number

Description : The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume of quiescent liquid, in which ‘D’ is the diffusivity of solute, is (A) D/a (B) D/2a (C) Proportional to √D (D) Dependent on the Reynolds number

Last Answer : (D) Dependent on the Reynolds number

Mass transfer co-efficient is defined as (A) Flux = Co-efficient/concentration difference (B) Co-efficient = Flux/concentration difference (C) Flux=concentration difference/coefficient (D) None of these

Description : Mass transfer co-efficient is defined as (A) Flux = Co-efficient/concentration difference (B) Co-efficient = Flux/concentration difference (C) Flux=concentration difference/coefficient (D) None of these

Last Answer : (B) Co-efficient = Flux/concentration difference

Pick out the wrong statement. (A) In a first order reaction, A → products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration of A (B) Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes (C) According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases (D) If the rate of an irreversible reaction, A + B → 2C is k.CA .CB , then the reaction is always elementary

Description : Pick out the wrong statement. (A) In a first order reaction, A → products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration ... irreversible reaction, A + B → 2C is k.CA .CB , then the reaction is always elementary

Last Answer : (C) According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases

Pick out the correct statement. (A) The slope of the stripping line is always less than unity (B) For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distillation column first increases and then decreases (C) In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux (D) Kremser-Brown-Souder's equation is used to calculate the efficiency of a plate tower

Description : Pick out the correct statement. (A) The slope of the stripping line is always less than unity (B) For a given separation in a binary distillation column, with increase in reflux ratio ( ... (D) Kremser-Brown-Souder's equation is used to calculate the efficiency of a plate tower

Last Answer : C) In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux

Binary distillation involves the mass transfer by __________ at the gas￾liquid interface. (A) Unidirectional diffusion from liquid to gas phase (B) Unidirectional diffusion from gas to liquid phase (C) Either 'a' or 'b' (D) A counter diffusion at an almost equal molar rate

Description : Binary distillation involves the mass transfer by __________ at the gas￾liquid interface. (A) Unidirectional diffusion from liquid to gas phase (B) Unidirectional diffusion from gas to liquid phase (C) Either 'a' or 'b' (D) A counter diffusion at an almost equal molar rate

Last Answer : (D) A counter diffusion at an almost equal molar rate

Gaseous diffusion co-efficient increases with increase in the (A) Pressure (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : Gaseous diffusion co-efficient increases with increase in the (A) Pressure (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (B) Temperature

The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is (A) 2.09 × 10 -4 (B) 2.09 × 10 -5 (C) 2.09 × 10 -9 (D) 2.09 × 10 -12

Description : The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is (A) 2.09 × 10 -4 (B) 2.09 × 10 -5 (C) 2.09 × 10 -9 (D) 2.09 × 10 -12

Last Answer : (A) 2.09 × 10 -4 (B) 2.09 × 10 -5

Which of the following is not a dimension-less group used in catalysis? (Where, D = dispersion co-efficient, cm2 /sec.D1 = diffusion co-efficient; cm2 /sec L = length of the reactor, cm t = time, sec, v = volumetric flow rate, cm3 /sec. V = volume, cm3 .) (A) Reactor dispersion number (D/vL) (B) Reduced time (vt/V) (C) Thiele modulus L √(k/D1 ) (D) None of these

Description : Which of the following is not a dimension-less group used in catalysis? (Where, D = dispersion co-efficient, cm2 /sec.D1 = diffusion co-efficient; cm2 /sec L = length of the reactor, cm t = time, sec, v = volumetric ... (D/vL) (B) Reduced time (vt/V) (C) Thiele modulus L √(k/D1 ) (D) None of these

Last Answer : (D) None of these

The effectiveness factor for large value of Thiele modulus [L√(K/D1 )] of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D1 = diffusion co-efficient, cm2 /second). (A) L √(K/D1 ) (B) 1/[L√(K/D1 )] (C) 1 (D) ∞

Description : The effectiveness factor for large value of Thiele modulus [L√(K/D1 )] of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D1 = diffusion co-efficient, cm2 /second). (A) L √(K/D1 ) (B) 1/[L√(K/D1 )] (C) 1 (D) ∞

Last Answer : (B) 1/[L√(K/D1 )]

Diffusion co-efficient of a metal in a solid solution depends upon its (A) Composition (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : Diffusion co-efficient of a metal in a solid solution depends upon its (A) Composition (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Description : Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Last Answer : (D) Highly turbulent

Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. (A) No (B) The least (C) The largest (D) Lower

Description : Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. (A) No (B) The least (C) The largest (D) Lower

Last Answer : (C) The largest

Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C. (A) 10-50 (B) 100-500 (C) 1000-1500 (D) 5000-15000

Description : Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C. (A) 10-50 (B) 100-500 (C) 1000-1500 (D) 5000-15000

Last Answer : (D) 5000-15000

The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Description : The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Last Answer : (B) 4 0.8

The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. (A) Greater than (B) Lower than (C) Is same as (D) Half

Description : The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. (A) Greater than (B) Lower than (C) Is same as (D) Half

Last Answer : (B) Lower than

A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Description : A thin, flat & square plate measuring 2 m 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will ... heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Last Answer : (B) 100