Alpha Decay

Q.

Write differences between a proton and a positron.

Q. What weights of $P_4{O}_6$ and $P_4{O}_{10}$ will be produced by the combustion of 31 g of $P_4$ in 32 g of oxygen leaving no $P_{4}and{O}_2$?

1. 17.5 g, 190.5 g
2. 2.75 g, 219.5 g
3. 55 g, 71 g
4. 27.5 g, 35.5 g

Q. The rate constant for the first order decomposition of $H_2{O}_2$ is given by the following equation:

$logk=14.2-\frac{1.0\times {10}^{4}K}{T}$

Calculate $E_a$ for this reaction and rate constant k of its half-life period be 200 minutes. ( Given: R= $8.314J{K}^{-1}mo{l}^{-1}$

Q. The following facts are available.
$2X^{-}+Y_2⟶2Y^{-}+X_2$
$2W^{-}+Y_2⟶$ No reaction
$2Z^{-}+X_2⟶2X^{-}+Z_2$
Which of the following statements is correct?

1. $E_{W^{-}/W_2}^0>E_{Y^{-}/Y_2}^0>E_{X^{-}/X_2}^0>E_{Z^{-}/Z_2}^0$
2. $E_{W^{-}/W_2}^0<E_{Y^{-}/Y_2}^0<E_{X^{-}/X_2}^0<E_{Z^{-}/Z_2}^0$
3. $E_{W^{-}/W_2}^0<E_{Y^{-}/Y_2}^0>E_{X^{-}/X_2}^0>E_{Z^{-}/Z_2}^0$
4. $E_{W^{-}/W_2}^0>E_{Y^{-}/Y_2}^0<E_{X^{-}/X_2}^0<E_{Z^{-}/Z_2}^0$

Q. A compound contains two elements ${}^{\prime }{X}^{\prime }$ and ${}^{\prime }{Y}^{\prime }$ in the ratio of Mass percentage of $50\%$ each. Atomic mass of ${}^{\prime }{X}^{\prime }$ is 20 and ${}^{\prime }{Y}^{\prime }$ is 40. What can be its simplest formula?

1. $XY$
2. $X_{2}Y$
3. $X{Y}_2$
4. $X_2{Y}_3$

Q.

Why activation energy should be low in order to have higher rate of reaction?

Q.

Which of the following changes occur due to the emission of $\alpha$-particle from an atom of an element?

1. Atomic number and mass number increase by 2 units and 4 units, respectively.

2. Atomic number and mass number decrease by 2 units and 4 units, respectively.

3. Only atomic number increases by one unit.

4. Only atomic number decreases by one unit.

Q. ${}_{84}P{o}^{210}$ (half-life= 138.4 days) undergoes $\alpha$- decay to form ${}_{82}P{b}^{206}$. If 2.1 g of ${}_{84}P{o}^{210}$ is placed in a sealed tube, what volume (in mL) of helium will accumulate in 69.2 days at STP?(take $\sqrt{2}$=1.4).

Q. $\alpha$- particles can be detected using

1. Zinc sulphide screen
2. Barium sulphate
3. Thin aluminum sheet

4. Gold foil

Q.

"When an electron is removed from a sodium atom ($\mathrm{Na}$), sodium ion (${\mathrm{Na}}^{+}$) is formed". Is this statement correct? If not, correct it.

Q. 77. What is the ratio of average molecular kinetic energy of UF6 to that of H2 both at 300k?

Q. Among the radioactive elements tritium is used as better tracer because

1. It emits low energy -rays
2. It does not emit -rays
3. It is cheaply available
4. All the above

Q. The number of neutrons in deuterium is

1. 2
2. 3
3. 1
4. 0

Q. When E^° Ag+ I Ag 0.80 volt & Zn+2\vert Zn=0.76 volt , which of the following is correct? 1)Ag+ can be reduced by H2. 2)Ag can oxidise H2 into H+ion 3) Zn+2 can be reduced by H2. 4) Ag can reduce Zn+2 ion

Q. $1.0\text{g}$ atom of an $\alpha$ − emitting isotope $(t_{1/2}=10\text{days})$ is sealed in a container. The volume of the gas accumulated in the container at STP after 10 days would be:

1. $1.0\text{L}$
2. $44.8\text{L}$
3. $11.2\text{L}$
4. $22.4\text{L}$

Q. The element Lawrencium ${(}_{103}^{256}Lr)$ is named after Ernest Lawrence, whose invention - the cyclotron - helped discover many radioactive nuclei. Consider now, the alpha decay of ${}_{103}^{256}Lr$.
${}_{103}^{256}Lr{\to }_b^{a}Md+\alpha$
Where $\alpha$ represents the alpha particle given out. What are the values of a and b?

1. a=252 ; b =105
2. a=260 ; b =101
3. a=260 ; b =105
4. a=252 ; b =101

Q. Which of the following is not correct?

1. ${}_{20}^{40}Ca$ and ${}_{18}^{40}Ar$ are isotones
2. Nuclei of atoms participate in nuclear reactions
3. $1$ amu of mass defect is approximately equal to $931.5$ MeV
4. Uranium $\left(U^{238}\right)$ series is known as $(4n+2)$ series

Q.

Calculate the number of α- and β-particles emitted when ${}_{92}{U}^{238}$ changes into radioactive ${}_{82}P{b}^{206}.$
(IIT-JEE, 2000)

1. 3, 4
2. 4, 3
3. 6, 8
4. 8, 6

Q.

If N₀ active nuclei become $\frac{N_o}{16}$ in 80 days. Find the half-life of nuclei?

1. 40 days

2. 20 days

3. 60 days

4. 30 days

Q. A counter rate meter is used to measure the activity of a radioactive sample. At a certain instant, the count rate was recorded as $475$ counters per minute. Five minutes later, the count rate recorded was $270$ counts per minute. Calculate the decay constant and half life period of the sample.

Q. Which of the following are isoelectronic as well as isostructural?

1. $N{O}_3^{-}$ and $C{O}_3^{2-}$
2. $S{O}_3$ and $N{O}_3^{-}$
3. $Cl{O}_3^{-}$ and $C{O}_3^{2-}$
4. $C{O}_3^{2-}$ and $S{O}_3$

Q. $A_Z^M\to B_{Z-1}^{M-12}$
The number of $\alpha$ and $\beta$ particles emitted in the above conversion is

1. $3\alpha ,5\beta$
2. $5\alpha ,6\beta$
3. $\alpha ,3\beta$
4. $2\alpha ,4\beta$

Q. The $\alpha$-particle is identical with

1. Helium nucleus
2. Hydrogen nucleus
3. Electron
4. Proton

Q. Which of the following is expected to have the highest hydration energy?

1. 
2. 
3. 
4. 

Q.

A radioactive material decreases by simultaneous emissions of two particles with half life 1620 and 810 years. The time after which (1/4)th of the material remained is:

1. 1080 years
2. 2000years
3. 1500years
4. 1200years

Q. A radioactive substance does not emit :

1. positron
2. proton
3. $\alpha -$ rays
4. $\beta -$ rays

Q. ${}_{84}P{o}^{210}$ (half-life= 138.4 days) undergoes $\alpha$- decay to form ${}_{82}P{b}^{206}$. If 2.1 g of ${}_{84}P{o}^{210}$ is placed in a sealed tube, what volume (in mL) of helium will accumulate in 69.2 days at STP?(take $\sqrt{2}$=1.4).

Q. At a given instant there are 25 % undecayed radioactive nuclei in a sample. After 10 sec the number of undecayed nuclei remains 12.5 %. Calculate :
( i ) mean $-$ life of the nuclei and
( ii ) The time in which the number of undecayed nuclears will further reduce to 6.25 % of the reduced number.

1. ( i )$t_{means}=14.43s$ ( ii ) 40 seconds
2. ( i )$t_{means}=1.443s$ ( ii ) 40 seconds
3. ( i )$t_{means}=14.43s$ ( ii ) 4 seconds
4. None of these

Q. The disintegration rate of a certain radioactive sample at any instant is 4750 dpm. Five minutes later, the rate becomes 2700 dpm. The half life of sample is :

1. 8.13 min
2. 5.13 min
3. 4.13 min
4. 6.13 min

Q. 8. If the amount of radioactive substance is increased three times, the number of disintegrated atoms per unit time would?