Problem 138
Half-life of a substance A, following first order kinetics is 5 days. Starting with \(100 \mathrm{~g}\) of \(\mathrm{A}\), amount left after 15 days is (a) \(25 \mathrm{~g}\) (b) \(50 \mathrm{~g}\) (c) \(12.5 \mathrm{~g}\) (d) \(6.25 \mathrm{~g}\)
Problem 139
\(\beta\) particle is emitted in a radioactive reaction when [2002] (a) a proton changes to neutron (b) a neutron changes to proton (c) a neutron changes to electron (d) an electron changes to neutron
Problem 140
The radio nucliede \({ }_{90}\) Th \(^{234}\) undergoes two successive \(\beta\) decays followed by one \(\alpha\) decay. The atomic number and the mass number respectively of the resulting radio nucliede will be (a) 92 and 234 (b) 94 and 230 (c) 90 and 230 (d) 92 and 230
Problem 141
The half-life of a radioactive isotope is three hours. If the initial mass of the isotope were \(256 \mathrm{~g}\), the mass of it remaining undecayed after 18 hours would be [2003] (a) \(4.0 \mathrm{~g}\) (b) \(8.0 \mathrm{~g}\) (c) \(12.0 \mathrm{~g}\) (d) \(16.0 \mathrm{~g}\)
Problem 142
Consider the following nuclear reactions \({ }_{92} \mathrm{M}^{238} \longrightarrow \mathrm{y}^{\mathrm{N}}^{\mathrm{x}}+2{ }_{2} \mathrm{He}^{4}\) \({ }_{\mathrm{y}} \mathrm{N}^{\mathrm{x}} \longrightarrow{\mathrm{B}} \mathrm{L}^{\mathrm{A}}+2 \beta^{+}\) The number of neutrons in element \(\mathrm{L}\) is (a) 146 (b) 144 (c) 142 (d) 140
Problem 143
The half-life of a radio isotope is four hours. If the initial mass of the isotope was \(200 \mathrm{~g}\) the mass remaining undecayed after 24 hours is (a) \(2.084 \mathrm{~g}\) (b) \(3.125 \mathrm{~g}\) (c) \(4.167 \mathrm{~g}\) (d) \(1.042 \mathrm{~g}\)
Problem 144
A photon of hard \(\gamma\) radiation knocks a proton out of \({ }_{12} \mathrm{Mg}^{44}\) nucleus to form (a) the isotope of parent nucleus (b) the isobar of parent nucleus (c) the nuclide of \({ }_{14} \mathrm{Na}^{23}\) (d) the isobar of \(_{11} \mathrm{Na}^{23}\)
Problem 145
Hydrogen bomb is based on the principle of (a) artificial radioactivity (b) nuclear fission (c) nuclear fusion (d) natural radioactivity
Problem 146
In the transformation of \(_{92} \mathrm{U}^{238}\) to \({ }_{92} \mathrm{U}^{234}\), if one emission is an \(\alpha\) particle, what should be the other emission(s)? \([2006]\) (a) two \(\beta\) (b) two \(\beta^{-}\)and one \(\beta^{+}\) (c) one \(\beta\) - and one \(\gamma\) (d) one \(\beta^{-}\)and one \(\beta^{-}\)
Problem 147
A radioactive element gets spilled over the floor of a room. Its half-life period is 30 days. If the initial activity is ten times the permissible value, after how many days will it be safe to enter the room? (a) 300 days (b) 10 days (c) 100 days (d) 1000 days
