21) Which among the following is a photosensitive substance?

a) Silver chloride
b) Nickel chloride
c) Copper chloride
d) Manganous chloride

ANSWER : Silver chloride

22) Zinc is:

a) a reducing agent
b) Oxidising agent
c) Both oxidising and reducing agent
d) Neither oxidising nor reducing.

ANSWER : a reducing agent

23) The aqueous solution of which salt is coloured:

a) Co(NO₃)₂

b) Zn (NO₃)₂

c) CrCl₃

d) Both a and c

ANSWER : Both a and c

24) Mercury is the only metal which is liquid at 0°C because it has:

a) High atomic mass
b) High vapour pressure
c) Very high ionization energy and weak metallic bond.
d) None of these

ANSWER : Very high ionization energy and weak metallic bond.

25) CuO when added to glass imparts blue colour. In CuO, Cu is present in ……………. Oxidation state.

a) Cu⁺
b) Cu²⁺
c) Cu
d) None of these

ANSWER : Cu²⁺

26) Which of the following element has the lowest melting and boiling point?

a) Cu
b) Mn
c) Zn
d) Ti

ANSWER : Zn

27) The lanthanide contraction is related to:

a) Density
b) Valence electrons
c) Ionic radii
d) Nuclear masses of the various members of the series.

ANSWER : Ionic radii

28) Zn²⁺ ion is colourless due to:

a) Presence of unpaired electrons.
b) Absence of unpaired electrons.
c) Repulsion by magnetic field.
d) None of these. ANSWER :

ANSWER : Absence of unpaired electrons.

29) Isotope of which metal is used in cancer therapy?

a) Co
b) Ra
c) Ni
d) Po

ANSWER : Co

30) Which among the following show variable oxidation states?

a) Zn
b) Cd
c) Hg
d) All of these.

ANSWER : All of these. 

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