Raji Ram answered • 1 hour ago

Average time of existence of an unstable or reactive entity.

t(mean) = 1.443*t(half)

http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/nuclear/meanlif.html

t(mean) = 1.443*t(half)

http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/nuclear/meanlif.html

Namita Sharma asked • just now

Two Carnot engines A and B are operated in series. The first one, A, receives heat at T_{1}(= 600 K) and rejects to a reservoir at temperature T_{2}. The second engine B receives heat rejected by the first engine and, in turn, rejects to a heat reservoir at T_{3}(= 400 K). Calculate the temperature T_{2} if the work outputs of the two engines are equal :

- a)400 K
- b)600 K
- c)500 K
- d)300 K

Correct answer is option 'C'. Can you explain this answer?

The half-life period of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years is [NCERT 1980; SCRA 1994; JIPMER 1997 CBSE PMT 1994; MNR 1998; MP PMT 2004; DPMT 2004]

- a)1/4
- b)1/2
- c)1/8
- d)1/16

Correct answer is option 'D'. Can you explain this answer?

Raji Ram answered • 1 hour ago

There are three containers C_{1}, C_{2} and C_{3} filled with same material at different constant temperature. When we mix then for different volume then we get some final temperature as shown in the below table. So find value of final temperature θ as shown in the table.

Correct answer is '50'. Can you explain this answer?

Raji Ram answered • 1 hour ago

Refer this link for explanation

https://www.toppr.com/ask/question/three-containers-c-1-c-2-c-3/

https://www.toppr.com/ask/question/three-containers-c-1-c-2-c-3/

Three containers C1, C2 and C3 have water at different temperatures. The table below shows the final

temperature T when different amounts of water (given in liters) are taken from each container and

mixed (assume no loss of heat during the process The value of θ (in °C to the nearest integer) is____

temperature T when different amounts of water (given in liters) are taken from each container and

mixed (assume no loss of heat during the process The value of θ (in °C to the nearest integer) is____

Correct answer is '50'. Can you explain this answer?

Raji Ram answered • 1 hour ago

Refer this link for explanation

https://www.toppr.com/ask/question/three-containers-c-1-c-2-c-3/

https://www.toppr.com/ask/question/three-containers-c-1-c-2-c-3/

The e.m.f. of a galvanic cell with electrode potentials of silver equal to + 0.80 V and that of copper equal to + 0.34 V is

- a)- 0.46 V
- b)- 1.14 V
- c)+0.46 V
- d)+1.14 V

Correct answer is option 'C'. Can you explain this answer?

Raji Ram answered • 1 hour ago

Electrode potential of Ag is greater than Cu

Ag is cathode and Cu is anode

emf = E(cathode) - E(anode) = 0.8 - 0.34 = 0.46V

Ag is cathode and Cu is anode

emf = E(cathode) - E(anode) = 0.8 - 0.34 = 0.46V

The e.m.f. of a galvanic cell with electrode potentials of Al equal to -1.66 V and that of Mg equal to - 0.54 V is

- a)+ 0.44 V
- b)+ 1.12 V
- c)- 0.44 V
- d)- 1.12 V

Correct answer is option 'D'. Can you explain this answer?

Raji Ram answered • 1 hour ago

Electrode potential Mg is greater than EP of Al .
Hence Al is anode and Mg is cathode.
emf = E(cathode) - E(anode) = -0.54- (-1.66) = 1.12V
option B is correct not D
if emf is - ve the reaction is not feasible

The e.m.f. of a galvanic cell with electrode potentials of Al equal to -1.66 V and that of Mg equal to - 0.54 V is

- a)+ 0.44 V
- b)+ 1.12 V
- c)- 0.44 V
- d)- 1.12 V

Correct answer is option 'D'. Can you explain this answer?

Raji Ram answered • 1 hour ago

Electrode potential Mg is greater than EP of Al .
Hence Al is anode and Mg is cathode.
emf = E(cathode) - E(anode) = -0.54- (-1.66) = 1.12V
option B is correct not D
if emf is - ve the reaction is not feasible

The *I.P.* of sodium is 5.14*eV*. The *I.P.* of potassium could be

- a)Same as that of sodium
- b)5.68eV
- c)4.34eV
- d)10.28eV

Correct answer is option 'C'. Can you explain this answer?

Raji Ram answered • 2 hours ago

IP of K should be less than IP of Na as IP decreases moving down the group.

Radioactivity was discovered by

- a)Becquerel
- b)Pierre Curie
- c)Roentgen
- d)Rutherford

Correct answer is option 'A'. Can you explain this answer?

Raji Ram answered • 2 hours ago

Https://www.whodiscoveredit.com/who-discovered-radioactivity.html

An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let λ_{n},λ_{g} be the de Broglie wavelength of the electron in the n^{th} state and the ground state respectively. Let ∧_{n} be the wavelength of the emitted photon in the transit ion fro m the n^{th} state to the ground state. For large n, (A, B are constants)

- a)
- b)
- c)
- d)

Correct answer is option 'C'. Can you explain this answer?

Raji Ram answered • 2 hours ago

Find n (A – B) from the figure

- a)1
- b)2
- c)4
- d)3

Correct answer is option 'B'. Can you explain this answer?

Kottakalva Murali answered • 2 hours ago

A=,{4,6,10} B={6,8}

A-B={4,10}. n(A-B)=2 elements

A-B={4,10}. n(A-B)=2 elements

Upma Sharma asked • 45 minutes ago

The electric charge for electrode deposition of one gramequivalent of a substance is : (1984 - 1 Mark)

- a)one ampere per second.
- b)96,500 coloumbs per second.
- c)one ampere for one hour.
- d)charge on one mole of electrons.

Correct answer is option 'D'. Can you explain this answer?

If a set is empty then number of subsets will be

- a)1
- b)2
- c)0
- d)4

Correct answer is option 'A'. Can you explain this answer?

Khaja Moinuddin answered • 4 hours ago

A set will always be a subset of itself so an empty set is also the subset of an empty set...but a coincidence every empty set is a subset of every set by this way also we can say that an empty set is also a subset of an empty set...so the answer is 1 and that one set is an empty set itself

O Kaif Sid asked • 2 hours ago

There are 6 roads between A & B and 4 roads between B & C

(i) In how many ways can one drive from A to C by way of B ?

(ii) In how many ways can one drive from A to C and back to A, passing through B on both trips ?

(iii) In how many ways can one drive the circular trip described in (ii) without using the same road more than once.

Correct answer is '(i)Â 24 ;Â (ii)Â 576;Â (iii)Â 360'. Can you explain this answer?

Geeta Devi asked • 3 hours ago

For positive integers n_{1}, n_{2} the value of the expression (1 + i)^{n1} + (1 + i^{3})^{n1} + (1+ i^{5})^{n2} + (1+i^{7})^{n2} , where i = – is a real number if and only if (1996 - 1 Marks)

- a)n
_{1 }= n_{2}+1 - b)n
_{1}= n_{2 }–1 - c)n
_{1}= n_{2} - d)n
_{1}> 0, n_{2}> 0

Correct answer is option 'D'. Can you explain this answer?

Niladrita Chakraborty asked • 3 hours ago

In a radioactive substance at t=0, the number of atoms is 8×10^{4}. Its half life period is 3 years. The number of atoms 1×10^{4} will remain after interval [MP PMT/PET 1988]

- a)9 years
- b)8 years
- c)6 years
- d)24 years

Correct answer is option 'A'. Can you explain this answer?

Luxmi Devi asked • 4 hours ago

Let z_{1} and z_{2} be complex numbers such that and the roots α and β of x^{2} + z_{1}x + z^{2} + m = 0 for some complex number m satisfies

- a)straight line
- b)circle
- c)ellipse
- d)hyperbola

Correct answer is option 'B'. Can you explain this answer?

Prachetas Nair asked • 4 hours ago

The displacement of a body from a reference point is given by,(√x) = 2t-3 where ' x ' is in metres and t in seconds. This shows that the body :

- a)is at rest at t = 3/2
- b)is accelerated
- c)is decelerated
- d)is in uniform motion

Correct answer is option 'A,B'. Can you explain this answer?

Pranjali Subhedar asked • 4 hours ago

In a class of 50 students, 20 play Hockey, 15 play Cricket and 11 play Football. 7 play both Hockey and Cricket, 4 play Cricket and Football and 5 play Hockey and football. If 18 students do not play any of these given sports, how many students play exactly two of these sports?

- a)12
- b)10
- c)11
- d)15

Correct answer is option 'B'. Can you explain this answer?

Mohinder Singh Chhoker asked • 6 hours ago

Statement-1 : When ultraviolet light is incident on a photocell, its stopping potential is V_{0} and the maximum kinetic energy of the photoelectrons is K_{max }. When the ultraviolet light is replaced by X-rays, both V_{0} and K_{max} increase.

Statement-2 : Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.

- a)Statement-1 is true, Statement-2 is false
- b)Statement-1 is false, Statement-2 is true
- c)Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-1
- d)Statement-1 is true, Statement-2 is true; Statement-2 is the not the correct explanation of Statement-1

Correct answer is option 'A'. Can you explain this answer?

Krishan Sobti asked • 6 hours ago

Direction (Q. No. 17) Choices for the correct combination of elements from Column I and Column II are given as options (a), (b), (c) and (d), out of which one is correct.

- a)a
- b)b
- c)c
- d)d

Correct answer is option 'D'. Can you explain this answer?

Shakuntla asked • 6 hours ago

Passage V

The following first order reaction is conducted in CCI_{4}(l)at 45°.

An 80.0 g sample of N_{2}O_{5}(g)is dissolved inCCI_{4}(l) and allowed to decompose at 450°C.

- a)1.553 h
- b)0.674 h
- c)3.577 h
- d)None of these

Correct answer is option 'A'. Can you explain this answer?

Maina Devi asked • 6 hours ago

A chemical reaction is known to be zeroth order with k = 5 x 10^{-8} mol s^{-1}. The reaction takes t_{1} seconds to decrease concentration from 4 x 10^{-4} mol dm^{-3} to 2 x 10^{-4} mol dm^{-3} and t_{2} seconds to decrease concentration from 2 x 10^{-4} mol dm^{-3} to 1 x 10^{-4} mol dm J What is the ratio of t_{1} to t_{2}?

Correct answer is '2'. Can you explain this answer?

Kamla Devi asked • 6 hours ago

Passage II

The complex ion of Fe^{2+} with the chelating agent diphyridyl (abbreviated as dipy) has been studied kinetically in both the forward and the reverse directions.

- a)17.30
- b)-17.30
- c)0.0578
- d)- 0.0578

Correct answer is option 'B'. Can you explain this answer?

Sunita asked • 6 hours ago

For the reaction,

In alkaline aqueous solution, the value of the second order (in BrC^{-}), rate constant at 80°C in the rate law for was found to be 0.056 L mol^{-1} s^{-1}

- a)or the rate law rate constant is 0.019 L mol
^{-1}s^{-1} - b)for the rate law rate constant is 0.037 L mol
^{-1}s^{-1} - c)it is a redox reaction
- d)it is a disproportionation reaction

Correct answer is option 'A,B,C,D'. Can you explain this answer?

Pushpa Devi asked • 6 hours ago

Passage IV

The rate constant for the decomposition of ethylene oxide into CH_{4} and CO may be described by

- a)4.8x 10-5 Ms
^{-1} - b)4,8x 10
^{-5}s^{-1} - c)4.8x 10
^{-2}Ms^{-1} - d)4.8x 10
^{-2}s^{-1}

Correct answer is option 'B'. Can you explain this answer?

Maya Devi asked • 6 hours ago

For the bimolecular reaction

The rate constant is k = 1 .3 x 10^{10} L mol ^{-1} s^{-1}

Compare the initial value of d/dt [O] for [O] = [OH] = 1.0 x 10^{-4} mol L^{-1} to that [O] = 1.0 x 10^{-4} mol L^{-1} and [OH]= 2.0 x 10^{-4} mol L^{-1}

Compare the initial value of d/dt [O] for [O] = [OH] = 1.0 x 10

Correct answer is '2'. Can you explain this answer?

Diwan Chand asked • 6 hours ago

Chemical reactions are invariably associated with transfer of energy miner in form of heat or light. In the laboratory, heat changes in physical and chemical processes are measured with an instrument called calorimeter. Heat change in the process is calculated as

q = ms Δ T s = specific heat J/K-gm

=C Δ T C = heat capacity J/K

In Bomb calorimeter measurement are taking at constant volume.

So heat of reaction at constant volume :

So heat of reaction at constant volume :

q = ΔU (Internal energy change)

Here heat is released by combustloin so sign of AU and heat should be negative. In water colarimeter measurement are taking at constant pressure.

So, qp = Δ H

So, qp = Δ H

q_{p} = q_{v} + P Δ V

Δ H = Δ U + Δ n_{g}RT

Match the list-I and list-II and select the answer : List-I (Unbalanced reaction)

Malkeet Kaur asked • 6 hours ago

A train approaching a railway platform with a speed of 20 ms^{–1 }starts blowing the whistle. Speed of sound in air is 340 ms^{–1}. If the frequency of the emitted sound from the whistle is 640 Hz, the frequency of sound to a person standing on the platform will appear to be

- a)600 Hz
- b)640 Hz
- c)680 Hz
- d)720 Hz

Correct answer is option 'C'. Can you explain this answer?

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