Fill in the blanks with appropriate items :
The half-life period of radioactive element _______ minute if 75% of it disintegrates in 40 min.
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The half-life period of a radioactive element is `1.4 xx 10^(10)` years. Calculate the time in which the activity of the element is reduced to 90% of
`t_(1//2) = 0.693/k or k=0.693/t_(//2)= 0.693/(1.4 xx 10^(10)`years `t=2.303/k log N_(0)/N_(t) = 2.303/(0.693 // 1.4 xx 10^(10) years) xx log 100/90` `= 2.303/0.693 xx 1.4 xx 10^(10) xx 0.4558` years...
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The half - line period a radioactive element `X` is same as the mean life time of another radioactive element `Y`. Initially both of them have the sam
Correct Answer - B Given that `(T_(1//2))_(x) = (T_(av))_(gamma)` `rArr (0.693)/(lambda_(x)) = (1)/(lambda_(y)) rArr lambda_(y) (1)/(0.693) lambda_(x)` `rArr lambda_(y) = 1.44 lambda_(x) rArr R_(y) = 1.44 R_(x)` As decay rate of...
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Two radioactive nuclides A and B have half-lives 50 min and 10 min respectively . A fresh sample contains the nuclides of B to be eight times that of
Correct Answer - C Initial no. of nuclei `{:(Aoverset(t_(1//2)=50 min)rarrX,,B overset(t_(1//2)=10 min)rarrX),(N_(0),,8N_(0)),(,,),(,,):}` Let after n `t_(1//2)` of A, no. of nuclei of A becomes double of B. `N_(A)=(N_(0))/(2^(n)) " " N_(B)=(8N_(0))/(2 ^(5n))...
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Fill in the blanks with appropriate items : The `alpha` -activity of `1 gm .^(226) Ra. (t_(1//2)=1620 ` year) is _______ dpm.
Correct Answer - `2.16 xx 10^(12) dpm` `A=N lambda =((1)/(226)xxN_(A)) xx(0.693)/(1620 xx12 xx24xx30xx60)` `2.16 xx 10^(-12)` d.p.m
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Fill in the blanks with appropriate items : The half life of the nuclide `Rn^(220)` is `54.5 sec`., _______ kg of radon is equivalent to 1 millicurie.
Correct Answer - `1.06 xx 10^(-15)` `A=Nlambda` ` 1xx10^(-3) xx3.7 xx10^(10)` d.p.s `=Nxx(0.693)/(54.5) " " ` 1curie`=3.7 xx 10^(10)` d.p.s. `N=290.98 xx10^(7) rArr (N)/(N_(A))=(29.98 xx10^(7))/(6.023 xx10^(23))=48.31 xx 10^(-16)` moles Mass of...
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Fill in the blanks with appropriate items : A radioactive substance decays 20% in 10 min if at start there are ` 5 xx 10^(20)` atoms present , after _
Correct Answer - `4.65` `k=(1)/(10) ln .(100)/(80) =(1)/(t) "in" (5xx10^(20))/(10^(18)) rArr (1)/(10)"in"(5)/(4)=(1)/(t) "in" 500 rArr (10 xx"in" 500)/("ln"(5)/(4))` `t=278.5` min. `t=4.641` hr.
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True or False Statements : Half life for certain radioactive element is 15 min. Four nuclei of that element are observed at a certain instant of time.
Correct Answer - [F] Calculation is applicable on the large amount of ratio active substance and it is propable.
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A radioactive substance disintegrates 1/64 of initial value in 60 s. The half-life of this substance is
Correct Answer - B We have , `1/64=((1)/(2))^(n)n=6` 6 half-lives are equal to 60 s. `therefore` 1 half-life = 10 s
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Assertion In one half-life of a radioactive substance more number of nuclei are decayed than in one average life. Reason Average life = Half -life/in
Correct Answer - D (d) Average life is more Hence more nuclei decay in one avaerage life .
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At 500 K, the half-life period of a gaseous reaction at the initial pressure of 80 kPa is 350 sec. When the pressure is 40 kPa, the half life period i
`((t_(1//2))_(1))/((t_(1//2))_(2))=((p_(2))/(p_1))^(n-1)` `(350)/(175)=((40)/(80))^(n-1)` `2=((1)/(2))^(n-1)` n-1=-1 n=0 (zero order reaction)
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