Law of Radioactivity

Q.

The weight of one atom of uranium is 238 amu its actual weight in gm is?

Q. The pressure exerted by $6.0\text{g}$ of methane gas in a $0.03{\text{m}}^3$ vessel at ${129}^{\circ }\text{C}$ is $($Atomic masses : $C=12.01,H=1.01$ and $R=8.314{\text{JK}}^{-1}{\text{mol}}^{-1}$$)$

1. $31684\text{Pa}$
2. $215216\text{Pa}$
3. $13409\text{Pa}$
4. $41647\text{Pa}$

Q.

What is electrochemical equivalence and equivalent weight?

Q.

Calculate the number of gold atoms in 300 mg of a gold ring of 20-carat gold.

Q.

During nuclear explosion one of the products is ${}^{90}Sr$ with half-life of 28.1 yr. If $1\mu g$ of ${}^{90}Sr$ was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 yr and 60 yr if it is not lost metabolically?

Q. The pressure exerted by a non- reactive gaseous mixture of $6.4g$ of methane and $8.8g$ of carbon dioxide in a $10L$ vessel at ${27}^{\circ }$C is ____$kPa$
(Round off to the Nearest Integer).
[Assume gases are ideal, $R=8.314Jmo{l}^{-1}{K}^{-1}$
Atomic masses : $C=12.0u,H:1.0u,O:16.0u$]

Q.

Define radioactive decay and give some examples of it.

Q. The sulphate contains 9.87 % of M . this sulphate is isomorphous with ZNSO4.7H2O the atomic weight of M is :

Q. 5 Half life for radioactive 14c is 5760 years . ln how many years 200mg of 14c will be reduce to 25mg??

Q. 27. 5 mg radioactive sample 90% disintegrate in3 years then 99% disintegration will be in(2) 3.1 years(1) 3 years(4) 9 years(3) 6 years

Q. A spherical balloon of radius 3 cm containing helium gas has a pressure of $48\times {10}^{-3}$ bar. At the same temperature, the pressure of a spherical balloon of radius 12 cm containing the same amount of gas will be $\times {10}^{-6}$ bar.

Q.

If 32 g of $O_2$ contains 6.022 $\times {10}^{23}$ molecules at NTP then 32 g of S, under the same conditions, will contain,

1. 12.044 x 10²³ S

2. 1 x 10²³ S

3. 6.022 x 10²³ S

4. 3.011 x 10²³ S

Q.

Two radioactive elements X and Y have decay constants$\lambda$ and $10\lambda$ respectively. If decay begins with the same number of atoms of them, the ratio of atoms of X to those of Y after time $\frac{1}{9\lambda }$ will be

1. $e^2$

2. $e^{-1}$

3. $e^{-2}$

4. $e$

Q.

4g of metal oxide contains 1.6g oxygen, then equivalent mass of the metal is

Q. The radioactive decay $B{i}_{83}^{211}\to T{l}_{81}^{207}$, takes place in a $100\text{L}$ closed vessel at ${27}^{\circ }C$. Starting with 2 moles of $B{i}_{83}^{211}$ ($t_{1/2}$ = 130 seconds), the pressure developed in the vessel after 520 seconds will be:

1. $\text{1.875 atm}$
2. $\text{0.2155 atm}$
3. $\text{0.4618 atm}$
4. $\text{4.618 atm}$

Q.

What will be the mass of 10 mole of H3po4?

Q. What will be the mass of one atom of ${}^{12}C$:

1. $1.6603\times {10}^{-22}g$
2. $6amu$
3. $1.9923\times {10}^{-23}g$
4. $1amu$

Q. A radioactive isotope has a half-life of 10 days. If today 125 mg is left over, what was its original weight 40 days earlier

1. 1 g
2. 1.5 g
3. 600 mg
4. 2 g

Q. A radioactive sample had an initial activity of 56 dpm. After 69.3 minutes, it was found to have an activity of 28 dpm. Find the number of atoms in a sample that has an activity of 100 dpm.

1. 693
2. 100
3. 1000
4. 10, 000

Q. The activity of a radioactive nuclide $\left(X^{100}\right)$ is $6.023$ curie at a certain time $‘t^{\prime }$. If its disintegration constant is $3.7\times {10}^4{s}^{-1}$ the mass of $X$ after t sec is:

1. $6.022\times {10}^{6}g$
2. ${10}^{-15}g$
3. ${10}^{-13}g$
4. ${10}^{-17}g$

Q.

Calculate the weight of 0.1 moles of Na_{​​​​​2}​CO₃ ?

Q. Half-life period of a radioactive nucleus is $3$ hours. In $9$ hours its activity will be reduced by:

1. $\frac{7}{8}$
2. $\frac{1}{6}$
3. $\frac{1}{9}$
4. $\frac{1}{8}$

Q.

During the nuclear explosion, one of the products is ${}^{90}Sr$ with half of $6.93years$. If $1\mu g$ of ${}^{90}Sr$ was absorbed in the bones of a newly born baby in place of $Ca$, how much time, in years, is required to reduce it by $90\%$ if it is not lost metabolically

Q. A mixture of $N_2$ and $O_2$ gases in a cylinder contains $7\text{g}$ of $N_2$ and $8\text{g}$ of $O_2$. If the total pressure of the mixture of the gases in the cylinder is $12\text{bar}$, then the partial pressure of $N_2$ is:
[Use atomic masses, $N=14\text{u},O=16\text{u}$]

1. $12\text{bar}$
2. $6\text{bar}$
3. $4\text{bar}$
4. $9\text{bar}$

Q. A radioactive substance (parent) decays to its daughter element, the age of radioactive substance (t) is related to the daughter (d)/parent (p) ratio by the equation:

1. $t=\frac{1}{\lambda }\ln (1+\frac{d}{p})$
2. $t=\frac{1}{\lambda }\ln (1+\frac{p}{d})$
3. $t=\frac{1}{\lambda }\ln \left(\frac{d}{p}\right)$
4. $t=\frac{1}{\lambda }\ln \left(\frac{p}{d}\right)$

Q.

What is the mass of one formula unit of Nickel Fluoride?

Q. The coulombs of electricity required for reduction of 1 mole of $Mn{O}_4^{-}$ to $M{n}^{2+}$ are

1. $96500C$
2. $4.83\times {10}^{5}C$
3. $9365\times {10}^{6}C$
4. $1.93\times {10}^{5}C$

Q. An old sample of wood from an archaeological excavation was found to have a radioactivity of about 140.8 counts per minute due to ${}^{14}C(t_{1/2}=5730$ years) as against 281.6 counts per minute for that of a freshly cut piece of wood. What is the age of the old sample of wood (in millennia, 1 millennium= 1000 years)?

Q. The activity of a radioactive nuclide $\left(X^{100}\right)$ is $6.023$ curie at a certain time $‘t^{\prime }$. If its disintegration constant is $3.7\times {10}^4{s}^{-1}$ the mass of $X$ after t sec is:

1. $6.022\times {10}^{6}g$
2. ${10}^{-13}g$
3. ${10}^{-15}g$
4. ${10}^{-17}g$

Q. The group number of the element with atomic number 96 is 3.