Nuclear Chemistry - MCQ - One answer only

1. Rutherford’s scattering experiment is related to the size of the

a. atom
b. nucleus
c. electron
d. neutron

Answer (b)

2. Heavy water is

a. H₂¹⁸O
b. D₂O
c. water obtained by repeated distillation
d. water at 4°C

(JEE 1983)

Ans: (b)

3. The radiation from a naturally occurring radioactive substance, as seen after deflection by a magnetic field in one direction, are:

a. definitely alpha rays
b. definitely beta rays
c. both alpha and beta rays
d. either alpha or beta rays
(JEE 1984)

Ans: (d)

Both alpha and beta rays are deflected by magnetic field.

4. The increasing order (lowest) first for the values of e/m (charge/mass) for electron e, proton p, neutron n and alpha particle α is:

a. n, α,p,e
b. e,p,n, α
c. n,p,e, α
d. n,p, α,e
(JEE 1984)

Ans: a

Reason: Charge for neutron is zero hence e/m = 0 for neutron.
For alpha particle> It has two protons and two neutrons. Hence charge is equal to charge of two protons and mass is equal to mass of 4 protons. Hence in comparison to proton e/m, alpha particle’s e/m is 2e/4m which is equal to 0.5e/m. Electron has the same charge as proton but of different sign, but its mass is very low. Hence compared to proton its e/m is very high.

5. The radius of an atomic nucleus is of the order of:

a. 10^-10cm
b. 10^-8cm
c. 10^-13cm
d.10^-15cm
(JEE 1985)

Answer: ( c)

6. electromagnetic radiation with maximum wavelength

a. infrared
b. radiowave
c. ultraviolet
d. X-ray
(JEE 1985)

Answer (b)

Wavelength of radio waves is greater than infraredwaves.

7. Rutherford’s alpha particle scattering experiment eventually led to the conclusion that

a. mass and energy are related.
b. electrons occupy space around the nucleus.
c. neutrons are buried deep in the nucleus.
d. the point of impact with matter can be precisely determined.
(JEE 1986)

answer (b)

8. The ratio of energy of a photon of 2000 A° wavelength radiation to that of 4000A° is:

a. ¼
b. 4
c ½
d. 2
(JEE 1986)

Answer (d)

9. The half life period of a radioactive element is 140 days. After 560 days, one gram of the element will reduce to:

a. 1/16 g
b. 1/8 g
c. ¼ g
d. ½ g
(JEE 1986)
answer: (a)

Nuclear Chemistry - True - False Type Questions

1. Gamma rays are electromagnetic radiations of wavelengths of 10^-6 to 10^-5 cm. (1983)

Ans: False

2. In β-emission from a nuclues the atomic number of the daughter element decreases by one. (JEE 1990).

Answer: False

In β-emission, number of protons in the nucleus goes up by one.

3. In a given electric field, β-particles are deflected more than α-particles having larger charge. (JEE 1993)

True

The deflection of the particle depends on the acceleration produced in it. The acceleration depends on the force and mass. Thus, in case of electric field it depends on the e/m of the particles. For β-particles, e/m is larger than α-particles because electrons are very very light than He⁺ species. So charge on helium particle is only twice high but mass is very very high.

Nuclear Chemistry - Fill Blanks Type

1. An element under [A,Z]M undergoes an α-emission followed by two successive β-emissions. The element formed is __________ . (JEE 1982)

answer: [A-4, Z]M
Refer:
α-emission
β-emission

2. The number of neutrons in the parent nucleus which gives ¹⁴N on beta emission is __________ . (JEE 1985)

Answer: 8
Reason: One proton increases to give 7 protons of nitrogen. Hence before beta emission there are 8 neutrons and 6 protons.

3. A radio active nucleus decays emitting one alpha and two beta particles; the daughter nucleus is ___________ of the parent. (JEE 1989)

Answer: isotope
Reason; Z is same but A is different.