JEE
If the half life of radium is1600 year. Then mean life of radium is?And explain about mean life?
Raji Ram answered • 1 hour agoAverage 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 nowTwo Carnot engines A and B are operated in series. The first one, A, receives heat at T1(= 600 K) and rejects to a reservoir at temperature T2. The second engine B receives heat rejected by the first engine and, in turn, rejects to a heat reservoir at T3(= 400 K). Calculate the temperature T2 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?
Two Carnot engines A and B are operated in series. The first one, A, receives heat at T1(= 600 K) and rejects to a reservoir at temperature T2. The second engine B receives heat rejected by the first engine and, in turn, rejects to a heat reservoir at T3(= 400 K). Calculate the temperature T2 if the work outputs of the two engines are equal :
a)
400 K
b)
600 K
c)
500 K
d)
300 K
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?
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
Raji Ram answered • 1 hour ago
There are three containers C1, C2 and C3 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?
There are three containers C1, C2 and C3 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.
Raji Ram answered • 1 hour agoRefer 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____ 
Correct answer is '50'. Can you explain this answer?
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____
Raji Ram answered • 1 hour agoRefer 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?
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
Raji Ram answered • 1 hour agoElectrode 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?
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
Raji Ram answered • 1 hour agoElectrode 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?
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
Raji Ram answered • 1 hour agoElectrode 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 5.14eV. 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?
The I.P. of sodium is 5.14eV. The I.P. of potassium could be
a)
Same as that of sodium
b)
5.68eV
c)
4.34eV
d)
10.28eV
Raji Ram answered • 2 hours agoIP 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?
Radioactivity was discovered by
a)
Becquerel
b)
Pierre Curie
c)
Roentgen
d)
Rutherford
Raji Ram answered • 2 hours agoHttps://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 λn,λg be the de Broglie wavelength of the electron in the nth state and the ground state respectively. Let ∧n be the wavelength of the emitted photon in the transit ion fro m the nth 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?
An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let λn,λg be the de Broglie wavelength of the electron in the nth state and the ground state respectively. Let ∧n be the wavelength of the emitted photon in the transit ion fro m the nth state to the ground state. For large n, (A, B are constants)
a)
b)
c)
d)
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?
Find n (A – B) from the figure
a)
1
b)
2
c)
4
d)
3
Kottakalva Murali answered • 2 hours agoA=,{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 agoThe 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?
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.
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?
If a set is empty then number of subsets will be
a)
1
b)
2
c)
0
d)
4
Khaja Moinuddin answered • 4 hours agoA 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
Mitul Chakraborty asked • 1 hour agoa point starts moving in a straight line with a certain acceleration .At a time t after beginning of motion the acceleration suddenly becomes retardation of the same value .The total time in which the point returns to the w initial position is.? Related: Introduction to Motion?
Related: Introduction to Motion
O Kaif Sid asked • 2 hours agoThere 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?
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.
Geeta Devi asked • 3 hours agoFor positive integers n1, n2 the value of the expression (1 + i)n1 + (1 + i3)n1 + (1+ i5)n2 + (1+i7)n2 , where i = – 
is a real number if and only if (1996 - 1 Marks)- a)n1 = n2 +1
- b)n1 = n2 –1
- c)n1 = n2
- d)n1 > 0, n2 > 0
Correct answer is option 'D'. Can you explain this answer?
For positive integers n1, n2 the value of the expression (1 + i)n1 + (1 + i3)n1 + (1+ i5)n2 + (1+i7)n2 , where i = – is a real number if and only if (1996 - 1 Marks)
is a real number if and only if (1996 - 1 Marks)a)
n1 = n2 +1
b)
n1 = n2 –1
c)
n1 = n2
d)
n1 > 0, n2 > 0
Niladrita Chakraborty asked • 3 hours ago In a radioactive substance at t=0, the number of atoms is 8×104. Its half life period is 3 years. The number of atoms 1×104 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?
In a radioactive substance at t=0, the number of atoms is 8×104. Its half life period is 3 years. The number of atoms 1×104 will remain after interval [MP PMT/PET 1988]
a)
9 years
b)
8 years
c)
6 years
d)
24 years
Luxmi Devi asked • 4 hours agoLet z1 and z2 be complex numbers such that 
and the roots α and β of x2 + z1x + z2 + m = 0 for some complex number m satisfies 
Q. The locus of the complex number m is a curve - a)straight line
- b)circle
- c)ellipse
- d)hyperbola
Correct answer is option 'B'. Can you explain this answer?
Let z1 and z2 be complex numbers such that and the roots α and β of x2 + z1x + z2 + m = 0 for some complex number m satisfies
and the roots α and β of x2 + z1x + z2 + m = 0 for some complex number m satisfies Q.
The locus of the complex number m is a curve
a)
straight line
b)
circle
c)
ellipse
d)
hyperbola
Prachetas Nair asked • 4 hours agoThe 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?
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
Pranjali Subhedar asked • 4 hours agoIn 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?
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
in the expansion of 
are non-coplanar vectors then
Mohinder Singh Chhoker asked • 6 hours agoStatement-1 : When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is Kmax . When the ultraviolet light is replaced by X-rays, both V0 and Kmax 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?
Statement-1 : When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is Kmax . When the ultraviolet light is replaced by X-rays, both V0 and Kmax 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
Krishan Sobti asked • 6 hours agoDirection (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.Q. Rate law of the nth order reaction is given by
Match the different properties in Column I with their related values of half-life in Column II and select the correct answer from the codes given.
- a)a
- b)b
- c)c
- d)d
Correct answer is option 'D'. Can you explain this answer?
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.
Q. Rate law of the nth order reaction is given by
Match the different properties in Column I with their related values of half-life in Column II and select the correct answer from the codes given.
a)
a
b)
b
c)
c
d)
d
Shakuntla asked • 6 hours agoPassage VThe following first order reaction is conducted in CCI4(l)at 45°.
An 80.0 g sample of N2O5(g)is dissolved inCCI4(l) and allowed to decompose at 450°C.Q. Time taken for the quantity of N2O5 to be reduced to 2.5 g is- 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?
Passage V
The following first order reaction is conducted in CCI4(l)at 45°.
An 80.0 g sample of N2O5(g)is dissolved inCCI4(l) and allowed to decompose at 450°C.
Q.
Time taken for the quantity of N2O5 to be reduced to 2.5 g is
a)
1.553 h
b)
0.674 h
c)
3.577 h
d)
None of these
Maina Devi asked • 6 hours agoA chemical reaction is known to be zeroth order with k = 5 x 10-8 mol s-1. The reaction takes t1 seconds to decrease concentration from 4 x 10-4 mol dm-3 to 2 x 10-4 mol dm-3 and t2 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 t1 to t2?
Correct answer is '2'. Can you explain this answer?
A chemical reaction is known to be zeroth order with k = 5 x 10-8 mol s-1. The reaction takes t1 seconds to decrease concentration from 4 x 10-4 mol dm-3 to 2 x 10-4 mol dm-3 and t2 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 t1 to t2?
and a and b are the initial concentrations of A and B. Reaction w ould be pseudo-unimolecular when
Kamla Devi asked • 6 hours agoPassage IIThe complex ion of Fe2+ with the chelating agent diphyridyl (abbreviated as dipy) has been studied kinetically in both the forward and the reverse directions.
Q. Stability constant in terms of pk is- a)17.30
- b)-17.30
- c)0.0578
- d)- 0.0578
Correct answer is option 'B'. Can you explain this answer?
Passage II
The complex ion of Fe2+ with the chelating agent diphyridyl (abbreviated as dipy) has been studied kinetically in both the forward and the reverse directions.
Q.
Stability constant in terms of pk is
a)
17.30
b)
-17.30
c)
0.0578
d)
- 0.0578
Sunita asked • 6 hours agoFor 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-1Select the correct alternate reaction.- 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?
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
was found to be 0.056 L mol-1 s-1Select the correct alternate reaction.
a)
or the rate law rate constant is 0.019 L mol-1 s-1
rate constant is 0.019 L mol-1 s-1b)
for the rate law rate constant is 0.037 L mol-1 s-1
rate constant is 0.037 L mol-1 s-1c)
it is a redox reaction
d)
it is a disproportionation reaction
Diwan Chand asked • 6 hours agoChemical 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 asq = ms Δ T s = specific heat J/K-gm=C Δ T C = heat capacity J/KIn Bomb calorimeter measurement are taking 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 Hqp = qv + P Δ VΔ H = Δ U + Δ ngRTMatch the list-I and list-II and select the answer : List-I (Unbalanced reaction)
... more
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
qp = qv + P Δ V
Δ H = Δ U + Δ ngRT
Match the list-I and list-II and select the answer : List-I (Unbalanced reaction)
Malkeet Kaur asked • 6 hours agoA 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?
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
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