Part Test 4

Which of the following reactions is correct for a given electrochemical cell at 25°C ?

Pt | Br₂(g)|Br^–(g)|| cl^– (aq)|Cl₂(g)|Pt

1. 2Br^–(aq) + Cl₂(g) à2Cl^– (aq) + Br₂(g)
2. Br₂(g) + 2Cl^–(aq) à 2Br^–(aq) + Cl₂(g)
3. Br₂(g) + Cl₂(g) à 2Br^–(aq) + 2Cl^–(aq)
4. 2Br^–(aq) + 2Cl^–(aq) à Br₂(g) + Cl₂(g)

Which is not the oxidation reduction electrode?

(1) Pt | Fe²⁺ , Fe³⁺

(2) Pt | Sn⁴⁺, Sn²⁺

(3)

(4) None of these

If the half cell reaction A + e^– àA^– has a large negative potential, if follows that

The correct value of e.m.f. of cell is given by

(i) E_cell = E_OP anode – E_RP cathode

(ii) E_cell = E_op anode + E_RP cathode

(iii) E_cell =  E_RP anode – E_RP cathode

(iv) E_cell = E_OP anode – E_OP cathode

If the equilibrium constant of the disproportionation reaction at 298 K is 0.0795, the standard emf of the reaction is

For the cell

Pb (s) | Pb²⁺ (aq) (1M) ||Cu²⁺ (aq) (1M) | Cu (s) ;

E⁰ = +0.47 V. If the concentration of Pb⁺² ions is reduced to 0.1 M, the emf of the cell would change  to

The cell Pt (H₂), (1 atm) | H⁺ (pH = 2) || I^– (a=1) | AgI(s), Ag has emf, E_298k=0. The electrode potential of the reaction AgI+e^– àAg + I^– is – 0.151V. calculate the pH value

The electrode potentials for

Cu²⁺ (aq) + e^– à  Cu⁺(aq) and

Cu⁺(aq) + e^– à Cu(s) are + 0.15 V and +0.50 V respectively. The value of E⁰_Cu2+/Cu will be

A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as

Given that at 25⁰C

[Ag(NH₃)₂]⁺+e^–à Ag(s)+ 2NH₃ E⁰ = 0.02 V

And Ag⁺ + e^– à Ag(s) E⁰ = 0.8 V

Hence the order of magnitude of the equilibrium constant of the reaction will be

(antilog 0.22=1.66)

For a reaction R –> P given below

∆H for this reaction

For the first order reaction Reactant à Product carried out at 27⁰C. If 3.8*10^-16% of the reactant molecules exist in activated state then activation energy (Ea) of the reaction is

For a reaction N₂ + 3H₂ à 2NH₃

_{if(∆[NH3])/∆t)=} 2*10^-4 mol L^-1 S^-1

The value of –(∆[H2])/∆t) would be

For a reaction A+2B –> 3C get interested 72 times when concentration of A is tripled and that of B is doubled . The order of reaction w.r.t. A and B are respectively

For a chemical reaction at 27⁰C, activation energy 600R. The ratio of rate constant at 327⁰C to that of 27⁰C will be

A reaction is 50% completed in 2 hours and 75% completed in 4 hours. The order of reaction is

When Ethyle acetate is hydrolyzed in presence of 0.1 M HCl, the rate constant was found to be 5.4*10^-5S^-1. But in presence of 0.1 M H₂SO₄, the rate constant was found to be 6.25*10^-5S^-1. Thus it may be concluded that

Rate constant for reaction is 1.5*10⁷ sec^-1 at 50⁰C and 4.5*10⁷ sec^-1 at 100⁰C what is the value of activation energy?

For a particular reaction rate constant, K= 2.303 min^-1. The initial concentration of reactant is 1 mol/litre . Then rate of reaction after 1 minute is :

Following are the values of E_a and ∆H for three reactions carried out at the same temperature

I :  E_a = 20 kJ mol^-1, ∆H = -60 kJ mol^-1

II : E_a = 10 kJ mol ^-1 , ∆H = -20 kJ mol^-1

III : E_a = 40 kJ mol^-1, ∆H= +15 kJ mol^-1

If the three reaction have same frequency factor then fastest and slowest reaction are

Which is not true for a second order reaction ?

A reaction of first order completed 90% in 90 min hence it is complete 50% in

.  For a reaction activation energies of both forward and backward reaction is equal. Then which of the following is correct ?

.           For the reaction

2NO + Br₂ à 2NOBr

The following Mechanism has been given

Hence rate low is

(1) K[NO]²[Br]               (2)  K[NO][Br₂]

(3) K[NOBr₂][NO]          (4)  K[NO][Br₂]²

For a reaction A(g) à B(g) + C(g) rate law is =K[A]. At start pressure is 100 mm and after 10 min pressure is 120 mm, hence  rate constant (min^-1) is

For a reaction, A –>B, E_a = 10 kJ mol^-1 and ∆H = 5 KJ mol^-1. Thus potential energy profile for this reaction

Graph between log K vs 1/T is a straight line. If OX = 5 and slope of of line = -1/2.303. Then Ea is

This question has Statement I and Statement II. Of the four  choices given after the Statements, choose the one that best describes the two Statements.

1. Statement – I : The acid-catalysed hydrolysis of an ester is a pseudo-unimoleculer reaction.
2. Statement-II : Hydrolysis of ester proceeds at constant concentration of H⁺.

What will happen if ligaments are cut or broken?

Hair present in the skin are

This is the difference between a nerve and a neuron

Crossing over occurs between

In anaphase of mitosis

Which of the following pair is correctly matched ?

The effective resistance between points P and Q of the electrical circuit shown in the figure is

. Six identical resistors are connected as shown in the figure. The equivalent resistance will be

Find the electric field at a distance r from the center

A material B has twice the specific resistance of the material A. A circular wire made of B has twice the diameter of the wire made of A. Then , for the two wires to have to have the same resistance, the ratio L_a/L_b of their respective lengths must be

Resistivity of the material of a conductor having uniform area of cross-section varies along its length according to the relation
ρ= ρ₀ (a+bx)
if L is the length of the conductor and be the area of cross-section then resistivity of the conductor given by relation

If a wire is stretched to make it 0.1% longer, its resistance will

Consider the figure given below

If ammeter shows a reading of 10A and voltmeter having internal resistance 3000 Ω measures a voltage of 200V, the resistance R is given by

Four capacitors are connected as shown below in the figure

Here C₁=2μF , C₂=3μF , C₃=4μF and C₄=5μF. The equivalent capacitance between A and B is

A point charge q is located at (2, 3, 3) in xyz coordinate. Find the potential differences between A and B
A = (2, 3, 3)
B = (-2, 3, 3)

If the voltage across a bulb decreases by 1%, then the percentage change in its power output is :

In the figure a carbon resistor has bands of different colours on its body as mentioned in the figure. The value of the resistance is 

Masses of 3 wires of same metal are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1. The electrical resistances are in ratio

A copper wire has a square cross-section, 2.0 mm on a side. It carries a current of 8 A and the density of free electrons is 8 × 10²⁸ m^–3. The drift speed of electrons is equal to 

A current of 2 A flows in a system of conductors as shown. The potential difference (VA−VB) will be 

Two resistances are joined in parallel whose resultant is 6868 ohm. One of the resistance wire is broken and the effective resistance becomes 2Ω. Then the resistance in ohm of the wire that got broken was

In the given figure, potential difference between A and B is

A parallel plate capacitor is charged and the charging battery is then disconnected. If the plates of the capacitor are moved further apart by means of insulating handles, then 

What is the area of the plates of a 3F parallel plate capacitor, if the separation between the plates is 5 mm ?

A parallel plate condenser is filled with two dielectrics as shown. Area of each plate is A metre² and the separation is t metre. The dielectric constants are k₁ and k₂ respectively. Its capacitance in farad will be

The capacities and connection of five capacitors are shown in the adjoining figure. The potential difference between the points A and B is 60 volts. Then the equivalent capacity between A and B and the charge on 5 μF capacitance will be respectively

In the adjoining figure, four capacitors are shown with their respective capacities and the P.D. applied. The charge and the P.D. across the 4 μF capacitor will be

100 capacitors each having a capacity of 10 μF are connected in parallel and are charged by a potential difference of 100 kV. The energy stored in the capacitors and the cost of charging them, if electrical energy costs 108 paise per kWh, will be 

The plates of a capacitor are charged to a potential difference of 320 volts and are then connected across a resistor. The potential difference across the capacitor decays exponentially with time. After 1 second the potential difference between the plates of the capacitor is 240 volts, then after 2 and 3 seconds the potential difference between the plates will be 

The variation of potential with distance R from a fixed point is as shown below. The electric field at R = 5 m is 

When a piece of aluminum wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become :

A cell whose e.m.f. is 2 V and internal resistance is 0.1 Ω, is connected with a resistance of 3.9 Ω. The voltage across the cell terminal will be :

Eels are able to generate current with biological cells called electro plaques. The electro plaques in an eel are arranged in 100 rows, each row stretching horizontally along the body of the fish containing 5000 electro plaques. The arrangement is suggestively shown below. Each electro plaques has an emf of 0.15 V and internal resistance of 0.25 Ω 

The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of 500 Ω, the current an eel can produce in water is about

The equivalent resistance of the following infinite network of resistances is 

Kirchhoff’s first law i.e. Σi=0 at a junction is based on the law of conservation of :

In the given figure, the equivalent resistance between the points A and B