Chemistry for competitive exams – 03

1. The number of isotopes in which hydrogen can exit are –

(a)  1   (b)   4  (c) 3  (d) 2

Ans. (c) 3

 

2. The differences between isotopes of an element is due to the presence of different number of

(a)  protons   (b) neutrons      (c) electrons   (d) photons

Ans. (b) neutrons  

3. In order to lower the temperature below 0⁰ C, the substances mixed with ice is

(a) sodium chloride      (b) sodium carbonate    (c) magnesium sulphate    (d) lime

Ans. (a) sodium chloride  

4. The material which can be deformed permanently by heat and pressure is called a --- thermoplastic

5. When a gold sheet is bombarded by a beam of alfa-particles only a few of them get deflected whereas most go straight, un deflected. This is because

(a) the forces of attraction exerted on the alfa-particulars by the oppositely charged electrons is not sufficient

(b) a nucleus has a much smaller volume than that of an atom

(c) the forces of repulsion acting on the fast-moving alfa- particles is very small

(d) the neutrons in the nucleus do not have any effect on the alfa-particles

Ans. (b) a nucleus has a much smaller volume than that of an atom

6. Rutherford’s scattering formula fails for very small scattering angles because

(a)The full nuclear charge of the target atom is partially screened by its electron

(b) The impact parameter between the alfa-particle source and the nucleus of the target is very large compared to the size of the nucleus

(c) the kinetic energy of the alfa-particle is large

(d) both (a) and (b)

Ans. (d) both (a) and (b)

7. Which of the following statement is not true for anode rays?

(a)They are deflected by electron and magnetic fields

(b) Their e/m ratio depends on the gas I the Discharge tube used to produce the anode rays

(c) The e/m ratio of anode rays is constant

(d) They are produced by the ionization of the gas in Discharge Tube

Ans. (c) The e/m ratio of anode rays is constant

8. Rutherford’s alfa-particle scattering experiment led to the conclusion that

(a) mass and energy are related

(b) the mass and the positive charge of an atom are concentrated in the nucleus

(c) neutrons are present in the nucles

(d) atoms are electrically neutral

Ans. (b) the mass and the positive charge of an atom are concentrated in the nucleus

9. Photo-oxidation process is initiated by

(a) heat   (b) light   (c) catalyst    (d) oxygen

Ans. (b) light

10. In halogens which of the following increases feon iodine to fluorine?

(a) electro negativity

(b) the first ionization potential of the element

(c) oxidizing power

(d) all the above

Ans. (d) all the above